Bites and Stings

Definition

Humans can be injured by the bites or stings of many kinds of animals, including mammals such as dogs, cats, and fellow humans; arthropods such as spiders, bees, and wasps; snakes; and marine animals such as jellyfish and stingrays.

Description

Mammals

DOGS. In the United States, where the dog population exceeds 50 million, dogs surpass all other mammals in the number of bites inflicted on humans. However, most dog-bite injuries are minor. A telephone survey of U.S. households conducted in 1994 led researchers to estimate that 3,737,000 dog bites not requiring medical attention occurred in the United States that year, versus 757,000 that required medical treatment. Studies also show that most dog bites are from pets or other dogs known to the bitten person, that males are more likely than females to be bitten, and that children face a greater risk than adults. Each year, about 10-20 Americans, mostly children under 10 years of age, are killed by dogs.

Dog bites result in an estimated 340,000 emergency room visits annually throughout the United States. More than half of the bites seen by emergency departments occur at home. Children under 10 years old, especially boys between 5 and 9 years of age, are more likely than older people to visit an emergency room for bite treatment. Children under 10 years old were also much more liable to be bitten on the face, neck, and head. Nearly all of the injuries suffered by people seeking treatment in emergency rooms were of "low severity," and most were treated and released without being admitted to the hospital or sent to another facility. Many of the bites resulted from people attempting to break up fights between animals.

CATS. Although cats are found in nearly a third of U.S. households, cat bites are far less common than dog bites. According to one study, cats inflict perhaps 400,000 harmful bites in the United States each year. The tissue damage caused by cat bites is usually limited, but they carry a high risk of infection. Whereas the infection rate for dog bite injuries is 15-20%, the infection rate for cat bites is 30-40%.

HUMANS. Bites from mammals other than dogs and cats are uncommon, with one exception—human bites. There are approximately 70,000 human bites each year in the United States. Because the human mouth contains a multitude of potentially harmful microorganisms, human bites are more infectious than those of most other animals.

Arthropods

Arthropods are invertebrates belonging to the phylum Arthropoda, which includes insects, arachnids, crustaceans, and other subgroups. There are more than 700,000 species in all. The list of arthropods that bite or sting humans is extensive and includes lice, bedbugs, fleas, mosquitoes, black flies, ants, chiggers, ticks, centipedes, scorpions, and other species. Spiders, bees, and wasps are the three kinds of arthropod that most often bite people.

SPIDERS. In the United States, only two kinds of venomous spider are truly dangerous: widow spiders and brown (violin or fiddle) spiders. The black widow, which is found in every state but Alaska, is probably the most notorious widow spider. It prefers dark, dry places such as barns, garages, and outhouses, and also lives under rocks and logs. Disturbing a female black widow or its web may provoke a bite. Brown spiders also prefer sheltered places, including clothing, and may bite if disturbed.

BEES AND WASPS. Bees and wasps will sting to defend their nests or if they are disturbed. Species common to the United States include honeybees, bumblebees, yellow jackets, bald-faced hornets, brown hornets, and paper wasps. Of note are also Africanized bee species, also called "killer bees" that have been found in the United States since 1990. More than 50 Americans die each year after being stung by a bee, wasp, or ant. Almost all of those deaths are the result of allergic reactions, and not of exposure to the venom itself.

Snakes

There are 20 species of venomous snakes in the United States. These snakes are found in every state except Maine, Alaska, and Hawaii. Each year about 8,000 Americans receive a venomous snakebite, but no more than about 15 die, mostly from rattlesnake bites.

The venomous snakes of the United States are divided into two families, the Crotalidae (pit vipers) and the Elapidae. Pit vipers, named after the small heat-sensing pit that lies between each eye and nostril, are responsible for about 99% of the venomous snakebites suffered by Americans. Rattlesnakes, copperheads, and cottonmouths (also called water moccasins) are pit vipers. This family of snakes delivers its venom through two long, hinged fangs in the upper jaw. Some pit vipers carry a potent venom that can threaten the brain and spinal cord. The venom of others, such as the copperheads, is less harmful.

The Elapidae family includes two kinds of venomous coral snakes indigenous to the southern and western states. Because coral snakes are bashful creatures that come out only at night, they almost never bite humans, and are responsible for approximately 25 bites a year in the United States. Coral snakes also have short fangs and a small mouth, which lowers the risk of a bite actually forcing venom into a person's body. However, their venom is quite poisonous.

Marine animals

Several varieties of marine animal may bite or sting. Jellyfish and stingrays are two kinds that pose a threat to people who live or vacation in coastal communities.

Causes and symptoms

Mammals

DOGS. A typical dog bite results in a laceration, tear, puncture, or crush injury. Bites from large, powerful dogs may even cause fractures and dangerous internal injuries. Also, dogs trained to attack may bite repeatedly during a single episode. Infected bites usually cause pain, cellulitis (inflammation of the connective tissues), and a pus-filled discharge at the wound site within 8-24 hours. Most infections are confined to the wound site, but many of the microorganisms in the mouths of dogs can cause systemic and possibly life-threatening infections. Examples are bacteremia and meningitis, especially severe in people diagnosed with acquired immunodeficiency syndrome (AIDS ) or other health condition that increases their susceptibility to infection. Rabies is rare among pet dogs in the United States, most of which have been vaccinated against the disease. Tetanus is also rare but can be transmitted by a dog bite if the victim is not immunized.

CATS. The mouths of cats and dogs contain many of the same microorganisms. Cat scratches and bites are also capable of transmitting the Bartonella henselae bacterium, which can lead to cat-scratch disease, an unpleasant but usually not life-threatening illness.

Cat bites are mostly found on the arms and hands. Sharp cat teeth typically leave behind a deep puncture wound that can reach muscles, tendons, and bones, which are vulnerable to infection because of their comparatively poor blood supply. This is why cat bites are much more likely to become infected than dog bites. Also, people are less inclined to view cat bites as dangerous and requiring immediate attention; the risk that infection has set in by the time a medical professional is consulted is thus greater.

HUMANS. Humans bites result from fights, sexual activity, medical and dental treatment, and seizures. Bites also raise the possibility of spousal or child abuse. Children often bite other children, but those bites are hardly ever severe. Human bites are capable of transmitting a wide range of dangerous diseases, including hepatitis B, syphilis, and tuberculosis.

Human bites fall into two categories: occlusional (true) bites and clenched-fist injuries. The former present a lower risk of infection. The latter, which are very infectious and can permanently damage the hand, usually result from a fist hitting teeth during a fight. People often wait before seeking treatment for a clenched-fist injury, with the result that about half of such injuries are infected by the time they are seen by a medical professional.

Arthropods

SPIDERS. As a rule, people rarely see a black widow bite, nor do they feel the bite as it occurs. The first (and possibly only) evidence that a person has been bitten may be a mild swelling of the injured area and two red puncture marks. Within a short time, however, some victims begin to experience severe muscle cramps and rigidity of the abdominal muscles. Other possible symptoms include excessive sweating, nausea, vomiting, headaches, and vertigo as well as breathing, vision, and speech problems.

A brown spider's bite can lead to necrotic arachnidism, in which the tissue in an area of up to several inches around the bite becomes necrotic (dies), producing an open sore that can take months or years to disappear. In most cases, however, the bite simply produces a hard, painful, itchy, and discolored area that heals without treatment in 2-3 days. The bite may also be accompanied by a fever, chills, edema (an accumulation of excess tissue fluid), nausea and vomiting, dizziness, muscle and joint pain, and a rash.

BEES AND WASPS. The familiar symptoms of bee and wasp stings include pain, redness, swelling, and itchiness in the area of the sting. Multiple stings can have much more severe consequences, such as anaphylaxis, a life-threatening allergic reaction that occurs in hypersensitive persons.

Snakes

Venomous pit viper bites usually begin to swell within 10 minutes and sometimes are painful. Other symptoms include skin blisters and discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Severe poisoning can also lead to tingling in the scalp, fingers, and toes, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure, vomiting of blood, and coma.

Many pit viper and coral snake bites (20-60%) fail to poison (envenomate) their victim, or introduce only a small amount of venom into the victim's body. The wounds, however, can still become infected by the harmful microorganisms that snakes carry in their mouths.

KEY TERMS

Anaphylaxis— A life-threatening allergic reaction occurring in persons hypersensitive to bites and stings.

Antibiotics— Substances used against bacteria that cause infection.

Antibodies— Substances created by the body to combat infection.

Antihistamines— Drugs used to treat allergic reactions by acting against a substance called histamine.

Arachnid— Large class of arthropods that includes spiders, scorpions, mites, and ticks. Arachnids have a segmented body divided into two parts, one of which has four pairs of legs but no antennae.

Arachnidism— Poisoning resulting from the bite or sting of an arachnid.

Bacteremia— Bacteria in the blood.

Blood serum— A component of blood.

Immune system— The body system that fights infection and protects the body against foreign invaders and disease.

Killer bees— Hybrids of African bees accidentally introduced into the wild in South and North America in 1956 and first reported in Texas in 1990. They were first imported by Brazilian scientists attempting to create a new hybrid bee to improve honey production.

Lymph nodes— Small, kidney-shaped organs that filter a fluid called lymph and that are part of the body's immune system.

Pus— A thick yellowish or greenish fluid composed of the remains of dead white blood cells, pathogens and decomposed cellular debris.

Coral snake bites are painful but may be hard to see. One to seven hours after the bite, a bitten person begins to experience the effects of the venom, which include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Major nerves of the body can become paralyzed for 6-14 days, causing double vision, difficulty swallowing and speaking, respiratory failure, and other problems. Six to eight weeks may be needed before normal muscular strength is regained.

Marine animals

JELLYFISH. Jellyfish venom is delivered by barbs called nematocysts, which are located on the creature's tentacles and penetrate the skin of people who brush up against them. Instantly painful and itchy red lesions usually result. The pain can continue up to 48 hours. Severe cases may lead to skin necrosis, muscle spasms and cramps, vomiting, nausea, diarrhea, headaches, excessive sweating, and other symptoms. In rare instances, cardiorespiratory failure may also occur.

STINGRAYS. Tail spines are the delivery mechanism for stingray venom. Deep puncture wounds result that can cause an infection if pieces of spine become embedded in the wound. A typical stingray injury scenario involves a person who inadvertently steps on a resting stingray and is lashed in the ankle by its tail. Stingray venom produces immediate, excruciating pain that lasts several hours. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhage (bleeding), a drop in blood pressure, and cardiac arrhythmia (disordered heart beat).

Diagnosis

Mammals

DOGS. Gathering information on the circumstances of a dog attack is a crucial part of treatment. Medical professionals need to know when the attack occurred (the chances of infection increase dramatically if the wound has been left untreated for more than eight hours) and what led to the attack (unprovoked attacks are more likely to be associated with rabies). A person's general health must also be assessed, including the tetanus immunization history if any, as well as information concerning possible allergies to medication and pre-existing health problems that may increase the risk of infection.

A physical examination requires careful scrutiny of the wound, with special attention to possible bone, joint, ligament, muscle, tendon, nerve, or blood-vessel damage caused by deep punctures or severe crush injuries. Serious hand injuries should be evaluated by a specialized surgeon. Most of the time, laboratory tests for identifying the microorganisms in bite wounds are performed if infection is present. X rays and other diagnostic procedures may also be necessary.

CATS. The diagnostic procedures used for dog bites also apply to cat bites.

HUMANS. Testing the blood of a person who has been bitten for immunity to hepatitis B and other diseases is always necessary after a human bite. Ideally, the biter should be tested as well for the presence of transmissible disease. Clenched-fist injuries often require evaluation by a hand surgeon or orthopedist. Because many people will deny having been in a fight, medical professionals usually consider lacerations over the fourth and fifth knuckles—the typical result of a clenched-fist injury—to be evidence of a bite wound. Medical professionals also look for indications of spousal or child abuse when evaluating human bites.

Arthropods

SPIDERS. Because bites from widow spiders and brown spiders require different treatments, capturing and identifying the spider helps to establish diagnosis.

Snakes

Diagnosis relies on a physical examination of the victim, information about the circumstances of the bite, and a look at the snake itself (if it can safely be killed and brought in for identification). Blood tests and urinalysis supply important data on the victim's condition. Chest x-rays and electrocardiography (a procedure for measuring heart activity) may also be necessary.

Treatment

Mammals

DOGS. Minor dog bites can be treated at home. The American Academy of Family Physicians recommends gently washing the wound with soap and water and then applying pressure to the injured area with a clean towel to stop the bleeding. The next step is to apply antibiotic ointment and a sterile bandage to the wound. To reduce swelling and fend off infection, ice should be applied and the injured area kept elevated above the level of the heart. The wound should be cleaned and covered with ointment twice a day until it heals.

Any dog bite that does not stop bleeding after 15 minutes of pressure must be seen by a medical professional. The same is true for bites that are deep or gaping; for bites to the head, hands, or feet; and for bites that may have broken a bone, damaged nerves, or caused a major injury of another kind. Bite victims must also watch for infection. A fever is one sign of infection, as are redness, swelling, warmth, increased tenderness, and pus at the wound site. Diabetics, people with AIDS or cancer, individuals who have not had a tetanus shot in five years, and anyone else who has a medical problem that can increase susceptibility to infection should seek medical treatment no matter how minor the bite appears.

Medical treatment of dog bites involves washing the wound with an anti-infective solution. Removal of dead and damaged tissue (under local, regional, or general anesthetic) may be required after the wound has been washed, and any person whose tetanus shots are not up to date should receive a booster injection. Some wounds are left open and allowed to heal on their own, while others require stitches (stitching may be delayed a few days if infection is a concern). Many emergency departments prescribe antibiotics for all people with dog bites, but some researchers suggest that antibiotics are usually unnecessary and should be limited to those whose injuries or other health problems make them likely candidates for infection. A follow-up visit after one or two days is generally required for anyone who has received bite treatment.

CATS. Because of the high risk of infection, people who are bitten by a cat should always see a doctor. Cat scratches do not require professional medical treatment unless the wound appears infected or the scratched person has a weakened immune system.

Medical treatment for cat bites generally follows the procedures used for dog bites. Experts advise, however, that cat-bite wounds should always be left open to prevent infection. Persons who have been bitten by cats generally receive antibiotics as a preventive measure.

HUMANS. Human bites should always be examined by a doctor. Such bites are usually treated with antibiotics and left open because of the high risk of infection. A study released in June 2004 showed that routine use of antibiotics for human bites may not be necessary, as physicians try to minimize overuse of antibiotics. Superficial wounds in low-risk areas may no longer need antibiotic treatment, but more serious human bites to high-risk areas such as the hands should be treated with antibiotics to prevent serious infection. A person who has been bitten may also require immunization against hepatitis B and other diseases. Persons who are being treated for a clenched-fist injury will require a daily follow-up examination for 3-5 days.

Arthropods

SPIDERS. No spider bite should be ignored. The antidote for severe widow spider bites is a substance called antivenin, which contains antibodies taken from the blood serum of horses injected with spider venom. Doctors exercise caution in using antivenin, however, because it can trigger anaphylactic shock, a potentially deadly (though treatable) allergic reaction, and serum sickness, an inflammatory response that can give rise to joint pain, a fever, rashes, and other unpleasant, though rarely serious, consequences.

An antivenin for brown spider bites exists as well, but it is not yet available in the United States. The drug dapsone, used to treat leprosy, can sometimes stop the tissue death associated with a brown spider bite. Necrotic areas may need debridement (removal of dead and damaged tissue) and skin grafts. Pain medications, antihistamines, antibiotics, and tetanus shots are a few of the other treatments that are sometimes necessary after a bite from a brown spider or widow spider.

BEES AND WASPS. Most stings can be treated at home. A stinger that is stuck in the skin can be scraped off with a blade, fingernail, credit card, or piece of paper (using tweezers may push more venom out of the venom sac and into the wound). The area should be cleaned and covered with an ice pack. Aspirin and other pain medications, oral antihistamines, and calamine lotion are good for treating minor symptoms. Putting meat tenderizer on the wound has no effect.

Persons who have been stung and experience an allergic reaction, or who are at risk due to their medical history, require immediate medical attention. The danger signs, which usually begin 10 minutes after an individual is stung (though possibly not for several hours), include nausea, faintness, chest pain, abdominal cramps, diarrhea, and difficulty swallowing or breathing.

Snakes

Although most snakes are not venomous, any snakebite should immediately be examined at a hospital. While waiting for emergency help to arrive, the victim should wash the wound site with soap and water, and then keep the injured area still and at a level lower than the heart. Ice should never be used on the wound site nor should attempts be made to suck out the venom. Making a cut at the wound site is also dangerous. It is important to stay calm and wait for emergency medical aid if it can arrive quickly. Otherwise, the victim should proceed directly to a hospital.

When the victim arrives at a hospital, the medical staff must determine whether the bite was inflicted by a venomous snake and, if so, whether envenomation occurred and how much venom the person has received. Patients may develop low blood pressure, abnormal blood clotting, or severe pain, all of which require aggressive treatment. Fortunately, the effects of some snakebites can be counteracted with antivenin. Minor rattlesnake envenomations can be successfully treated without antivenin, as can copperhead and water-moccasin bites. However, coral snake envenomations and the more dangerous rattlesnake envenomations require antivenin, sometimes in large amounts. Other treatment measures include antibiotics to prevent infection and a tetanus booster injection.

Marine animals

JELLYFISH. Vinegar and other acidic substances are used to neutralize jellyfish nematocysts still clinging to the skin, which are then scraped off. Anesthetic ointments, antihistamine creams, and steroid lotions applied to the skin are sometimes beneficial. Other measures may be necessary to counter the many harmful effects of jellyfish stings, which, if severe, require emergency medical care.

STINGRAYS. Stingray wounds should be washed with saltwater and then soaked in very hot water for 30-90 minutes to neutralize the venom. Afterwards, the wound should be examined by a doctor to ensure that no pieces of spine remain.

Alternative treatment

Arthropods

Several alternative self-care approaches are used to treat minor bee, wasp, and other arthropod stings, including aromatherapy, ayurvedic medicine, flower remedies, herbs, homeopathy, and nutritional therapy.

Prognosis

Mammals

Prompt treatment and recognizing that even apparently minor bites can have serious consequences are the keys to a good outcome after a mammal bite. Infected bites can be fatal if neglected. Surgery and hospitalization may be needed for severe bites.

Arthropods

SPIDERS. Even without treatment, adults usually recover from black widow bites after 2-3 days. Those most at risk of dying are very young children, the elderly, and people with high blood pressure. In the case of brown spider bites, the risk of death is greatest for children, though rare.

BEES AND WASPS. The pain and other symptoms of a bee or wasp sting normally fade away after a few hours. People who are allergic to such stings, however, can experience severe and occasionally fatal anaphylaxis.

Snakes

A snakebite victim's chances of survival are excellent if medical aid is obtained in time. Some bites, however, result in amputation, permanent deformity, or loss of function in the injured area.

Marine animals

STINGRAYS. Stingray venom kills its human victims on rare occasions.

Prevention

Mammals

DOGS. The risk of a dog bite injury can be reduced by avoiding sick or stray dogs, staying away from dogfights (people often get bitten when they try to separate the animals), and not behaving in ways that might provoke or upset dogs, such as wrestling with them or bothering them while they are sleeping, eating, or looking after their puppies. Special precautions need to be taken around infants and young children, who must never be left alone with a dog. Pit bulls, rottweilers, and German shepherds (responsible for nearly half of all fatal dog attacks in the United States in 1997–2000) are potentially dangerous pets in households where children live or visit. For all breeds of dog, obedience training as well as spaying or neutering lessen the chances of aggressive behavior.

CATS. Prevention involves warning children to stay away from strange cats and to avoid rough play and other behavior that can anger cats and cause them to bite.

Arthropods

SPIDERS. Common-sense precautions include clearing webs out of garages, outhouses, and other places favored by venomous spiders; keeping one's hands away from places where spiders may be lurking; and, when camping or vacationing, checking clothing, shoes, and sleeping areas.

BEES AND WASPS. When possible, it is advised to avoid the nests of bees and wasps and to not eat sweet food or wear bright clothing, perfumes, or cosmetics that attract bees and wasps.

Emergency medical kits containing self-administrable epinephrine to counter anaphylactic shock are available for allergic people and should be carried by them at all times. People who suspect they are allergic should consult an allergist about shots that can reduce reactions to bee and wasp venom.

Snakes

Snakes should not be kept as pets. Measures such as mowing the lawn, keeping hedges trimmed, and removing brush from the yard also discourages snakes from living close to human dwellings. Tongs should be used to move brush, lumber, and firewood, to avoid exposing one's hands to snakes that might be lying underneath. Similarly, golfers should never use their hands to retrieve golf balls from a water hole, since snakes can be hiding in the rocks and weeds. Caution is also necessary when walking through weedy or grassy areas, and children should be prevented from playing in weedy, vacant lots and other places where snakes may live. Leather boots and long pants offer hikers and campers some protection from bites. Approaching a snake, even a dead one, can be dangerous, for the venom of recently killed snakes may still be active.

Marine animals

JELLYFISH. Prevention of jellyfish stings includes obeying posted warning signs at the beach. Also, jellyfish tentacles may be transparent and up to 120 ft (36.5 m) long, therefore great caution must be exercised whenever a jellyfish is sighted nearby. An over-the-counter cream was being tested at the Stanford University School of Medicine in the summer of 2004. In early tests, it was effective in helping to prevent some jellyfish contact.

STINGRAYS. Shuffling while walking through shallow areas that may be inhabited by stingrays will disturb the water, causing the animal to move before it can be stepped on.

Resources

BOOKS

Holve, Steve. "Envenomations." In Cecil Textbook of Medicine, edited by Lee Goldman and J. Claude Bennett, 21st ed. Philadelphia: W. B. Saunders, 2000, pp. 2174-2178.

Sutherland, Struan, and Tibballs, James. Australian Animal Toxins. 2nd ed. New York, Oxford Univ Press, 2001.

PERIODICALS

"Cream May Ward Off Jellyfish." Drug Week (June 25, 2004): 553.

"Do All Human Bite Wounds Need Antibiotics?" Emergency Medicine Alert (June 2004): 3.

Graudins, A., M. Padula, K. Broady, and G. M. Nicholson. "Red-back spider (Latrodectus hasselti) antivenom prevents the toxicity of widow spider venoms." Annals of Emergency Medicine 37, no. 2 (2001): 154-160.

Jarvis R. M., M. V. Neufeld, and C. T. Westfall. "Brown recluse spider bite to the eyelid." Ophthalmology 107, no. 8 (2000): 1492-1496.

Metry, D. W., and A. A. Hebert. "Insect and arachnid stings, bites, infestations, and repellents." Pediatric Annals 29, no. 1 (2000): 39-48.

Sams, H. H., C. A. Dunnick, M. L. Smith, and L. E. King. "Necrotic arachnidism." Journal of the American Academy of Dermatology 44, no. 4 (2001): 561-573.

Sams, HH. "Nineteen documented cases of Loxosceles reclusa envenomation." Journal of the American Academy of Dermatology 44, no.4 (2001): 603-608.

ORGANIZATIONS

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. Fax: (414) 276-3349. 〈http://www.aaem.org/〉.

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 906-6000. 〈http://www.aafp.org/〉. [email protected].

American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. 〈http://www.ama-assn.org/〉.

OTHER

City of Phoenix, Arizona. 〈http://www.ci.phoenix.az.us/FIRE/bitessna.html〉.

Southwestern University School of Medicine. 〈http://www.swmed.edu/toxicology/toxlinks.html〉.

Toxicology Professional Groups. 〈http://www.pitt.edu/∼martint/pages/motoxorg.htm#AAPCC〉.

University of Sydney, Australia. 〈http://www.usyd.edu.au/su/anaes/spiders.html〉.

Vanderbilt University. 〈http://www.mc.vanderbilt.edu/clintox/〉.

Bites and stings

Definition

People can be injured by the bites or stings of many animals, including mammals such as dogs, cats, and fellow humans; arthropods such as spiders, bees, and wasps; snakes; and marine animals such as jellyfish and stingrays.

Description

Mammals

DOGS. In the United States, where the dog population exceeds 50 million, dogs surpass all other mammals in the number of bites inflicted on humans. Most come from family pets or other dogs known to the victim. Fortunately, most dog-bite injuries are minor. A 1994 telephone survey of American households indicated that there were 3,737,000 dog bites that did not require medical attention in the United States during that year, and 757,000 that did. Men and boys are more likely to be bitten than girls or women; not surprisingly, children face a greater risk than adults. Each year, about 10–20 Americans, mostly children under 10 years of age, are killed by dogs.

In the United States, dog bites send an estimated 340,000 people to the emergency room each year. Children under 10 are more likely than older people to need immediate medical treatment; this is especially true for boys between five and nine. Children under ten were also much more likely to be bitten on the face, neck, and head. Few of the injuries suffered by people seeking emergency treatment were serious; most patients were treated and released without being admitted or referred to another facility.

CATS. Although cats are found in nearly a third of American households, their bites are far less common than dog bites. According to one study, cats inflict perhaps 400,000 harmful bites in the United States each year. Cat bites typically cause less tissue damage, but they carry a higher risk of infection (30-40%) than dog bites (15-20%). Young girls are the most likely to be bitten by cats.

HUMANS. There are approximately 70,000 human bites each year in the United States. They can be just as serious a medical problem as a bite from an animal. Because the human mouth contains a multitude of potentially harmful microorganisms, these tend to become have a higher infection rate than those inflicted by animals.

Arthropods

Arthropods are invertebrates such as insects, arachnids, crustaceans, and other subgroups of the phylum Arthropoda—a group that encompasses more than 700,000 species. The list of arthropods that bite or sting is extensive and includes lice, bedbugs, fleas, mosquitoes, blackflies, ants, chiggers, ticks, centipedes, scorpions, and other creatures. Spiders, bees, and wasps are the three that people encounter most often.

SPIDERS. In the United States, only two kinds of venomous spider have a truly life-threatening bite: black widow spiders and brown recluse spiders. The black widow, which is found in every state but Alaska, is probably the most infamous widow spider. It prefers dark, dry places such as barns, garages, and outhouses, and also lives under rocks and logs. Disturbing a female black widow or her web may provoke a bite. Red widow spiders are far more rare, but can be found in parts of Florida; their sting is also quite venomous. Brown recluse spiders also prefer sheltered places, including clothing, and may bite if disturbed.

BEES AND WASPS. Bees and wasps will sting to defend their nests or if they are disturbed. Species common to the United States include honeybees, bumblebees, yellow jackets, bald-faced hornets, brown hornets, and paper wasps. More than 50 Americans die each year after being stung by a bee, wasp, or fire ant. Almost all of those deaths are caused by allergic reactions to the venom, not by its toxicity.

Snakes

There are 20 species of venomous snakes in the United States; they're found in every state except Maine, Alaska, and Hawaii. Each year about 8,000 Americans receive a venomous snakebite, but no more than about 15 die; most of the deaths are from rattlesnake bites.

The venomous snakes of the United States are divided into two families: Crotalidae (pit vipers) and Elapidae. Pit vipers, which take their name from the small heat-sensing pit that lies between each eye and nostril, are responsible for about 99% of the venomous snakebites suffered by Americans. The group includes rattlesnakes, copperheads, and cottonmouths (also called water moccasins). This type of snake delivers its venom through two long, hinged fangs in the upper jaw. Some pit vipers carry a potent, fast-acting venom that can damage the brain and spinal cord . The venom of others, such as the copperheads, is less harmful.

The Elapidae include two kinds of venomous coral snakes indigenous to the southern and western states. Because coral snakes are bashful creatures that come out only at night, they almost never bite humans, and are responsible for only about 25 bites a year in the United States. Coral snakes also have short fangs and a small mouth, which lessens the risk of a bite actually forcing venom through the skin and subcutaneous tissues into muscles or veins. However, if ingested, their venom is quite poisonous.

Marine animals

Several varieties of marine animal bite or sting, including sharks, jellyfish, stingrays, anemones, and even a few types of coral. Although only a few have venom powerful enough to kill, they can inflict painful injuries. As with spider and bee stings, allergic individuals can also have anaphylactic reactions to these bites.

Causes and symptoms

Mammals

DOGS. A typical dog bite results in a laceration, puncture, or crush injury. Infected bites usually cause pain , cellulitis (inflammation of the connective tissues), and a pus-filled discharge at the wound site within 8–24 hours. Most infections are confined to the wound site, but microorganisms in dogs' mouths can cause systemic and possibly life-threatening infections such as sepsis and meningitis , especially among people with compromised immune systems that decrease their resistance to infection. Rabies is rare among pet dogs in the United States, most of which have been vaccinated against the disease. Tetanus is also a rare complication.

CATS. Cat scratches and bites can transmit the Bartonella henselae bacterium, which can lead to catscratch disease, an uncommon and unpleasant but not usually life-threatening illness. The mouths of cats and dogs contain many of the same microorganisms, and many of the same types of infections can result.

Cat bites are mostly found on the arms and hands. Sharp cat teeth typically leave behind a deep puncture wound that can reach muscles, tendons, and bones, which are vulnerable to infection because of their comparatively poor blood supply. This is one reason why cat bites are much more likely than dog bites to become infected. People are also less inclined to give cat bites immediate medical attention, increasing the risk that infection will set in. Infected cat scratches on fingers or toes, in fact, have been known to spread inward to the bone, and result in the need for amputation of the digit.

HUMANS. Although children often bite other children, these bites are hardly ever severe. Most humans bites that require medical attention result from fights (raising the possibility of domestic or child abuse ), sexual activity, medical and dental treatment, and seizures. They can transmit a wide range of dangerous diseases, including hepatitis B, syphilis , tuberculosis , and HIV.

Human bites fall into two categories: occlusional (true) bites and clenched-fist injuries. The former present a low risk of infection. The latter, which are very infectious and can permanently damage the hand, usually result when a fist hits teeth during a fight. People often wait before seeking treatment for a clenched-fist injury, with the result that about half of such injuries are infected by the time they are seen by a medical professional.

Arthropods

SPIDERS. People do not always feel a black widow's bite. The first (and possibly only) evidence that a person has been bitten may be a mild swelling of the injured area and two red puncture marks showing where the spider's fangs entered the skin. Within a short time, however, some victims begin to experience severe muscle cramps and rigid abdominal muscles. Other possible symptoms include excessive sweating, nausea, vomiting, headaches, and vertigo as well as breathing, vision , and speech problems.

A brown recluse spider's bite can lead to necrotic arachnidism, in which the tissue in an area of up to several inches around the bite becomes necrotic, producing an open sore that can take months or years to heal completely. About 40% of all bites are accompanied by more severe symptoms: fever , chills, edema , nausea, vomiting, dizziness, muscle and joint pain, and a measles-like rash. The bite becomes hard and inflamed, and may turn gangrenous. In most cases, fortunately, the bite simply produces a hard, painful, itchy, and discolored area that heals without treatment in two to three days.

BEES AND WASPS. The familiar symptoms of bee and wasp stings include pain, redness, swelling, and itchiness in the area of the sting. Multiple stings can have much more severe consequences. If an allergic reaction occurs, there can be life-threatening symptoms of facial swelling, throat closure, tongue swelling, and airway blockage within a very short time.

Snakes

Many pit viper and coral snake bites (20–60%) fail to poison (envenom) their victims, or manage to introduce only a small amount of venom into the victim's body. The wounds , however, can still become infected by the harmful microorganisms that snakes carry in their mouths.

Venomous pit viper bites usually begin to swell within 10 minutes and are sometimes painful. Other symptoms include edema at the wound site, skin blisters, discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Symptoms of severe poisoning include tingling in the scalp, fingers, and toes, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure , vomiting of blood, and coma .

Coral snake bites are painful but may be hard to see. After some time has passed, a bitten person begins to experience the effects of the venom, which include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Nerves in the head and neck can become paralyzed for six to 14 days, causing double vision, difficulty swallowing and speaking, respiratory failure , and other problems. Six to eight weeks may be needed before normal muscular strength is regained.

Marine animals

JELLYFISH. Jellyfish venom is delivered by barbs called nematocysts that are located on the creature's tentacles. They sting anyone who brushes up against them, causing a red lesion that is instantly painful and itchy. The pain can continue up to 48 hours. Severe cases may lead to necrosis, muscle spasms and cramps, vomiting, nausea, diarrhea , headaches, excessive sweating, and other symptoms. In rare instances, cardiorespiratory failure results.

STINGRAYS. Stingrays carry their venom in their tail spines, which can inflict deep puncture wounds. If, as often happens, pieces of spine become embedded in the wound, an infection can result. Most people are injured by a stingray when they inadvertently step on one that's resting, and are lashed in the ankle by its tail. Stingray venom produces immediate, excruciating pain that lasts several hours. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhage, a drop in blood pressure, and cardiac arrhythmia.

Diagnosis

Mammals

DOGS. Gathering information on the circumstances of a dog attack is a crucial part of bite treatment. Among other things, medical professionals need to know when the attack occurred (the chances of infection increase dramatically if the wound has been left untreated more than eight hours) and what led to the attack (unprovoked attacks are more likely to be associated with rabid animals). The patient's general health must also be assessed, including tetanus immunization history and possible allergies to medication.

A physical examination demands careful scrutiny of the wound, with special attention to possible bone, joint, ligament, muscle, tendon, nerve, or blood-vessel damage that may have been caused by deep punctures or severe crush injuries. Experts advise that serious hand injuries should be evaluated by a surgeon who specializes in such cases. Most of the time, laboratory tests to identify the microorganisms in bite wounds are ordered only if infection is present. X rays and other diagnostic procedures may also be necessary.

CATS. The diagnostic procedures used for dog bites also apply to cat bites.

HUMANS. Anyone who has received a human bite must be tested for hepatitis B and other diseases; ideally, the biter should be tested as well. Clenched-fist injuries require evaluation by a hand surgeon. Because many people will deny having been in a fight, medical professionals are advised to always consider lacerations over the fourth and fifth knuckle—a typical clenched-fist injury—to be evidence of a bite wound, no matter what an individual says. Medical professionals should also look for other indications of spousal or child abuse when evaluating human bites.

Arthropods

SPIDERS. Spider bites always require medical attention, although victims are often not aware that they've been bitten. To make matters worse, unless the spider is seen biting the victim, identifying which species is responsible is difficult. If possible, the spider should be captured and taken to the emergency room or doctor's office for identification.

Snakes

Diagnosis relies on a physical examination of the victim, information about the circumstances of the bite, and a look at the snake itself (if it can safely be brought in for identification). Blood tests and urinalysis supply important data on the victim's condition. Chest x rays and EKG (electrocardiogram) may also be necessary.

Treatment

Mammals

DOGS. Minor dog bites can be treated at home. The American Academy of Family Physicians recommends gently washing the wound with soap and water and then applying pressure to the injured area with a clean towel to stop the bleeding. Next, apply antibiotic ointment and a sterile bandage to the wound. To reduce swelling and fend off infection, ice should be applied and the injured area kept elevated above the level of the heart. The wound should be cleaned and ointment reapplied twice a day until healing is complete.

Any dog bite that does not stop bleeding after 15 minutes of pressure must be seen by a medical professional. The same is true for bites that are deep or gaping; for bites to the head, hands, or feet; and for bites that may have broken a bone, damaged nerves, or caused a major injury of another kind. Bite victims must also watch for signs of infection: fever, redness, swelling, warmth, increased tenderness, and pus at the wound site. Diabetics, people with AIDS or cancer , individuals who have not had a tetanus shot in five years, and anyone else who has a medical problem that can increase susceptibility to infection should seek medical treatment no matter how minor the bite appears.

Medical treatment of dog bites involves washing the wound with an anti-infective solution. Dead and/or damaged tissue may be need to be removed, and any person whose tetanus shots are not up to date should receive a booster. Some wounds are left open and allowed to heal on their own, from the inside out, while others require stitches (stitching may be delayed a few days if infection is a concern). Many emergency departments prescribe antibiotics for all people with dog bites, but some researchers suggest that antibiotics are usually unnecessary and should be limited to those whose injuries or other health problems make them likely candidates for infection. A follow-up visit after one or two days is generally required for anyone who has received bite treatment.

Other than death by trauma, the biggest threat from a dog bite is rabies (although no one in the United States has contracted rabies from a dog bite for many years). Dogs who bite people should be contained and tested for rabies, unless the owner can prove the animal has been immunized. If this is not possible, a rabies vaccine series for the victim is effective if administered within two days of the bite.

CATS. Because of the high risk of infection, people who are bitten by a cat should always see a doctor. Cat scratches do not require professional medical treatment unless the wound appears infected or the victim has a weakened immune system . Cats, like dogs, can also transmit rabies, and cats that inflict a bite should be contained and tested for rabies, unless their immunization history is known.

Medical treatment for cat bites generally follows the procedures used for dog bites. Experts advise, however, that cat-bite wounds should always be left open (not stitched) to prevent infection. Persons bitten by cats are also more likely to receive antibiotics as a preventive measure.

HUMANS. Human bites should always be examined by a doctor. Such bites are usually treated with antibiotics and left open because of the high risk of infection. A person who has been bitten may also require immunization against hepatitis B and other diseases. A follow-up visit is required after an occlusional bite. Persons who are being treated for a clenched-fist injury will require a daily follow-up examination for three to five days.

Arthropods

SPIDERS. Brown recluse spider bites require immediate medical attention. Put an antiseptic on the bite, apply ice to reduce swelling, then get the patient to a doctor as quickly as possible. Analgesics , antihistamines , and a tetanus shot are the standard course of treatment, along with erythromycin and other antibiotics to combat infection. If necrosis results, the affected areas may need debridement.

Experimental treatment includes steroids to combat the hemolysis that can result from the spider venom. Surgical excision of the bite once eschar has developed may be an effective way to remove the venom and prevent further tissue damage. Interestingly, the leprosy drug dapsone has shown some promise in this area, and may prevent the need for surgery. Hyperbaric oxygen treatments may also restore blood flow to dying tissue. A

promising antivenin has been developed, but it's not yet available for clinical use.

Black widow spider bites also need a doctor's care. Apply ice to the bite, then take the patient to an emergency room. If necessary, antivenin is administered. In less severe cases, the symptoms are treated with calcium and muscle relaxants for spasms, along with drugs to lower blood pressure.

BEES AND WASPS. Most stings can be treated at home. A stinger can be scraped off the skin with a razor blade, fingernail, credit card, or piece of paper; using tweezers may push more venom out of the venom sac and into the wound. The area should be cleaned and covered with an ice pack. Aspirin and other pain medications, oral antihistamines, and calamine lotion can relieve the pain, itching, and swelling.

The biggest risk from a bee sting is anaphylactic reaction to bee or wasp venom. This requires immediate medical attention. The danger signs, which usually begin within minutes after a sting, (but may not appear for several hours) include nausea, chest pain, hives (both internal and external), abdominal cramps, diarrhea, and difficulty swallowing or breathing. These last symptoms can be life threatening if not treated immediately. Patients with a history of allergic response to stings are prescribed a self-injecting kit of adrenaline and anti-histamine.

Snakes

Although most snakes are not venomous, any snakebite should immediately be examined at a hospital. While waiting for emergency help to arrive, the victim should wash the wound site with soap and water, and then keep the injured area still and at a level lower

than the heart. Ice should never be used on the wound, and no attempts should be made to extract the venom. Making a cut at the wound site is also dangerous. It is important to stay calm and wait for emergency medical aid.

When a snakebite victim arrives at a hospital, the medical staff must determine, if they can, whether the bite was inflicted by a venomous snake and, if so, how much venom the person received. Careful monitoring helps resolve doubtful cases. Fortunately, the effects of some snakebites can be counteracted with antivenin. Minor rattlesnake envenomations can be successfully treated without antivenin, as can copperhead and water moccasin bites. However, coral snake and the more dangerous rattlesnake envenomations require antivenin. Other treatment measures include antibiotics to prevent infection and a tetanus booster injection.

Marine animals

JELLYFISH. To stop envenomation from tentacles that cling to skin, various substances should be applied, depending on the species that delivered the sting. Vinegar, baking soda, meat tenderizer (papain), and other substances will neutralize nematocysts. Applying the wrong substance, however, can cause the nematocysts to fire again, increasing the dose of venom and the degree of pain for the victim. Once the tentacles have been neutralized, they can be scraped off, saved, and given to medical personnel for identification and diagnosis. Ice, topical anesthetics, antihistamines, steroids, and a tetanus booster can prevent further complications. As with bee stings, allergic reactions may occur, requiring emergency medical care.

STINGRAYS. Stingray wounds should be washed with salt water and then soaked in very hot water for 30–90 minutes to neutralize the venom. Afterwards, the wound should be examined by a doctor to ensure that no pieces of spine remain.

Alternative treatment

Arthropods

Several alternative self-care approaches are used to treat bee, wasp, and other minor arthropod stings, including aromatherapy, ayurvedic medicine, flower remedies, herbs, homeopathy , and nutritional therapy. The efficacy of these treatments has not been proven, however, and if alternative therapy delays the administration of traditional medical attention for dangerous bites or stings the risk of severe consequences increases.

Prognosis

Mammals

It is important to realize that apparently even minor bites can have serious consequences, and that prompt treatment is the key to a good outcome. Infected bites may require hospitalization and can be fatal if neglected. Surgery may be needed for severe bites.

Arthropods

SPIDERS. Even without treatment, adults tend to recover from black widow bites after two to three days. The risk of death, though rare, is highest for very young children, the elderly, and people with high blood pressure.

BEES AND WASPS. The pain and other symptoms of a bee or wasp sting normally fade after a few hours. People who are allergic to such stings, however, can experience a severe and occasionally fatal reaction.

Snakes

A snakebite victim's chances of survival are excellent if medical aid is rendered in time. Some bites, however, result in amputation, permanent deformity, or loss of function in the injured area.

Marine animals

STINGRAYS. Stingray venom only rarely kills its human victims.

Health care team roles

Persons trained in first aid provide initial support. Emergency medical technicians provide life support and transportation to medical facilities. Physicians trained in emergency or environmental medicine supervise treatment of bite victims. Registered nurses support, treat, and care for patients in emergency rooms and other hospital departments. Surgeons debride and repair serious bite wounds. Laboratory technicians process fluid and tissue specimens. Pathologists interpret test results. Physical therapists provide therapeutic services during the recovery period.

Prevention

Mammals

DOGS. The risk of a dog bite can be reduced by avoiding sick or stray dogs, staying away from dogfights (people often get bitten when they try to separate the animals), and not provoking or upsetting dogs while they are sleeping, eating, or tending their puppies. Infants and young children must never be left alone with a dog. Pit bulls, rottweilers, and German shepherd dogs—breeds that caused nearly half of all fatal dog attacks in the United States between 1997 and 2000—are potentially dangerous pets in households where children live or visit. All dog breeds benefit from obedience training and spaying or neutering to lessen the chances of aggressive behavior.

CATS. Warn children to stay away from strange cats and to avoid rough play and other behavior that can anger cats and cause them to bite.

Arthropods

SPIDERS. Common-sense precautions include exercising caution when clearing webs out of garages, outhouses, and other places favored by venomous spiders; keeping one's hands away from places where spiders may be lurking; and, when camping or vacationing, checking clothing, shoes, and sleeping areas.

BEES AND WASPS. When outdoors, avoid bee and wasp nests, and don't eat sweet food or wear bright clothing, perfumes, or fragranced cosmetics that attract bees and wasps.

Emergency medical kits containing self-injecting epinephrine to counter anaphylactic shock are available for people with a history of allergic response to insect stings; these should be carried with them at all times. People who suspect they are allergic should consult an allergist about immunotherapy shots that can build up resistance to bee and wasp venom.

Snakes

Mowing the lawn, trimming hedges, and removing brush from the yard discourages snakes from living close to homes. Use tongs to move brush, lumber, and firewood in case snakes are lying beneath them. Similarly, golfers should never use their hands to retrieve golf balls from a water hole, since snakes can be hiding in the rocks and weeds. Caution is also necessary when walking through weedy or grassy areas, and children should be prevented from playing in weedy, vacant lots and other places where snakes may live. Leather boots and long pants offer hikers and campers some protection from bites. Approaching a snake, even a dead one, can be dangerous, for recently killed snakes can still inflict a venomous bite if there is contact with the fangs.

Marine animals

JELLYFISH. Obey posted warning signs at the beach. Also, since jellyfish tentacles are transparent and can be up to 120 ft (36.5 m) long, great caution must be exercised whenever a jellyfish is sighted nearby.

STINGRAYS. Shuffling while walking through shallow areas that may be inhabited by stingrays will disturb the water, causing the animal to move before it can be stepped on.

Resources

BOOKS

Holve, Steve. "Envenomations." In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 2174-2178.

Linden, Christopher H., and Frederick H. Lovejoy, "Disorders Caused by Reptile Bites and Marine Animal Evenomations." In Harrison's Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2544-2548.

Norris, Robert L., Scott Oslund, and Paul S. Auerbach. "Ectoparasite Infestations and Arthropod Bites and Stings." In Harrison's Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2548-2554.

Sutherland, Struan, and James Tibballs. Australian Animal Toxins, 2nd ed. New York: Oxford University Press, 2001.

PERIODICALS

Graudins A., M. Padula, K. Broady, and G. M. Nicholson. "Red-back Spider (Latrodectus hasselti) Antivenom Prevents the Toxicity of Widow Spider Venoms. Annals of Emergency Medicine 37 no. 2 (2001): 154-160.

Herman, Bruce E., and Elisabeth Guenther Skokan. "Bites That Poison: A Tale of Spiders, Snakes, and Scorpions." Contemporary Pediatrics 16 no. 8 (1999): 41-65.

Jarvis, R. M., M. V. Neufeld, and C. T. Westfall. "Brown Recluse Spider Bite to the Eyelid." Ophthalmology 107, no. 8 (2000): 1492-1496.

Kasdan, M. L., A. S. Kasdan, and D. L. Hamilton. "Lionfish Envenomation." Plastic and Reconstructive Surgery 80, no. 4 (1987): 613-614.

Metry, D. W. and A.A. Hebert. "Insect and Arachnid Stings, Bites, Infestations, and Repellents." Pediatric Annals 29, no. 1 (2000): 39-48.

Sams, H. H., C.A. Dunnick, M. L. Smith, and L. E. King. "Necrotic Arachnidism. Journal of the American Academy of Dermatology 44, no. 4 (2001): 561-573.

Sams, H. H. "Nineteen Documented Cases of Loxosceles reclusa Envenomation." Journal of the American Academy of Dermatology 44, no. 4 (2001): 603-608.

ORGANIZATIONS

American Academy of Clinical Toxicology. 777 East Park Drive, PO Box 8820, Harrisburg, PA 17105-8820. (717) 558-7750. <http://www.clintox.org/index.html>.

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. <http://www.aaem.org>.

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 906-6000. <http://www.aafp.org>.

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 434-4000. <http://www.aap.org/default.htm>.

American Association of Poison Control Centers. 3201 New Mexico Avenue NW, Washington, DC 20016. (202) 362-7217. <http://www.aapcc.org>.

American College of Occupational and Environmental Medicine. 55 West Seegers Road, Arlington Heights, IL60005. (708) 228-6850. <http://www.acoem.org>.

OTHER

City of Phoenix, Arizona. "Bites and Stings." <http://www.ci.phoenix.az.us/FIRE/bitessna.html>.

Tamkin, Gary W. "Emergency Management of Brown Recluse Spider Bites: A Review." <http://www.highway60.com/mark/brs/tamkin.txt>.

University of Sydney, Australia. "Australian Spider and Insect Bites." <http://www.usyd.edu.au/su/anaes/spiders.html>.

L. Fleming Fallon, Jr., M.D., Ph.D.

KEY TERMS

Antibiotics —Substances used to fight bacteria that cause infection.

Antibodies —Substances in the blood created by the body to combat infection.

Antihistamines —Drugs that treat allergic reactions by acting against a substance called histamine, which the body releases as part of its immune response.

Antivenin —An antitoxin to a specific animal venom. Antivenin is extracted from the blood serum of horses (or other animals) that have been immunized against the toxin.

Blood serum —The component of blood plasma that remains after coagulation.

Debridement —Removal of dead and/or damaged tissue.

Edema —Excessive fluid buildup in a body tissue.

Eschar —Sloughed off dead tissue.

Hemolysis —Breakdown of red blood cells.

Necrosis —Dead skin, muscle, bone, or other tissue in the body caused by insufficient blood flow.

Pus —A thick yellowish or greenish fluid composed of the remains of dead white blood cells, pathogens, and decomposed cellular debris; a definite sign of infection.

Sepsis —A serious systemic infection caused by bacteria that have entered the bloodstream through a wound.

Bites and Stings

Definition

People can be injured by the bites or stings of many animals, including mammals such as dogs, cats, and fellow humans; arthropods such as spiders, bees, and wasps; snakes; and marine animals such as jellyfish and stingrays.

Description

Mammals

DOGS. In the United States, where the dog population exceeds 50 million, dogs surpass all other mammals in the number of bites inflicted on humans. Most come from family pets or other dogs known to the victim. Fortunately, most dog-bite injuries are minor. A 1994 telephone survey of American households indicated that there were 3,737,000 dog bites that did not require medical attention in the United States during that year, and 757,000 that did. Men and boys are more likely to be bitten than girls or women; not surprisingly, children face a greater risk than adults. Each year, about 10-20 Americans, mostly children under 10 years of age, are killed by dogs.

In the United States, dog bites send an estimated 340,000 people to the emergency room each year. Children under 10 are more likely than older people to need immediate medical treatment; this is especially true for boys between five and nine. Children under ten were also much more likely to be bitten on the face, neck, and head. Few of the injuries suffered by people seeking emergency treatment were serious; most patients were treated and released without being admitted or referred to another facility.

CATS. Although cats are found in nearly a third of American households, their bites are far less common than dog bites. According to one study, cats inflict perhaps 400,000 harmful bites in the United States each year. Cat bites typically cause less tissue damage, but they carry a higher risk of infection (30-40%) than dog bites (15-20%). Young girls are the most likely to be bitten by cats.

HUMANS. There are approximately 70,000 human bites each year in the United States. They can be just as serious a medical problem as a bite from an animal. Because the human mouth contains a multitude of potentially harmful microorganisms, these tend to become have a higher infection rate than those inflicted by animals.

Arthropods

Arthropods are invertebrates such as insects, arachnids, crustaceans, and other subgroups of the phylum Arthropoda—a group that encompasses more than 700,000 species. The list of arthropods that bite or sting is extensive and includes lice, bedbugs, fleas, mosquitoes, blackflies, ants, chiggers, ticks, centipedes, scorpions, and other creatures. Spiders, bees, and wasps are the three that people encounter most often.

SPIDERS. In the United States, only two kinds of venomous spider have a truly life-threatening bite: black widow spiders and brown recluse spiders. The black widow, which is found in every state but Alaska, is probably the most infamous widow spider. It prefers dark, dry places such as barns, garages, and outhouses, and also lives under rocks and logs. Disturbing a female black widow or her web may provoke a bite. Red widow spiders are far more rare, but can be found in parts of Florida; their sting is also quite venomous. Brown recluse spiders also prefer sheltered places, including clothing, and may bite if disturbed.

BEES AND WASPS. Bees and wasps will sting to defend their nests or if they are disturbed. Species common to the United States include honeybees, bumblebees, yellow jackets, bald-faced hornets, brown hornets, and paper wasps. More than 50 Americans die each year after being stung by a bee, wasp, or fire ant. Almost all of those deaths are caused by allergic reactions to the venom, not by its toxicity.

Snakes

There are 20 species of venomous snakes in the United States; they're found in every state except Maine, Alaska, and Hawaii. Each year about 8,000 Americans receive a venomous snakebite, but no more than about 15 die; most of the deaths are from rattlesnake bites.

The venomous snakes of the United States are divided into two families: Crotalidae (pit vipers) and Elapidae. Pit vipers, which take their name from the small heat-sensing pit that lies between each eye and nostril, are responsible for about 99% of the venomous snakebites suffered by Americans. The group includes rattlesnakes, copperheads, and cottonmouths (also called water moccasins). This type of snake delivers its venom through two long, hinged fangs in the upper jaw. Some pit vipers carry a potent, fast-acting venom that can damage the brain and spinal cord. The venom of others, such as the copperheads, is less harmful.

The Elapidae include two kinds of venomous coral snakes indigenous to the southern and western states. Because coral snakes are bashful creatures that come out only at night, they almost never bite humans, and are responsible for only about 25 bites a year in the United States. Coral snakes also have short fangs and a small mouth, which lessens the risk of a bite actually forcing venom through the skin and subcutaneous tissues into muscles or veins. However, if ingested, their venom is quite poisonous.

Marine animals

Several varieties of marine animal bite or sting, including sharks, jellyfish, stingrays, anemones, and even a few types of coral. Although only a few have venom powerful enough to kill, they can inflict painful injuries. As with spider and bee stings, allergic individuals can also have anaphylactic reactions to these bites.

Causes and symptoms

Mammals

DOGS. A typical dog bite results in a laceration, puncture, or crush injury. Infected bites usually cause pain, cellulitis (inflammation of the connective tissues), and a pus-filled discharge at the wound site within 8-24 hours. Most infections are confined to the wound site, but microorganisms in dogs' mouths can cause systemic and possibly life-threatening infections such as sepsis and meningitis, especially among people with compromised immune systems that decrease their resistance to infection. Rabies is rare among pet dogs in the United States, most of which have been vaccinated against the disease. Tetanus is also a rare complication.

CATS. Cat scratches and bites can transmit the Bartonella henselae bacterium, which can lead to cat-scratch disease, an uncommon and unpleasant but not usually life-threatening illness. The mouths of cats and dogs contain many of the same microorganisms, and many of the same types of infections can result.

Cat bites are mostly found on the arms and hands. Sharp cat teeth typically leave behind a deep puncture wound that can reach muscles, tendons, and bones, which are vulnerable to infection because of their comparatively poor blood supply. This is one reason why cat bites are much more likely than dog bites to become infected. People are also less inclined to give cat bites immediate medical attention, increasing the risk that infection will set in. Infected cat scratches on fingers or toes, in fact, have been known to spread inward to the bone, and result in the need for amputation of the digit.

HUMANS. Although children often bite other children, these bites are hardly ever severe. Most humans bites that require medical attention result from fights (raising the possibility of domestic or child abuse ), sexual activity, medical and dental treatment, and seizures. They can transmit a wide range of dangerous diseases, including hepatitis B, syphilis, tuberculosis, and HIV.

Human bites fall into two categories: occlusional (true) bites and clenched-fist injuries. The former present a low risk of infection. The latter, which are very infectious and can permanently damage the hand, usually result when a fist hits teeth during a fight. People often wait before seeking treatment for a clenched-fist injury, with the result that about half of such injuries are infected by the time they are seen by a medical professional.

Arthropods

SPIDERS. People do not always feel a black widow's bite. The first (and possibly only) evidence that a person has been bitten may be a mild swelling of the injured area and two red puncture marks showing where the spider's fangs entered the skin. Within a short time, however, some victims begin to experience severe muscle cramps and rigid abdominal muscles. Other possible symptoms include excessive sweating, nausea, vomiting, headaches, and vertigo as well as breathing, vision, and speech problems.

A brown recluse spider's bite can lead to necrotic arachnidism, in which the tissue in an area of up to several inches around the bite becomes necrotic, producing an open sore that can take months or years to heal completely. About 40% of all bites are accompanied by more severe symptoms: fever, chills, edema, nausea, vomiting, dizziness, muscle and joint pain, and a measles-like rash. The bite becomes hard and inflamed, and may turn gangrenous. In most cases, fortunately, the bite simply produces a hard, painful, itchy, and discolored area that heals without treatment in two to three days.

BEES AND WASPS. The familiar symptoms of bee and wasp stings include pain, redness, swelling, and itchiness in the area of the sting. Multiple stings can have much more severe consequences. If an allergic reaction occurs, there can be life-threatening symptoms of facial swelling, throat closure, tongue swelling, and airway blockage within a very short time.

Snakes

Many pit viper and coral snake bites (20-60%) fail to poison (envenom) their victims, or manage to introduce only a small amount of venom into the victim's body. The wounds, however, can still become infected by the harmful microorganisms that snakes carry in their mouths.

Venomous pit viper bites usually begin to swell within 10 minutes and are sometimes painful. Other symptoms include edema at the wound site, skin blisters, discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Symptoms of severe poisoning include tingling in the scalp, fingers, and toes, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure, vomiting of blood, and coma.

Coral snake bites are painful but may be hard to see. After some time has passed, a bitten person begins to experience the effects of the venom, which include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Nerves in the head and neck can become paralyzed for six to 14 days, causing double vision, difficulty swallowing and speaking, respiratory failure, and other problems. Six to eight weeks may be needed before normal muscular strength is regained.

Marine animals

JELLYFISH. Jellyfish venom is delivered by barbs called nematocysts that are located on the creature's tentacles. They sting anyone who brushes up against them, causing a red lesion that is instantly painful and itchy. The pain can continue up to 48 hours. Severe cases may lead to necrosis, muscle spasms and cramps, vomiting, nausea, diarrhea, headaches, excessive sweating, and other symptoms. In rare instances, cardiorespiratory failure results.

STINGRAYS. Stingrays carry their venom in their tail spines, which can inflict deep puncture wounds. If, as often happens, pieces of spine become embedded in the wound, an infection can result. Most people are injured by a stingray when they inadvertently step on one that's resting, and are lashed in the ankle by its tail. Stingray venom produces immediate, excruciating pain that lasts several hours. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhage, a drop in blood pressure, and cardiac arrhythmia.

Diagnosis

Mammals

DOGS. Gathering information on the circumstances of a dog attack is a crucial part of bite treatment. Among other things, medical professionals need to know when the attack occurred (the chances of infection increase dramatically if the wound has been left untreated more than eight hours) and what led to the attack (unprovoked attacks are more likely to be associated with rabid animals). The patient's general health must also be assessed, including tetanus immunization history and possible allergies to medication.

A physical examination demands careful scrutiny of the wound, with special attention to possible bone, joint, ligament, muscle, tendon, nerve, or blood-vessel damage that may have been caused by deep punctures or severe crush injuries. Experts advise that serious hand injuries should be evaluated by a surgeon who specializes in such cases. Most of the time, laboratory tests to identify the microorganisms in bite wounds are ordered only if infection is present. X rays and other diagnostic procedures may also be necessary.

CATS. The diagnostic procedures used for dog bites also apply to cat bites.

HUMANS. Anyone who has received a human bite must be tested for hepatitis B and other diseases; ideally, the biter should be tested as well. Clenched-fist injuries require evaluation by a hand surgeon. Because many people will deny having been in a fight, medical professionals are advised to always consider lacerations over the fourth and fifth knuckle—a typical clenched-fist injury—to be evidence of a bite wound, no matter what an individual says. Medical professionals should also look for other indications of spousal or child abuse when evaluating human bites.

Arthropods

SPIDERS. Spider bites always require medical attention, although victims are often not aware that they've been bitten. To make matters worse, unless the spider is seen biting the victim, identifying which species is responsible is difficult. If possible, the spider should be captured and taken to the emergency room or doctor's office for identification.

Snakes

Diagnosis relies on a physical examination of the victim, information about the circumstances of the bite, and a look at the snake itself (if it can safely be brought in for identification). Blood tests and urinalysis supply important data on the victim's condition. Chest x rays and EKG (electrocardiogram) may also be necessary.

Treatment

Mammals

DOGS. Minor dog bites can be treated at home. The American Academy of Family Physicians recommends gently washing the wound with soap and water and then applying pressure to the injured area with a clean towel to stop the bleeding. Next, apply antibiotic ointment and a sterile bandage to the wound. To reduce swelling and fend off infection, ice should be applied and the injured area kept elevated above the level of the heart. The wound should be cleaned and ointment reapplied twice a day until healing is complete.

Any dog bite that does not stop bleeding after 15 minutes of pressure must be seen by a medical professional. The same is true for bites that are deep or gaping; for bites to the head, hands, or feet; and for bites that may have broken a bone, damaged nerves, or caused a major injury of another kind. Bite victims must also watch for signs of infection: fever, redness, swelling, warmth, increased tenderness, and pus at the wound site. Diabetics, people with AIDS or cancer, individuals who have not had a tetanus shot in five years, and anyone else who has a medical problem that can increase susceptibility to infection should seek medical treatment no matter how minor the bite appears.

Medical treatment of dog bites involves washing the wound with an anti-infective solution. Dead and/or damaged tissue may be need to be removed, and any person whose tetanus shots are not up to date should receive a booster. Some wounds are left open and allowed to heal on their own, from the inside out, while others require stitches (stitching may be delayed a few days if infection is a concern). Many emergency departments prescribe antibiotics for all people with dog bites, but some researchers suggest that antibiotics are usually unnecessary and should be limited to those whose injuries or other health problems make them likely candidates for infection. A follow-up visit after one or two days is generally required for anyone who has received bite treatment.

Other than death by trauma, the biggest threat from a dog bite is rabies (although no one in the United States has contracted rabies from a dog bite for many years). Dogs who bite people should be contained and tested for rabies, unless the owner can prove the animal has been immunized. If this is not possible, a rabies vaccine series for the victim is effective if administered within two days of the bite.

CATS. Because of the high risk of infection, people who are bitten by a cat should always see a doctor. Cat scratches do not require professional medical treatment unless the wound appears infected or the victim has a weakened immune system. Cats, like dogs, can also transmit rabies, and cats that inflict a bite should be contained and tested for rabies, unless their immunization history is known.

Medical treatment for cat bites generally follows the procedures used for dog bites. Experts advise, however, that cat-bite wounds should always be left open (not stitched) to prevent infection. Persons bitten by cats are also more likely to receive antibiotics as a preventive measure.

HUMANS. Human bites should always be examined by a doctor. Such bites are usually treated with antibiotics and left open because of the high risk of infection. A person who has been bitten may also require immunization against hepatitis B and other diseases. A follow-up visit is required after an occlusional bite. Persons who are being treated for a clenched-fist injury will require a daily follow-up examination for three to five days.

Arthropods

SPIDERS. Brown recluse spider bites require immediate medical attention. Put an antiseptic on the bite, apply ice to reduce swelling, then get the patient to a doctor as quickly as possible. Analgesics, antihistamines, and a tetanus shot are the standard course of treatment, along with erythromycin and other antibiotics to combat infection. If necrosis results, the affected areas may need debridement.

Experimental treatment includes steroids to combat the hemolysis that can result from the spider venom. Surgical excision of the bite once eschar has developed may be an effective way to remove the venom and prevent further tissue damage. Interestingly, the leprosy drug dapsone has shown some promise in this area, and may prevent the need for surgery. Hyperbaric oxygen treatments may also restore blood flow to dying tissue. A promising antivenin has been developed, but it's not yet available for clinical use.

Black widow spider bites also need a doctor's care. Apply ice to the bite, then take the patient to an emergency room. If necessary, antivenin is administered. In less severe cases, the symptoms are treated with calcium and muscle relaxants for spasms, along with drugs to lower blood pressure.

BEES AND WASPS. Most stings can be treated at home. A stinger can be scraped off the skin with a razor blade, fingernail, credit card, or piece of paper; using tweezers may push more venom out of the venom sac and into the wound. The area should be cleaned and covered with an ice pack. Aspirin and other pain medications, oral antihistamines, and calamine lotion can relieve the pain, itching, and swelling.

The biggest risk from a bee sting is anaphylactic reaction to bee or wasp venom. This requires immediate medical attention. The danger signs, which usually begin within minutes after a sting, (but may not appear for several hours) include nausea, chest pain, hives (both internal and external), abdominal cramps, diarrhea, and difficulty swallowing or breathing. These last symptoms can be life threatening if not treated immediately. Patients with a history of allergic response to stings are prescribed a self-injecting kit of adrenaline and antihistamine.

Snakes

Although most snakes are not venomous, any snakebite should immediately be examined at a hospital. While waiting for emergency help to arrive, the victim should wash the wound site with soap and water, and then keep the injured area still and at a level lower than the heart. Ice should never be used on the wound, and no attempts should be made to extract the venom. Making a cut at the wound site is also dangerous. It is important to stay calm and wait for emergency medical aid.

When a snakebite victim arrives at a hospital, the medical staff must determine, if they can, whether the bite was inflicted by a venomous snake and, if so, how much venom the person received. Careful monitoring helps resolve doubtful cases. Fortunately, the effects of some snakebites can be counteracted with antivenin. Minor rattlesnake envenomations can be successfully treated without antivenin, as can copperhead and water moccasin bites. However, coral snake and the more dangerous rattlesnake envenomations require antivenin. Other treatment measures include antibiotics to prevent infection and a tetanus booster injection.

Marine animals

JELLYFISH. To stop envenomation from tentacles that cling to skin, various substances should be applied, depending on the species that delivered the sting. Vinegar, baking soda, meat tenderizer (papain), and other substances will neutralize nematocysts. Applying the wrong substance, however, can cause the nematocysts to fire again, increasing the dose of venom and the degree of pain for the victim. Once the tentacles have been neutralized, they can be scraped off, saved, and given to medical personnel for identification and diagnosis. Ice, topical anesthetics, antihistamines, steroids, and a tetanus booster can prevent further complications. As with bee stings, allergic reactions may occur, requiring emergency medical care.

STINGRAYS. Stingray wounds should be washed with salt water and then soaked in very hot water for 30-90 minutes to neutralize the venom. Afterwards, the wound should be examined by a doctor to ensure that no pieces of spine remain.

Alternative treatment

Arthropods

Several alternative self-care approaches are used to treat bee, wasp, and other minor arthropod stings, including aromatherapy, ayurvedic medicine, flower remedies, herbs, homeopathy, and nutritional therapy. The efficacy of these treatments has not been proven, however, and if alternative therapy delays the administration of traditional medical attention for dangerous bites or stings the risk of severe consequences increases.

Prognosis

Mammals

It is important to realize that apparently even minor bites can have serious consequences, and that prompt treatment is the key to a good outcome. Infected bites may require hospitalization and can be fatal if neglected. Surgery may be needed for severe bites.

Arthropods

SPIDERS. Even without treatment, adults tend to recover from black widow bites after two to three days. The risk of death, though rare, is highest for very young children, the elderly, and people with high blood pressure.

BEES AND WASPS. The pain and other symptoms of a bee or wasp sting normally fade after a few hours. People who are allergic to such stings, however, can experience a severe and occasionally fatal reaction.

Snakes

A snakebite victim's chances of survival are excellent if medical aid is rendered in time. Some bites, however, result in amputation, permanent deformity, or loss of function in the injured area.

Marine animals

STINGRAYS. Stingray venom only rarely kills its human victims.

Health care team roles

Persons trained in first aid provide initial support. Emergency medical technicians provide life support and transportation to medical facilities. Physicians trained in emergency or environmental medicine supervise treatment of bite victims. Registered nurses support, treat, and care for patients in emergency rooms and other hospital departments. Surgeons debride and repair serious bite wounds. Laboratory technicians process fluid and tissue specimens. Pathologists interpret test results. Physical therapists provide therapeutic services during the recovery period.

Prevention

Mammals

DOGS. The risk of a dog bite can be reduced by avoiding sick or stray dogs, staying away from dog-fights (people often get bitten when they try to separate the animals), and not provoking or upsetting dogs while they are sleeping, eating, or tending their puppies. Infants and young children must never be left alone with a dog. Pit bulls, rottweilers, and German shepherd dogs—breeds that caused nearly half of all fatal dog attacks in the United States between 1997 and 2000—are potentially dangerous pets in households where children live or visit. All dog breeds benefit from obedience training and spaying or neutering to lessen the chances of aggressive behavior.

CATS. Warn children to stay away from strange cats and to avoid rough play and other behavior that can anger cats and cause them to bite.

Arthropods

SPIDERS. Common-sense precautions include exercising caution when clearing webs out of garages, outhouses, and other places favored by venomous spiders; keeping one's hands away from places where spiders may be lurking; and, when camping or vacationing, checking clothing, shoes, and sleeping areas.

BEES AND WASPS. When outdoors, avoid bee and wasp nests, and don't eat sweet food or wear bright clothing, perfumes, or fragranced cosmetics that attract bees and wasps.

Emergency medical kits containing self-injecting epinephrine to counter anaphylactic shock are available for people with a history of allergic response to insect stings; these should be carried with them at all times. People who suspect they are allergic should consult an allergist about immunotherapy shots that can build up resistance to bee and wasp venom.

Snakes

Mowing the lawn, trimming hedges, and removing brush from the yard discourages snakes from living close to homes. Use tongs to move brush, lumber, and firewood in case snakes are lying beneath them. Similarly, golfers should never use their hands to retrieve golf balls from a water hole, since snakes can be hiding in the rocks and weeds. Caution is also necessary when walking through weedy or grassy areas, and children should be prevented from playing in weedy, vacant lots and other places where snakes may live. Leather boots and long pants offer hikers and campers some protection from bites. Approaching a snake, even a dead one, can be dangerous, for recently killed snakes can still inflict a venomous bite if there is contact with the fangs.

Marine animals

JELLYFISH. Obey posted warning signs at the beach. Also, since jellyfish tentacles are transparent and can be up to 120 ft (36.5 m) long, great caution must be exercised whenever a jellyfish is sighted nearby.

STINGRAYS. Shuffling while walking through shallow areas that may be inhabited by stingrays will disturb the water, causing the animal to move before it can be stepped on.

KEY TERMS

Antibiotics— Substances used to fight bacteria that cause infection.

Antibodies— Substances in the blood created by the body to combat infection.

Antihistamines— Drugs that treat allergic reactions by acting against a substance called histamine, which the body releases as part of its immune response.

Antivenin— an antitoxin to a specific animal venom. Antivenin is extracted from the blood serum of horses (or other animals) that have been immunized against the toxin.

Blood serum— The component of blood plasma that remains after coagulation.

Debridement— Removal of dead and/or damaged tissue.

Edema— Excessive fluid buildup in a body tissue.

Eschar— Sloughed off dead tissue.

Hemolysis— Breakdown of red blood cells.

Necrosis— Dead skin, muscle, bone, or other tissue in the body caused by insufficient blood flow.

Pus— A thick yellowish or greenish fluid composed of the remains of dead white blood cells, pathogens, and decomposed cellular debris; a definite sign of infection.

Sepsis— A serious systemic infection caused by bacteria that have entered the bloodstream through a wound.

Resources

BOOKS

Holve, Steve. "Envenomations." In Cecil Textbook of Medicine, 21st ed., edited by Lee Goldman and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, 2174-2178.

Linden, Christopher H., and Frederick H. Lovejoy, "Disorders Caused by Reptile Bites and Marine Animal Evenomations." In Harrison's Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2544-2548.

Norris, Robert L., Scott Oslund, and Paul S. Auerbach. "Ectoparasite Infestations and Arthropod Bites and Stings." In Harrison's Principles of Internal Medicine, 14th ed., edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, 2548-2554.

Sutherland, Struan, and James Tibballs. Australian Animal Toxins, 2nd ed. New York: Oxford University Press, 2001.

PERIODICALS

Graudins A., M. Padula, K. Broady, and G. M. Nicholson. "Red-back Spider (Latrodectus hasselti) Antivenom Prevents the Toxicity of Widow Spider Venoms. Annals of Emergency Medicine 37 no. 2 (2001): 154-160.

Herman, Bruce E., and Elisabeth Guenther Skokan. "Bites That Poison: A Tale of Spiders, Snakes, and Scorpions." Contemporary Pediatrics 16 no. 8 (1999): 41-65.

Jarvis, R. M., M. V. Neufeld, and C. T. Westfall. "Brown Recluse Spider Bite to the Eyelid." Ophthalmology 107, no. 8 (2000): 1492-1496.

Kasdan, M. L., A. S. Kasdan, and D. L. Hamilton. "Lionfish Envenomation." Plastic and Reconstructive Surgery 80, no. 4 (1987): 613-614.

Metry, D. W. and A. A. Hebert. "Insect and Arachnid Stings, Bites, Infestations, and Repellents." Pediatric Annals 29, no. 1 (2000): 39-48.

Sams, H. H., C. A. Dunnick, M. L. Smith, and L. E. King. "Necrotic Arachnidism. Journal of the American Academy of Dermatology 44, no. 4 (2001): 561-573.

Sams, H. H. "Nineteen Documented Cases of Loxosceles reclusa Envenomation." Journal of the American Academy of Dermatology 44, no. 4 (2001): 603-608.

ORGANIZATIONS

American Academy of Clinical Toxicology. 777 East Park Drive, PO Box 8820, Harrisburg, PA 17105-8820. (717) 558-7750. 〈http://www.clintox.org/index.html〉.

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. 〈http://www.aaem.org〉.

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 906-6000. 〈http://www.aafp.org〉.

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 434-4000. 〈http://www.aap.org/default.htm〉.

American Association of Poison Control Centers. 3201 New Mexico Avenue NW, Washington, DC 20016. (202) 362-7217. 〈http://www.aapcc.org〉.

American College of Occupational and Environmental Medicine. 55 West Seegers Road, Arlington Heights, IL 60005. (708) 228-6850. 〈http://www.acoem.org〉.

OTHER

City of Phoenix, Arizona. "Bites and Stings." 〈http://www.ci.phoenix.az.us/FIRE/bitessna.html〉.

Tamkin, Gary W. "Emergency Management of Brown Recluse Spider Bites: A Review." 〈http://www.highway60.com/mark/brs/tamkin.txt〉.

University of Sydney, Australia. "Australian Spider and Insect Bites." 〈http://www.usyd.edu.au/su/anaes/spiders.html〉.

Bites and stings

Definition

Humans can be injured by the bites or stings of many kinds of insects and animals. These range from the bites from a neighbor's dog or cat to bites from fellow humans and spiders to the stings from bees, wasps, snakes, and marine animals such as jellyfish and stingrays.

Description

Mammals

DOGS With more than 60 million pet dogs in the United States, plus thousands of strays, it is not surprising that an estimated 4.7 million Americans a year are bitten by a dog. Although most dog-bite injuries are minor, about 400,000 children seek medical attention for a dog bite every year, according to the Centers for Disease Control and Prevention. Of those injured, about 386,000 require emergency treatment and about a dozen die from their injuries. However, most of the injuries suffered by children seeking treatment in emergency rooms are of low severity and result in treatment and quick release from the hospital.

Children aged five to nine are most likely to be injured by dog bites. Males are more likely than females to require emergency treatment. About two-thirds of injuries to children aged four years or younger are to the head and neck.

Studies also show that most dog bites are from pets or other dogs known to the child who is bitten. In fact, more than half of the bites seen by emergency departments occur at home. Many of the bites result from attempting to break up fights between animals.

CATS Although cats are found in nearly one third of U.S. households, cat bites are far less common than dog bites. According to one study, cats inflict perhaps 400,000 harmful bites in the United States each year. The tissue damage caused by cat bites is usually limited but carries a high risk of infection. Whereas the infection rate for dog bite injuries is 15 to 20 percent, the infection rate for cat bites is 30 to 40 percent. Cat bites are also more likely to be provoked. A typical person who has been bitten is a young girl playing with a pet.

HUMANS Bites from mammals other than dogs and cats are uncommon, with one exception—human bites. There are approximately 70,000 human bites each year in the United States. Because the human mouth contains a multitude of potentially harmful microorganisms, human bites are more infectious than those of most other mammals.

Arthropods

Arthropods are invertebrates belonging to the phylum Arthropoda, the jointed-leg, spineless creatures of the world. Arthropoda include insects, arachnids (spiders), crustaceans, and other subgroups. There are more than 700,000 species in all. The list of arthropods that bite or sting humans is extensive and includes lice, bedbugs, fleas, mosquitoes, black flies, ants, chiggers, ticks, centipedes, scorpions, and other species. Spiders, ants, bees, and wasps are the four kinds of arthropod that most often bite people.

SPIDERS In the United States, only two kinds of venomous spider are truly dangerous: black widow spiders and brown recluse (violin or fiddle) spiders. The black widow, which is found in every state but Alaska, prefers dark, dry places, such as barns, garages, and outhouses, and also lives under rocks and logs. Disturbing a female black widow or its web may provoke a bite. Brown recluse spiders also prefer sheltered places, including clothing, and may bite if disturbed.

ANTS, BEES, AND WASPS Ants, bees, and wasps will sting to defend their nests or if they are disturbed. Ants sting more than 9.3 million people each year. Other hymenoptera account for more than 1 million stings annually. Species common to the United States include fire ants, honeybees, bumblebees, yellow jackets, bald-faced hornets, brown hornets, and paper wasps. The Africanized bee species, also called "killer bees," is as of 2004 found in the United States.

More than 50 Americans die each year after being stung by a bee or wasp. Almost all of those deaths are the result of allergic reactions to the sting and not of exposure to the venom itself.

Snakes

There are 20 species of venomous snakes in the United States. These snakes are found in every state except Maine, Alaska, and Hawaii. Each year about 8,000 Americans receive a venomous snakebite, but no more than about 15 die, mostly from rattlesnake bites.

The venomous snakes of the United States are divided into two families: the Crotalidae (pit vipers) and the Elapidae. Pit vipers, named after the small heat-sensing pit that lies between each eye and nostril, are responsible for about 99 percent of the venomous snakebites suffered by Americans. Rattlesnakes, copperheads, and cottonmouths (also called water moccasins) are pit vipers. This family of snakes delivers its venom through two long, hinged fangs in the upper jaw. Some pit vipers carry potent venom that can threaten the brain and spinal cord. The venom of others, such as the copperhead, is less harmful.

The Elapidae family includes two kinds of venomous coral snakes indigenous to the southern and western states. Because coral snakes are creatures that come out only at night, they almost never bite humans; they are held responsible for approximately 25 bites a year in the United States. Coral snakes also have short fangs and a small mouth, which lowers the risk of a bite actually forcing venom into the human body. However, their venom is highly poisonous.

Marine animals

Several varieties of marine animal may bite or sting. Jellyfish and stingrays are two kinds that pose a threat to people who live or vacation in coastal communities.

Causes and symptoms

Mammals

DOGS A typical dog bite results in a laceration, tear, puncture, or crush injury. Bites from large, powerful dogs may even cause fractures and dangerous internal injuries. Also, dogs trained to attack may bite repeatedly during a single episode. Infected bites usually cause pain , inflammation of the connective tissues, and a pusfilled discharge at the wound site within eight to 24 hours. Most infections are confined to the wound site, but many of the microorganisms in the mouths of dogs can cause systemic and possibly life-threatening infections. Examples are bacteremia and meningitis , especially severe in children with health conditions that increase their susceptibility to infection. Rabies is rare among pet dogs in the United States, most of which have been vaccinated against the disease. Tetanus is also rare but can be transmitted by a dog bite if the victim is not immunized.

CATS The mouths of cats and dogs contain many of the same microorganisms. Cat scratches and bites are also capable of transmitting the Bartonella henselae bacterium, which can lead to cat-scratch disease , an unpleasant but usually not life-threatening illness.

Cat bites are mostly found on the arms and hands. Sharp cat teeth typically leave behind a deep puncture wound that can reach muscles, tendons, and bones, which are vulnerable to infection because of their comparatively poor blood supply. This is why cat bites are much more likely to become infected than dog bites. Also, people are less inclined to view cat bites as dangerous enough to require immediate attention. The risk that infection has set in by the time a medical professional is consulted is, therefore, greater.

HUMANS Humans bites result from fights, sexual activity, medical and dental treatment, and seizures. Bites also may be sign of child abuse . Children often bite other children, but those bites are hardly ever severe. Human bites are capable of transmitting a wide range of dangerous diseases, including hepatitis B , syphilis, and tuberculosis .

Human bites fall into two categories: occlusional bites and clenched-fist injuries. Occlusional bites result from an actual bite and present a lower risk of infection. The clenched-fist injury happens when a fist hits a mouth during a fight and may lead to an infected hand.

Arthropods

SPIDERS As a rule, children rarely see a black widow bite them, nor do they feel the bite when it happens. The first (and possibly only) evidence that a child has been bitten may be a mild swelling of the injured area and two red puncture marks. Within a short time, however, some victims begin to experience severe muscle cramps and rigidity of the abdominal muscles. Other possible symptoms include excessive sweating, nausea , vomiting , headaches, and vertigo, as well as breathing, vision, and speech problems.

A brown recluse spider's bite can lead to necrotic arachnidism, in which the tissue in an area of up to several inches around the bite becomes necrotic (dies), producing an open sore that can take months or years to disappear. In most cases, however, the bite simply produces a hard, painful, itchy, and discolored area that heals without treatment in two to three days. The bite may also be accompanied by fever , chills, edema (an accumulation of excess tissue fluid), nausea and vomiting , dizziness , muscle and joint pain, and a rash.

BEES, WASPS AND ANTS The familiar symptoms of bee, wasp, and ant stings include pain, redness, swelling, and itchiness in the area of the sting. Multiple stings can have much more severe consequences, such as anaphylaxis , a life-threatening allergic reaction that occurs in children who are hypersensitive to the venom.

The fire ant sting usually produces immediate pain followed by a red, swollen area that disappears within 45 minutes. A blister or a red, swollen, itchy patch then develops. The blister may rupture and become infected.

Snakes

Venomous pit viper bites usually begin to swell within ten minutes and sometimes are painful. Other symptoms include skin blisters and discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Severe poisoning can also lead to tingling in the scalp, fingers, and toes, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure, vomiting of blood, and coma.

Many pit viper and coral snake bites (20%) fail to poison their victim or introduce only a small amount of venom into the victim's body. The wounds , however, can still become infected by the harmful microorganisms that snakes carry in their mouths.

Coral snake bites are painful but may be hard to see. One to seven hours after the bite, the victim begins to experience the effects of the venom, which include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Major nerves of the body can become paralyzed for six to 14 days, causing double vision, difficulty swallowing and speaking, respiratory failure, and other problems. Six to eight weeks may be needed before normal muscular strength is regained.

Marine animals

JELLYFISH Jellyfish venom is delivered by barbs called nematocysts, which are located on the creature's tentacles and penetrate the skin of people who brush up against them. Instantly painful and itchy red lesions usually result. The pain can continue up to 48 hours. Severe cases may lead to skin necrosis, muscle spasms and cramps , vomiting, nausea, diarrhea , headaches, excessive sweating, and other symptoms. In rare instances, cardiorespiratory (heart/lung) failure may also occur.

STINGRAYS Tail spines are the delivery mechanism for stingray venom. Deep puncture wounds result that can cause an infection if pieces of spine become embedded in the wound. A typical stingray injury scenario involves a person who inadvertently steps on a resting stingray and is lashed in the ankle by its tail. Stingray venom produces immediate, excruciating pain that lasts several hours. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhage (bleeding), a drop in blood pressure, and cardiac arrhythmia (disordered heart beat).

Diagnosis

Mammals

DOGS Gathering information on the circumstances of a dog attack is a crucial part of treatment. Medical professionals need to know:

• when the attack occurred (The chances of infection increase dramatically if the wound has been left untreated for more than eight hours.)
• what led to the attack (Unprovoked attacks are more likely to be associated with rabies.)
• the child's general health, including tetanus immunization history and information about allergies to medication and pre-existing health problems that may increase the risk of infection

A physical examination requires careful scrutiny of the wound, with special attention to possible bone, joint, ligament, muscle, tendon, nerve, or blood-vessel damage caused by deep punctures or severe crush injuries. Serious hand injuries should be evaluated by a specialized surgeon. Most of the time, laboratory tests for identifying the microorganisms in bite wounds are performed if infection is present. X rays and other diagnostic procedures may also be necessary.

CATS The diagnostic procedures used for dog bites also apply to cat bites.

HUMAN Testing the blood of a person who has been bitten for immunity to hepatitis B and other diseases is always necessary after a human bite. Ideally, the biter should be tested as well for the presence of transmissible disease. Physicians can advise if this is necessary if the biter is another small child. Medical professionals will also look for indications of child abuse when evaluating human bites.

Arthropods

SPIDERS Because bites from widow spiders and brown spiders require different treatment, capturing and identifying the spider helps to establish diagnosis.

Snakes

Diagnosis relies on a physical examination of the victim, information about the circumstances of the bite, and a look at the snake itself (if it can safely be killed and brought in for identification). Blood tests and urinalysis supply important data on the victim's condition. Chest x rays and electrocardiography (a procedure for measuring heart activity) may also be necessary.

Treatment

Mammals

DOGS Minor dog bites can be treated at home. The American Academy of Family Physicians recommends gently washing the wound with soap and water and then applying pressure to the injured area with a clean towel to stop the bleeding. The next step is to apply antibiotic ointment and a sterile bandage to the wound. To reduce swelling and fend off infection, ice should be applied and the injured area kept elevated above the level of the heart. The wound should be cleaned and covered with ointment twice a day until it heals.

Any dog bite that does not stop bleeding after 15 minutes of pressure must be seen by a medical professional. The same is true for bites that are deep or gaping; for bites to the head, hands, or feet; and for bites that may have broken a bone, damaged nerves, or caused a major injury of another kind. Bite victims must also watch for infection. A fever is a sign of infection, as are redness, swelling, warmth, increased tenderness, and pus at the wound site. Children with diabetes or cancer who have not had a tetanus shot in five years or who have a medical problem that can increase susceptibility to infection should seek medical treatment no matter how minor the bite appears.

Medical treatment of dog bites involves washing the wound with an anti-infective solution. Removal of dead and damaged tissue (under local, regional, or general anesthetic) may be required after the wound has been washed, and any child whose tetanus shots are not up-to-date should receive a booster injection. Some wounds are left open and allowed to heal on their own, while others require stitches (stitching may be delayed a few days if infection is a concern). Many emergency departments prescribe antibiotics for all people with dog bites, but some researchers suggest that antibiotics are usually unnecessary and should be limited to those whose injuries or other health problems make them likely candidates for infection. A follow-up visit after one or two days is generally required for anyone who has received bite treatment.

CATS Because of the high risk of infection, parents of children who are bitten by a cat should always call the child's doctor. Most cat scratches do not require professional medical treatment unless the wound appears infected or the scratched person has a weakened immune system.

Medical treatment for cat bites generally follows the procedures used for dog bites. Experts advise, however, that cat-bite wounds should always be left open to prevent infection. Persons who have been bitten by cats generally receive antibiotics as a preventive measure.

HUMANS Human bites should always be examined by a doctor. Such bites are usually treated with antibiotics and left open because of the high risk of infection. A person who has been bitten may also require immunization against hepatitis B and other diseases. This is usually not necessary if the biter is a child.

Arthropods

SPIDERS No spider bite should be ignored. The antidote for severe widow spider bites is a substance called antivenin, which contains antibodies taken from the blood serum of horses injected with spider venom. Doctors exercise caution in using antivenin, however, because it can trigger anaphylactic shock, a potentially deadly (though treatable) allergic reaction, and serum sickness, an inflammatory response that can give rise to joint pain, a fever, rashes , and other unpleasant, though rarely serious, consequences.

An antivenin for brown spider bites exists as well, but it is not readily available in the United States. The drug dapsone, used to treat leprosy, can sometimes stop the tissue death associated with a brown spider bite. Necrotic areas (areas of dead tissue) may need debridement (removal of dead and damaged tissue) and skin grafts. Pain medications, antihistamines , antibiotics, and tetanus shots are a few of the other treatments that are sometimes necessary after a bite from a brown spider or widow spider.

BEES, WASPS, AND ANTS Most stings can be treated at home. A stinger that is stuck in the skin can be scraped off with a blade, fingernail, credit card, or piece of paper (using tweezers may push more venom out of the venom sac and into the wound). The area should be cleaned and covered with an ice pack. Aspirin and other pain medications, oral antihistamines, and calamine lotion are good for treating minor symptoms. Putting meat tenderizer on the wound has no effect.

Persons who have been stung and experience an allergic reaction or who are at risk due to their medical history require immediate medical attention. The danger signs, which usually begin ten minutes after an individual is stung (though possibly not for several hours) include nausea, faintness, chest pain, abdominal cramps, diarrhea, and difficulty swallowing or breathing.

Snakes

Although most snakes are not venomous, any snakebite should immediately be examined at a hospital. While waiting for emergency help to arrive, the victim should wash the wound site with soap and water and then keep the injured area still and at a level lower than the heart. Ice should never be used on the wound site nor should attempts be made to suck out the venom. Making a cut at the wound site is also dangerous. It is important to stay calm and wait for emergency medical aid if it can arrive quickly. Otherwise, the child should proceed directly to a hospital.

When the child arrives at a hospital, the medical staff must determine whether the bite was inflicted by a venomous snake and, if so, whether envenomation (venom is injected into the victim) occurred and how much venom the person has received. Patients may develop low blood pressure, abnormal blood clotting, or severe pain, all of which require aggressive treatment. Fortunately, the effects of some snake bites can be counteracted with antivenin. Minor rattlesnake envenomations can be successfully treated without antivenin, as can copperhead and watermoccasin bites. However, coral snake envenomations and the more dangerous rattlesnake envenomations require antivenin, sometimes in large amounts. Other treatment measures include antibiotics to prevent infection and a tetanus booster injection.

Marine animals

JELLYFISH Vinegar and other acidic substances are used to neutralize jellyfish nematocysts still clinging to the skin, which are then scraped off. Anesthetic ointments, antihistamine creams, and steroid lotions applied to the skin are sometimes beneficial. Other measures may be necessary to counter the many harmful effects of jellyfish stings, which, if severe, require emergency medical care.

STINGRAYS Stingray wounds should be washed with saltwater and then soaked in very hot water for 30 to 90 minutes to neutralize the venom. Afterwards, the wound should be examined by a doctor to ensure that no pieces of spine remain.

Prognosis

Mammals

Prompt treatment and recognizing that even apparently minor bites can have serious consequences are the keys to a good outcome after a mammal bite. Infected bites can be fatal if neglected. Surgery and hospitalization may be needed for severe bites.

Arthropods

SPIDERS Even without treatment, most children recover from black widow bites after two to three days. In the case of brown spider bites, the risk of death is greatest for children, though rare.

BEES, WASPS, AND ANTS The pain and other symptoms of a bee or wasp sting normally fade away after a few hours. Children who are allergic to such stings, however, can experience severe and occasionally fatal anaphylaxis (life-threatening allergic reaction to bites and stings).

Snakes

A snakebite victim's chances of survival are excellent if medical aid is obtained in time. Some bites, however, can result in amputation, permanent deformity, or loss of function in the injured area, although this is rare.

Marine animals

STINGRAYS Stingray venom kills its human victims on rare occasions.

Prevention

Mammals

DOGS The risk of a dog-bite injury can be reduced by avoiding sick or stray dogs, staying away from dogfights (children can get bitten when they try to separate the animals), and not behaving in ways that might provoke or upset dogs, such as wrestling with them or bothering them while they are sleeping, eating, or looking after their puppies. Infants and young children must never be left alone with a dog. Pit bulls, rottweilers, and German shepherds (responsible for nearly half of all fatal dog attacks in the United States in 2000) are potentially dangerous pets in households where children live or visit. For all breeds of dog, obedience training as well as spaying or neutering lessen the chances of aggressive behavior .

CATS Prevention involves warning children to stay away from strange cats and to avoid rough play and other behavior that can anger cats and cause them to bite.

Arthropods

SPIDERS Common-sense precautions include clearing webs out of garages, out buildings, and other places favored by venomous spiders; teaching children to keep their hands away from places where spiders may be lurking; and, when camping or vacationing, checking clothing, shoes, and sleeping areas.

BEES, WASPS, AND ANTS Children should avoid the nests of bees, wasps, and ants. When playing outside in an area where these insects are found, children also should avoid eating sweet food or wearing bright clothing, perfumes, or cosmetics that attract bees, wasps, and ants.

Emergency medical kits containing self-administrable epinephrine to counter anaphylactic shock are available for allergic children and should be carried by them at all times. Children who are suspected of being allergic should consult an allergist about shots that can reduce reactions to bee and wasp venom (venom immunotherapy). Venom immunotherapy in children leads to a significantly lower risk of reaction to stings up to ten to 20 years after treatment is stopped.

Snakes

Snakes should not be kept as pets. Measures such as mowing the lawn, keeping hedges trimmed, and removing brush from the yard also discourages snakes from living close to human dwellings. Tongs should be used to move brush, lumber, and firewood, to avoid exposing one's hands to snakes that might be lying underneath. Children should be prevented from playing in weedy, vacant lots and other places where snakes may live. Leather boots and long pants offer hikers and campers some protection from bites. Approaching a snake, even a dead one, can be dangerous since the venom of recently killed snakes may still be active.

Marine animals

JELLYFISH Prevention of jellyfish stings includes obeying posted warning signs at the beach. Also, jellyfish tentacles may be transparent and up to 120 feet (36.5 m) long; therefore, great caution must be exercised whenever a jellyfish is sighted nearby.

STINGRAYS Kicking the sand while walking through shallow areas that may be inhabited by stingrays will disturb the water, causing the animal to move before it can be stepped on.

Parental concerns

Children frequently play in areas where they can be exposed to stings and bites. Children who are sensitive to certain stings and bites are at risk for serious anaphylactic reactions.

KEY TERMS

Anaphylaxis —Also called anaphylactic shock; a severe allergic reaction characterized by airway constriction, tissue swelling, and lowered blood pressure.

Antibiotics —Drugs that are designed to kill or inhibit the growth of the bacteria that cause infections.

Antibody —A special protein made by the body's immune system as a defense against foreign material (bacteria, viruses, etc.) that enters the body. It is uniquely designed to attack and neutralize the specific antigen that triggered the immune response.

Antihistamine —A drug used to treat allergic conditions that blocks the effects of histamine, a substance in the body that causes itching, vascular changes, and mucus secretion when released by cells.

Arachnid —A large class of arthropods that includes spiders, scorpions, mites, and ticks.

Arachnidism —Poisoning resulting from the bite or sting of an arachnid.

Bacteremia —Bacterial infection of the blood.

Blood serum —A component of blood.

Immune system —The system of specialized organs, lymph nodes, and blood cells throughout the body that work together to defend the body against foreign invaders (bacteria, viruses, fungi, etc.).

Killer bees —Hybrids of African bees accidentally introduced into the wild in South and North America in 1956 and first reported in Texas in 1990. They were first imported by Brazilian scientists attempting to create a new hybrid bee to improve honey production.

Lymph nodes —Small, bean-shaped collections of tissue located throughout the lymphatic system. They produce cells and proteins that fight infection and filter lymph. Nodes are sometimes called lymph glands.

Pus —A thick, yellowish or greenish fluid composed of the remains of dead white blood cells, pathogens, and decomposed cellular debris. It is most often associated with bacterial infection.

See also Insect sting allergy.

Resources

BOOKS

Holve, Steve. "Envenomations." In Cecil Textbook of Medicine, 21st ed. Edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2174–78.

"Overview of the 2002 Household Pet Survey." In U.S. Pet Ownership and Demographics Sourcebook. Schaumburg, IL: American Veterinary Medical Association, 2002.

Nagami, Pamela. Bitten: True Medical Stories of Bites and Stings. London: St. Martin's Press, 2004.

Royston, Angela. Stings and Bites. Oxford, UK: Heinemann Library, 2004.

Siverstein, Alvin, et al. Bites and Stings. Danbury, CT: Scholastic Library Publishing, 2002.

PERIODICALS

Graudins, A., et al. "Red-back spider (Latrodectus hasselti) antivenom prevents the toxicity of widow spider venoms." Annals of Emergency Medicine 37 (2001): 154–60.

Jarvis, R. M., et al. "Brown recluse spider bite to the eyelid." Ophthalmology 107 (2000): 1492–96.

Metry, D. W., and A. A. Hebert. "Insect and arachnid stings, bites, infestations, and repellents." Pediatric Annals 29 (2000): 39–48.

Sams, H. H. "Nineteen documented cases of Loxosceles reclusa envenomation." Journal of the American Academy of Dermatology 44 (2001): 603–08.

Sams, H. H., et al. "Necrotic arachnidism." Journal of the American Academy of Dermatology 44 (2001): 561–73.

ORGANIZATIONS

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. Web site: <www.aaem.org>.

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211–2672. Web site: <www.aafp.org>.

American Medical Association. 515 N. State Street, Chicago, IL 60610. Web site: <www.ama-assn.org>.

Christine Kuehn Kelly

Bites and stings

Definition

A bite is an injury caused by an animal, such as a mammal or insect, that breaks the skin. A sting is a puncture wound made by insects or marine animals. There is often a danger of infection from toxins or venom with bites and stings.

Description

In the United States, dogs surpass all other mammals in the number of bites inflicted on humans. Children face a greater risk than adults, and children under 10 years old are more liable than anyone to suffer serious bites to the face, neck, and head. Cat bites are far less common than dog bites, but they carry a higher risk of infection. Bites from wild animals should be of especial concern due to the risk of rabies . More than 70,000 human-to-human bites a year are reported in the United States. Human bites are more infectious than those of any other animal.

The most common invertebrates responsible for bites and stings include lice, bedbugs, fleas, mosquitoes, black flies, fire ants, chiggers, ticks, centipedes, scorpions, spiders, bees, and wasps. Black widows and brown recluse spiders are the two most common poisonous spiders in the United States. The bites of most other spiders in North America cause only minor reactions. Ticks attach themselves to the skin and feed on the blood of animals. Most are relatively harmless, but some carry diseases such as Rocky Mountain spotted fever and Lyme disease . Now, people worry about the danger or West Nile virus from mosquito bites. Bees and wasps will sting to defend their nests or if they are disturbed. Fifty or more people a year die in the United States after being stung by bees, wasps, or fire ants. Almost all of those deaths are the result of allergic reactions.

The poisonous snakes of the United States are divided into two families, pit vipers (which include rattlesnakes, copperheads, and cottonmouths, also called water moccasins) and the coral snake family. Pit vipers are responsible for about 99% of the poisonous snakebites in the United States. Each year about 8,000 people in the United States fall victim to a venomous snakebite. However, only about 15 of those people die. Most deaths are due to rattlesnake bites. In comparison, coral snakes are responsible for about 25 bites a year in the United States.

Jellyfish, stingrays, sea urchins, sea anemones, barracudas, and coral pose a threat to those who live or vacation in coastal communities. The majority of stings received from marine animals happen in saltwater and are rarely life-threatening.

Causes & symptoms

The typical animal bite results in a laceration, tear, puncture, or crush injury. Cat bites are mostly found on the arms and hands, with deep puncture wounds that can reach to muscles, tendons, and bones. Human bites result from fights, sexual activity, and seizures. They may also be due to spousal or child abuse. Children often bite other children, but those bites are hardly ever severe. Human bites are capable of transmitting a wide range of dangerous diseases, including hepatitis B, syphilis , and tuberculosis .

People do not always feel a spider bite. In most cases, spider bites produce only minor symptoms. The first, and possibly only, evidence of a bite may be a mild swelling of the injured area and puncture marks or blisters . The affected area may be painful, itchy, or discolored. With more serious bites, there may be severe muscle cramps and rigidity of the abdominal muscles shortly after being bitten. Other possible symptoms include excessive sweating, nausea, vomiting , headaches, fever, chills, edema , and dizziness , as well as problems with breathing, vision, and speech. In addition, a brown spider's bite can lead to necrotic arachnidism, in which the tissue around the bite dies. This can produce an open sore that that can take years to heal completely. The symptoms of bee and wasp stings include pain , redness, swelling, and itchiness at the area of the sting. Multiple stings can have much more severe consequences. The danger signs of a severe allergic reaction, called anaphylactic shock, need immediate medical attention. They include nausea, chest pain, abdominal cramps, diarrhea , and difficulty swallowing or breathing.

Venomous pit viper bites usually begin to swell within 10 minutes and sometimes are painful. Other symptoms include edema at the wound site, skin blisters and discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Severe poisoning can lead to tingling sensations, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure, vomiting of blood, and coma. Coral snake bites are painful, and the effects of the venom may include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Nerves can become paralyzed, causing double vision, difficulty swallowing and speaking, and respiratory problems. Poisonous snakes often introduce little or no venom into the victim's body when they bite. The symptoms of these bites are not so severe. However, there is still a danger that the wounds can become infected by harmful microorganisms from the snake's mouth.

Jellyfish venom is delivered by barbs located on their tentacles. These barbs can penetrate the skin of people who brush up against them, even if the jellyfish is dead or the tentacle is severed from the body. Painful and itchy red lesions arise instantly on contact. The pain can continue up to 48 hours. Severe cases may lead to skin necrosis, muscle spasms and cramps, vomiting, nausea, diarrhea, headaches, excessive sweating, and other symptoms. In rare cases, jellyfish venom may cause cardiorespiratory failure.

Tail spines are the delivery mechanism for stingray venom. Stingray venom produces immediate, excruciating pain that lasts several hours. They cause deep puncture wounds, which may become infected if pieces of the spines become embedded in them. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhaging, a drop in blood pressure, and cardiac arrhythmia.

Signs of infection in a bite or sting site include redness, pain, swelling, warmth, and a discharge filled with pus. An inflammation of the connective tissue, called cellulitis, may also result. Sometimes systemic, and possibly life-threatening, infections develop, especially among those who are immunosuppressed.

Diagnosis

Most bites and stings are minor and do not need to be formally diagnosed. When required, though, diagnosis relies on a physical examination of the victim, information about the circumstances of the injury, and a look at the animal that caused the injury, if possible. It is especially important to retrieve the live animal or carcass of dogs, wild animals, snakes, and spiders for assessment. Information about tetanus immunization history and possible allergies to venom is important. A physical exam may be required to assess damage caused by deep puncture wounds or severe crush injuries. Chest x rays and electrocardiography may be required to assess severe symptoms. Laboratory tests for identifying the microorganisms may be ordered if there is an infection. Blood and urine tests also may be taken. Testing the blood for hepatitis B and other diseases is always necessary after a human bite, for example. Medical professionals should also look for indications of spousal or child abuse in cases of human bites.

Treatment

Some bites and stings, such as those from venomous snakes, require immediate medical attention, as do a host of others. So often, it is best to check with a medical/emergency practitioner first. Also, once a patient begins treating a bite or sting with an alternative method, if signs of infection or severe allergic reaction appear, he or she should seek immediate medical help.

Homeopathic remedies can be useful for relieving the pain and swelling of bites and stings. If there is a possible allergic reaction, these remedies can be used while awaiting emergency care. Aconitum can be helpful, especially if the person feels fearful or panicked after being stung. Aconitum should be used while symptoms are intense, and then can be followed a by another remedy, as indicated. Apis mellifica is especially useful for bee stings, and it can help to reduce the allergic reaction. Carbolicum acidum can also be used to treat an allergic reaction, especially when the person feels sick and weak and has trouble breathing. Cantharis, Ledum palustre, Hypericum, and Urtica urens are other useful remedies that may be indicated. A 6c or 12c dose of the chosen remedy can be taken every 15 minutes for up to four doses.

Neem , an Ayurvedan remedy, can be used to soothe minor bites and stings as well as to keep insects away. A thick paste can be made from neem powder blended with warm water. It can then be applied to the affected area twice daily. To prevent insect bites altogether, neem oil can be rubbed on exposed skin as a repellant. Another Ayurvedic remedy for soothing insect bites uses the herb cilantro. One cup of the fresh leaves should be mixed with 1/3 cup of water in a blender and strained. The juice should be stored in the refrigerator, and 2 tbsp can be taken three times per day. The pulp should be saved and applied directly to affected areas once or twice daily.

A compress made from meat tenderizer that contains either papain or bromelain breaks down the venom of bites and stings. This is because most venom is protein-based. The meat tenderizer functions by breaking down such proteins, which neutralizes the venom. A thick paste can be made using warm water or rubbing alcohol and powdered meat tenderizer and then applied directly to the affected areas for relief. Powdered bromelain or papain can also be used. The typical home's kitchen or medicine cabinet holds quick soothers for bee and wasp stings. Bicarbonate of soda or ammonia can soothe a bee sting and vinegar or lemon juice have been shown to help soothe wasp stings.

Allopathic treatment

Minor animal bites can be treated at home. The wound should be washed with soap and water. Applying pressure to the injured area with a clean towel or sterile bandage can stop bleeding. Antibiotic ointment and a sterile dressing can be applied to the wound if necessary. Alternately, to minimize swelling and infection, ice can be applied to the wound. Bites that do not stop bleeding after 15 minutes with pressure should be seen by a medical professional. Medical attention may also be required if there are signs of infection. People who have been bitten by a cat or by a human should always see a doctor. The same is true for snake bites; bites that are deep or gaping; bites to the head, hands, or feet; and bites that may be in conjunction with broken bones, damaged nerves, or any other major injury. If an unfamiliar animal bites, especially for no apparent reason, rabies may be suspected. A physician should be consulted. Dogs, raccoons, skunks, bats, coyotes, foxes, and ground hogs often carry rabies. In cases of suspected rabies, the victim will be given several injections with rabies vaccine. Diabetics, AIDS patients, cancer patients, people who have not had a tetanus shot in five years, and anyone else who has increased susceptibility to infection should also seek medical treatment for all bites and serious sting wounds.

Medical treatment may require the removal of dead and damaged tissue. Any patient whose tetanus shots are not up-to-date should receive a booster shot. Some wounds are left open and allowed to heal on their own, while others may require stitches. Antibiotics are usually limited to patients whose injuries or other health problems make them likely candidates for infection. Cat bites and human bites, however, are usually treated with antibiotics. The patient may also require immunization against hepatitis B and other diseases. A follow-up visit could be required.

An ice pack should be applied to the area of a spider bite as soon as it is discovered. Treatment for a serious spider bite may involve the administering of muscle relaxants, antihistamines, antibiotics, pain medication, and possibly a tetanus shot. Areas of necrosis may need debridement and skin grafts. An antivenin is available, but it is not necessary in most cases, and could possibly cause unpleasant side effects.

Most stings can be treated at home. A stinger can be scraped off the skin with a blade, fingernail, credit card, or stiff piece of paper. Tweezers are not recommended, since they may actually push more venom into the wound. The area should then be cleaned and covered with ice. Aspirin and other painkillers, antihistamines, and calamine lotion are good for reducing symptoms. People who experience an allergic reaction, or who are at risk for one, should seek immediate medical attention. People who are allergic should carry emergency kits containing epinephrine to counter anaphylactic shock at all times. Ticks can be carefully removed at home using tweezers. It is important to be sure that the head of the tick is not left embedded in the skin. If symptoms such as fever, rash or pain develop after a tick bite, a physician should be consulted immediately.

Although most snakes are not poisonous, any snakebite should immediately be examined at a hospital. If there is time, the victim should wash the wound site with soap and water, and then keep the injured area still and at a level lower than the heart. The injured person should not have anything to eat or drink, especially alcohol, until an evaluation and treatment is obtained. There is controversy about the use of tourniquets as well as sucking out venom. These should only be done when help is far away and by someone familiar with first aid techniques. Minor rattlesnake bites can be successfully treated without antivenin, as can the bites of copperhead and water moccasins. However, coral snake and the more dangerous rattlesnake bites require antivenin. Other treatment measures include antibiotics to prevent infection and a tetanus booster shot.

When dealing with bites or stings of marine animals, the victim should be kept still. Gloves should be worn when removing stingers. The area should be washed with saltwater and then soaked in very hot water for 30-90 minutes to neutralize the venom. Vinegar and other substances are used to neutralize jellyfish barbs, which are then scraped off. A doctor will usually examine stingray wounds to ensure that no pieces of the spines remain. Anesthetic ointments, antihistamine creams, and steroid lotions are sometimes beneficial. If the bites or stings are severe, they may require emergency care.

Expected results

Most bites and stings require little intervention, and clear up in a few hours or days. Those most at risk of severe problems with bites and stings are very young children, the elderly, those who are immunosuppressed, and people who are allergic to venom. Serious bites and stings require prompt treatment to ensure a favorable outcome. Infected bites may require hospitalization and can be fatal if neglected. In some cases, medication and surgery may be necessary. Some snakebites may result in amputation, permanent deformity, or loss of function in the injured area. People who are allergic to stings may experience a severe, and occasionally fatal, reaction.

Prevention

Insect repellant can help prevent insect bites and stings. Those with concentrated amounts of DEET stay effective longer. Sweet-scented fragrances should be avoided. Wearing white or khaki-colored clothing, including socks and long pants, helps protects the skin from bites or stings. Care and attention should always be used when going into wilderness areas. Posted warnings in swimming areas should be heeded. Unfamiliar animals should not be touched. Dead or dying animals should be avoided, as they may still be able to cause injury. When threatened by a dog, a person should remain still. If an attack seems unavoidable, lying face down with the hands and forearms covering sensitive areas may be the best protection. A rabies vaccine may be taken preventively if there is a high risk of exposure due to work or travel.

Resources

BOOKS

The Burton Goldberg Group. Alternative Medicine: The Definitive Guide. Washington: Future Medicine Publishing, 1993.

Bennett, J. Claude and Fred Plum, eds. Cecil Textbook of Medicine. Philadelphia: W.B. Saunders, 1996.

PERIODICALS

Kuritzky, Louis. "Comparative Efficacy of Insect Repellents Against Mosquito Bites." Primary Care Reports (September 2, 2002):S20.

PERIODICALS

"Pain Relief for Stings can be Found in the Kitchen Cabinet." Contemporary Pediatrics (August 2002):129–131.

PERIODICALS

Peterson, Lyle, and Anthony A. Martin. "West Nile Virus: A Primer for the Clinician." Annals of Internal Medicine (August 6, 2002):173–177.

OTHER

"Common First Aid Procedures: Bites and Stings." Columbia University College of Physicians & Surgeons Complete Home Medical Guide. http://cpmcnet.columbia.edu/texts/guide/hmg14_0004.html#14.6 (January 17, 2001).

Patience Paradox

Teresa G. Odle