Scabies

Definition

Scabies, also known as sarcoptic acariasis, is a contagious, parasitic skin infection caused by a tiny mite (sarcoptes scabiei ).

Description

Scabies is caused by a tiny, 0.3 mm-long, parasitic insect called a mite. When a human comes into contact with the female mite, the mite burrows under the skin, laying eggs along the lines of its burrow. These eggs hatch, and the resulting offspring rise to the surface of the skin; mate; and repeat the cycle either within the skin of the original host; or within the skin of its next victim, causing red lesions.

The intense itching , or pruritus, that is almost always caused by scabies is due to a reaction within the skin to the feces of the mite. The first time someone is infected with scabies, he or she may not notice any itching for four to six weeks. With subsequent infections , the itchiness will begin within hours of picking up the first mite.

Causes & symptoms

Scabies is most common among people who live in overcrowded conditions, and whose ability to practice good hygiene is limited. Scabies can be passed between people by close skin contact. Although the mites can only live away from human skin for about three days, sharing clothing or bedclothes can pass scabies among family members or close contacts. In May 2002, the Centers for Disease Control (CDC) included scabies in its updated guidelines for the treatment of sexually transmitted diseases.

Mite burrows within the skin are seen as winding, slightly raised gray lines along a person's skin. The female mite may be found at one end of the burrow, as a tiny pearl-like bump underneath the skin. Because of the intense itching, burrows may be obscured by scratch marks left by the patient. The most common locations for burrows include the sides of the fingers, between the fingers, the top of the wrists, around the elbows and armpits, around the nipples of the breasts in women, in the genitalia of men, around the waist (beltline), and on the lower part of the buttocks. Babies may have burrows on the soles of their feet, palms of their hands, and faces. The itching from scabies becomes worse after a hot shower and at night. Scratching, however, seems to serve some purpose in scabies, as the mites are apparently often inadvertently removed. Most infestations with scabies are caused by no more than 15 mites altogether.

Infestation with huge numbers of mites (on the order of thousands to millions) occurs when an individual does not scratch, or when an individual has a weakened immune system. These patients include those who live in institutions; are mentally retarded, or physically infirm; have other diseases which affect the amount of sensation they have in their skin (leprosy or syringomyelia); have leukemia or diabetes; are taking medications that lower their immune response (cancer chemotherapy, drugs given after organ transplantation); or have other diseases which lower their immune response (such as acquired immunodeficiency syndrome or AIDS ). This form of scabies, with its major infestation, is referred to as crusted scabies or Norwegian scabies. Infected patients have thickened crusty areas all over their bodies, including over the scalp. Their skin appears scaly, and their fingernails may be thickened and horny.

Diagnosis

Diagnosis can be made simply by observing the characteristic burrows of the mites causing scabies. A sterilized needle can be used to explore the pearly bump at the end of a burrow, remove its contents, and place it on a slide to be examined. The mite itself may then be identified under a microscope.

Occasionally, a type of mite carried on dogs (Sarcoptes scabiei var. canis ) may infect humans. These mites cannot survive for very long on humans, however, so the infection is less severe.

Treatment

A paste made from two herbs, neem (Azadirachta indica ) and turmeric (Curcuma longa,) applied to the affected area daily for 15 days has been found to be effective in treating scabies.

Allopathic treatment

Several types of lotions (usually containing 5% permethrin) can be applied to the body and left on for 12–24 hours. One topical application is usually sufficient, although the scabicide may be reapplied after a week if mites remain. Preparations containing lindane are no longer recommended for treating scabies as of 2003 because of the potential for damage to the nervous system. Itching can be lessened by the use of calamine lotion or antihistamine medications.

In addition to topical medications, the doctor may prescribe oral ivermectin. Ivermectin is a drug that was originally developed for veterinary practice as a broad-spectrum antiparasite agent. Studies done in humans, however, have found that ivermectin is as safe and effective as topical medications for treating scabies. A study published in 2003 reported that ivermectin is safe for people in high-risk categories, including those with compromised immune systems.

Expected results

The prognosis for complete recovery from a scabies infestation is excellent. In patients with weak immune systems, the biggest danger is that the areas of skin involved with scabies will become secondarily infected with bacteria.

Prevention

Good hygiene is essential in the prevention of scabies. When a member of a household is diagnosed with scabies, all that person's recently worn clothing and bedding should be washed in very hot water. Extensive cleaning of the household, however, is not necessary because the mite does not live long away from the human body.

Resources

BOOKS

Darmstadt, Gary L., and Al Lane. "Arthropod Bites and Infestations." In Nelson Textbook of Pediatrics, edited by Richard Behrman. Philadelphia: W.B. Saunders Co., 1996.

Maguire, James H. "Ectoparasite Infestations and Arthropod Bites and Stings." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw–Hill, 1998.

"Scabies (The Itch)." Section 10, Chapter 114 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.

Stoffman, Phyllis. The Family Guide to Preventing and Treating 100 Infectious Diseases. New York: John Wiley and Sons, Inc., 1995.

PERIODICALS

Burroughs, R. F., and D. M. Elston. "What's Eating You? Canine Scabies." Cutis 72 (August 2003): 107–109.

Burstein, G. R., and K. A. Workowski. "Sexually Transmitted Diseases Treatment Guidelines." Current Opinion in Pediatrics 15 (August 2003): 391–397.

Fawcett, R. S. "Ivermectin Use in Scabies." American Family Physician 68 (September 15, 2003): 1089–1092.

Santoro, A. F., M. A. Rezac, and J. B. Lee. "Current Trend in Ivermectin Usage for Scabies." Journal of Drugs in Dermatology 2 (August 2003): 397–401.

ORGANIZATIONS

American Academy of Dermatology (AAD). 930 East Woodfield Road, Schaumburg, IL 60173. (847) 330-0230. <http://www.aad.org>.

Kathleen D. Wright

Rebecca J. Frey, PhD

Scabies

Definition

Scabies is a relatively contagious infection caused by a tiny mite(Sarcoptes scabiei ).

Description

Scabies is caused by a tiny insect about 0.3 mm long called a mite. When a human comes in contact with the female mite, the mite burrows under the skin, laying eggs along the line of its burrow. These eggs hatch, and the resulting offspring rise to the surface of the skin, mate, and repeat the cycle either within the skin of the original host, or within the skin of its next victim.

The intense itching almost always caused by scabies is due to a reaction within the skin to the feces of the mite. The first time someone is infected with scabies, he or she may not notice any itching for a number of weeks (four to six weeks). With subsequent infections, the itchiness will begin within hours of picking up the first mite.

Causes and symptoms

Scabies is most common among people who live in overcrowded conditions, and whose ability to practice good hygiene is limited. Scabies can be passed between people by close skin contact. Although the mites can only live away from human skin for about three days, sharing clothing or bedclothes can pass scabies among family members or close contacts. In May 2002, the Centers for Disease Control (CDC) included scabies in its updated guidelines for the treatment of sexually transmitted diseases.

The itching, or pruritus, from scabies is worse after a hot shower and at night. Burrows are seen as winding, slightly raised gray lines along the skin. The female mite may be seen at one end of the burrow, as a tiny pearl-like bump underneath the skin. Because of the intense itching, burrows may be obscured by scratch marks left by the patient. The most common locations for burrows include the sides of the fingers, between the fingers, the top of the wrists, around the elbows and armpits, around the nipples of the breasts in women, in the genitalia of men, around the waist (beltline), and on the lower part of the buttocks. Babies may have burrows on the soles of their feet, palms of their hands, and faces.

Scratching seems to serve some purpose in scabies, as the mites are apparently often inadvertently removed. Most infestations with scabies are caused by no more than 15 mites altogether.

Infestation with huge numbers of mites (on the order of thousands to millions) occurs when an individual does not scratch, or when an individual has a weakened immune system. These patients include those who live in institutions; are mentally retarded, or physically infirm; have other diseases which affect the amount of sensation they have in their skin (leprosy or syringomyelia); have leukemia or diabetes; are taking medications which lower their immune response (cancerchemotherapy, drugs given after organ transplantation); or have other diseases which lower their immune response (such as acquired immunodeficiency syndrome or AIDS ). This form of scabies, with its major infestation, is referred to as crusted scabies or Norwegian scabies. Infected patients have thickened, crusty areas all over their bodies, including over the scalp. Their skin is scaly. Their fingernails may be thickened and horny.

Diagnosis

Diagnosis can be made simply by observing the characteristic burrows of the mites causing scabies. A sterilized needle can be used to explore the pearly bump at the end of a burrow, remove its contents, and place it on a slide to be examined. The mite itself may then be identified under a microscope.

Occasionally, a type of mite carried on dogs (Sarcoptes scabiei var. canis ) may infect humans. These mites cannot survive for very long on humans, and so the infection is very light.

Treatment

Several types of lotions (usually containing 5% permethrin) can be applied to the body, and left on for 12-24 hours. One topical application is usually sufficient, although the scabicide may be reapplied after a week if mites remain. Preparations containing lindane are no longer recommended for treating scabies as of 2003 because of the potential for damage to the nervous system. Itching can be lessened by the use of calamine lotion or antihistamine medications.

In addition to topical medications, the doctor may prescribe oral ivermectin. Ivermectin is a drug that was originally developed for veterinary practice as a broad-spectrum antiparasite agent. Studies done in humans, however, have found that ivermectin is as safe and effective as topical medications for treating scabies. A study published in 2003 reported that ivermectin is safe for people in high-risk categories, including those with compromised immune systems.

Prognosis

The prognosis for complete recovery from scabies infestation is excellent. In patients with weak immune systems, the biggest danger is that the areas of skin involved with scabies will become secondarily infected with bacteria.

Prevention

Good hygiene is essential in the prevention of scabies. When a member of a household is diagnosed with scabies, all that person's recently-worn clothing and bedding should be washed in very hot water.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Scabies (The Itch)." Section 10, Chapter 114 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Burroughs, R. F., and D. M. Elston. "What's Eating You? Canine Scabies." Cutis 72 (August 2003): 107-109.

Burstein, G. R., and K. A. Workowski. "Sexually Transmitted Diseases Treatment Guidelines." Current Opinion in Pediatrics 15 (August 2003): 391-397.

Fawcett, R. S. "Ivermectin Use in Scabies." American Family Physician 68 (September 15, 2003): 1089-1092.

Santoro, A. F., M. A. Rezac, and J. B. Lee. "Current Trend in Ivermectin Usage for Scabies." Journal of Drugs in Dermatology 2 (August 2003): 397-401.

ORGANIZATIONS

American Academy of Dermatology (AAD). 930 East Woodfield Road, Schaumburg, IL 60173. (847) 330-0230. 〈http://www.aad.org〉.

KEY TERMS

Mite— An insect parasite belonging to the order Acarina. The organism that causes scabies is a mite.

Pruritus— An unpleasant itching sensation. Scabies is characterized by intense pruritus.

Topical— A type of medication applied to the skin or body surface.

Scabies

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

BIBLIOGRAPHY

Introduction

Scabies is an infestation of the skin by the human itch mite, which is known as Sarcoptes scabiei. It occurs all around the world and is one of the most common skin problems reported to dermatologists. The word scabies comes from the Latin scabere, which means to scratch. There is a variant known as Norwegian scabies, which is very infectious and can lead to epidemics in places such as nursing homes, homeless shelters, and prisons. Scabies is caused by close human contact, including sexual contact, and leads to intense itching because of an immune response to the infestation.

Most healthy people can ward off an attack of scabies. But in those whose immunity is compromised because of HIV/AIDS or other factors, such as old age, the mites can take hold. Poor hygiene, malnutrition, and overcrowding are strong risk factors for an outbreak of scabies. Treatment is usually by a skin cream or tablets containing a drug that kills the mites.

Disease History, Characteristics, and Transmission

Mites are tiny organisms, barely visible to the human eye at around 0.4 millimeters in length. S. scabiei mate on human skin, after which the male dies. The fertilized female burrows through the epidermis—the outer layer of skin—and lays eggs in her “burrow.” Typically, around 10–15 organisms are found in an infestation giving rise to symptoms, although there can be many more in immunocompromised hosts, such as people with HIV/AIDS. Scabies arises from human contact, including sexual intercourse.

The symptoms of scabies come from the human immune response to the feces of the female mite in her burrow. There is severe itching—known clinically as pruritis—which is especially intense at night or after a hot shower or bath. This can occur in any part of the body, but is most common between the fingers, in the genitalia, and around the waist or other areas constricted by clothing. Among adults, scabies tends not to cause symptoms on the face, arm, neck, or soles of the feet, but these areas may be affected in children. Pustules— pimples filled with pus, a yellow fluid made up of dead white blood cells, bacteria, and bits of dead tissue—and blisters might occur in areas affected by scabies.

The so-called Norwegian variant of scabies, some times also called crusted scabies, of ten affects the face, scalp, palms of the hands, and soles of the feet. It may be mistaken for eczema or psoriasis, two other inflammatory skin conditions. Norwegian scabies is very contagious.

WORDS TO KNOW

ATOPY: Atopy is an inherited tendency towards hypersensitivity towards immunoglobulin E, a key component of the immune system, which plays an important role in asthma, eczema and hay fever.

MITE: A mite is a tiny arthropod (insect-like creature) of the order Acarina. Mites may inhabit the surface of the body without causing harm, or may cause various skin ailments by burrowing under the skin. The droppings of mites living in house-dust are a common source of allergic reactions.

PRURITIS: Pruritis is the medical term for itchiness.

PUSTULES: A pustule is a reservoir of pus visible just beneath the skin. It is usually sore to the touch and surrounded by inflamed tissue.

Scope and Distribution

Scabies is a worldwide problem, affecting 300–500 million people each year. It is more likely to occur where conditions of crowding, poor hygiene, and malnutrition are found. Accordingly, scabies is often seen in hospitals, nursing homes, prisons, and mental institutions.

Those with reduced immunity, such as patients with HIV/AIDS, are more prone to scabies and thousands to millions of S. scabiei eggs may be found under the skin of these individuals. Those with known atopy—that is, with hereditary, allergy-related symptoms such as asthma or eczema—may be more vulnerable to scabies, because of their sensitivity to the house dust mite, which is related to S. sabiei.

Treatment and Prevention

Scabies is treated by a 5% cream of permethrin, which is applied from the neck down to cover the whole body. Among young children, treatment of the face might also be needed. The treatment is left for several hours to kill the mites and is then washed away. This cures 90% of those infested. Oral ivermectin may also be useful, especially if the all-body topical treatment is hard to administer, as in nursing home residents. Meanwhile, clothing, bedding, and other items that might have been in touch with the mites should be washed.

Treatment of close contacts is also a good idea, to prevent reinfestation. Those treated may find their symptoms persist afterwards for four weeks or so because of the time needed to clear the body of the mite feces that cause the inflammatory response. The itching can be treated in all those affected by an antihistamine drug.

Impacts and Issues

Scabies is an uncomfortable disease that is largely a product of poor hygiene or crowded living conditions. It also targets those with compromised immunity, such as people with AIDS or the elderly. Therefore, those at risk need to be aware of the problem of scabies and take action to avoid close and prolonged contact with those who could already be infested.

IN CONTEXT: SOCIAL AND PERSONAL RESPONSIBILITY

The Division of Parasitic Diseases at Centers for Disease Control and Prevention (CDC) states the scabies is contracted by “direct, prolonged, skin-to-skin contact with a person already infested with scabies. Contact must be prolonged (a quick handshake or hug will usually not spread infestation). Infestation is easily spread to sexual partners and household members. Infestation may also occur by sharing clothing, towels, and bedding.”

The CDC further states that “anyone who is diagnosed with scabies, as well as his or her sexual partners and persons who have close, prolonged contact to the infested person should also be treated. If your health care provider has instructed family members to be treated, everyone should receive treatment at the same time to prevent reinfestation.”

SOURCE: Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases

See AlsoLice Infestation (Pediculosis).

BIBLIOGRAPHY

Books

Gates, Robert H. Infectious Disease Secrets. 2nd ed. Philadelphia: Hanley and Beltus, 2003.

Wilson, Walter R., and Merle A. Sande. Current Diagnosis & Treatment in Infectious Diseases. New York: McGraw Hill, 2001.

Scabies

Definition

Scabies is a relatively contagious infection caused by a tiny mite called Sarcoptes scabiei.

Description

Scabies is caused by a tiny insect about 0.3 mm long called a mite. When a human comes in contact with the female mite, the mite burrows under the skin, laying eggs along the line of its burrow. These eggs hatch, and the resulting offspring rise to the surface of the skin, mate, and repeat the cycle either within the skin of the original host or within the skin of its next victim.

The intense itching almost always caused by scabies is due to a reaction within the skin to the feces of the mite. The first time someone is infected with scabies, he or she may not notice any itching for a number of weeks (four to six weeks). With subsequent infections, the itchiness begins within hours of picking up the first mite.

Demographics

Prevalence rates are not clear; some studies suggest that between 6 and 27 percent of the population have scabies at any one time. Scabies is more common among schoolchildren and individuals living in crowded conditions.

Causes and symptoms

Scabies is most common among people who live in overcrowded conditions and whose ability to practice good hygiene is limited. Scabies can be passed between people by close skin contact. Although the mites can only live away from human skin for about three days, sharing clothing or bedclothes can pass scabies among family members or close contacts. In May 2002, the Centers for Disease Control (CDC) included scabies in its updated guidelines for the treatment of sexually transmitted diseases .

The itching (pruritus) from scabies is worse after a hot shower and at night. Burrows are seen as winding, slightly raised gray lines along the skin. The female mite may be seen at one end of the burrow, as a tiny pearl-like bump underneath the skin. Because of the intense itching, burrows may be obscured by scratch marks left by the patient. The most common locations for burrows are the sides of the fingers, between the fingers, the top of the wrists, around the elbows and armpits, around the nipples of the breasts in women, in the genitalia of men, around the waist (beltline), and on the lower part of the buttocks. Babies may have burrows on the soles of their feet, palms of their hands, and faces.

Scratching seems to serve some purpose in scabies, as the mites are apparently often inadvertently removed. Most infestations with scabies are caused by no more than 15 mites altogether.

Infestation with huge numbers of mites (on the order of thousands to millions) occurs when an individual does not scratch or when an individual has a weakened immune system. These patients include the elderly; those who live in institutions; the mentally retarded or physically infirm; those who have other diseases which affect the amount of sensation they have in their skin (leprosy or syringomyelia); leukemia or diabetes sufferers; those taking medications which lower their immune response (cancer chemotherapy or immunosuppressant drugs given after organ transplantation); or people with other diseases which lower their immune response (such as acquired immunodeficiency syndrome or AIDS ). This form of scabies, with its major infestation, is referred to as crusted scabies or Norwegian scabies. Infected patients have thickened, crusty areas all over their bodies, including over the scalp. Their skin is scaly. Their fingernails may be thickened and horny.

Diagnosis

Diagnosis can be made simply by observing the characteristic burrows of the mites causing scabies. A sterilized needle can be used to explore the pearly bump at the end of a burrow, remove its contents, and place it on a slide to be examined. The mite itself may then be identified under a microscope.

Occasionally, a type of mite carried on dogs (Sarcoptes scabiei var. canis ) may infect humans. These mites cannot survive for very long on humans, and so the infection is very light.

Treatment

Several types of lotions (usually containing 5% permethrin) can be applied to the body and left on for 12 to 24 hours. One topical application is usually sufficient, although the scabicide may be reapplied after a week if mites remain. Preparations containing lindane are no longer recommended for treating scabies because of the potential for damage to the nervous system. Itching can be lessened by the use of calamine lotion or antihistamine medications.

In addition to topical medications, the doctor may prescribe oral ivermectin, a drug that was originally developed for veterinary practice as a broad-spectrum antiparasite agent. Studies done in humans, however, have found that ivermectin is as safe and effective as topical medications for treating scabies. A study published in 2003 reported that ivermectin is safe for people in high-risk categories, including those with compromised immune systems.

Prognosis

The prognosis for complete recovery from scabies infestation is excellent. In patients with weak immune systems, the biggest danger is that the areas of skin involved with scabies will become secondarily infected with bacteria.

Prevention

Good hygiene is essential in the prevention of scabies. When a member of a household is diagnosed with scabies, all that person's recently worn clothing and bedding should be washed in very hot water.

Parental concerns

One of the biggest concerns among family members of an individual with scabies is its ready transmissibility. Care should be taken to avoid sharing bedding, towels, and clothing with an infected family member. Some healthcare providers recommend that all family members be treated with a scabicide, whether or not scabies is evident. Linens of all family members should be washed in the hottest water possible to avoid cross-contamination.

KEY TERMS

Mite —An insect parasite belonging to the order Acarina. The organism that causes scabies is a mite.

Pruritus —The symptom of itching or an uncontrollable sensation leading to the urge to scratch.

Topical —Not ingested; applied to the outside of the body, for example to the skin, eye, or mouth.

Resources

BOOKS

"Arthropod Bites and Infestations." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.

"Infestations and Bites." In Clinical Dermatology, 4th ed. Edited by Thomas P. Habif et al. St. Louis, MO: Mosby, 2004.

"Scabies." In Ferri's Clinical Advisor: Instant Diagnosis and Treatment. Edited by Fred F. Ferri. St. Louis, MO: Mosby, 2004.

ORGANIZATIONS

American Academy of Dermatology (AAD). 930 East Woodfield Road, Schaumburg, IL 60173. Web site: <www.aad.org>.Web sites

"Facts about Scabies." Available online at <www.safe2use.com/pests/scabies/scabies.htm> (accessed December 30, 2004).

Rosalyn Carson-DeWitt, MD Rebecca J. Frey, PhD

Scabies

Definition

Scabies is a relatively contagious infection caused by a tiny mite (Sarcoptes scabiei).

Description

Scabies is caused by a tiny insect about 0.3mmlongcalled a mite. When a human comes in contact with the female mite, the mite burrows under the skin, laying eggs along the line of its burrow. These eggs hatch, and the resulting offspring rise to the surface of the skin, mate, and repeat the cycle either within the skin of the original host, or within the skin of its next victim.

The intense itching almost always caused by scabies is due to a reaction within the skin to the feces of the mite. The first time someone is infected with scabies, he or she may not notice any itching for a number of weeks (four to six weeks). With subsequent infections, the itchiness will begin within hours of picking up the first mite.

Causes and symptoms

Scabies is most common among people who live in overcrowded conditions, and whose ability to practice good hygiene is limited. Scabies can be passed between people by close skin contact. Although the mites can only live away from human skin for about three days, sharing clothing or bedclothes can pass scabies among family members or close contacts. In May 2002, the Centers for Disease Control (CDC) included scabies in its updated guidelines for the treatment of sexually transmitted diseases .

The itching, or pruritus, from scabies is worse after a hot shower and at night. Burrows are seen as winding, slightly raised gray lines along the skin. The female mite may be seen at one end of the burrow, as a tiny pearl-like bump underneath the skin. Because of the intense itching, burrows may be obscured by scratch marks left by the patient. The most common locations for burrows include the sides of the fingers, between the fingers, the top of the wrists, around the elbows and armpits, around the nipples of the breasts in women, in the genitalia of men, around the waist (beltline), and on the lower part of the buttocks. Babies may have burrows on the soles of their feet, palms of their hands, and faces.

Scratching seems to serve some purpose in scabies, as the mites are apparently often inadvertently removed. Most infestations with scabies are caused by no more than 15 mites altogether.

Infestation with huge numbers of mites (on the order of thousands to millions) occurs when an individual does not scratch, or when an individual has a weakened immune system . These patients include those who live in institutions; are mentally retarded, or physically infirm; have other diseases which affect the amount of sensation they have in their skin (leprosy or syringomyelia); have leukemia or diabetes; are taking medications which lower their immune response (cancerchemotherapy, drugs given after organ transplantation); or have other diseases which lower their immune response (such as acquired immunodeficiency syndrome or AIDS ). This form of scabies, with its major infestation, is referred to as crusted scabies or Norwegian scabies. Infected patients have thickened, crusty areas all over their bodies, including over the scalp. Their skin is scaly. Their fingernails may be thickened and horny.

Diagnosis

Diagnosis can be made simply by observing the characteristic burrows of the mites causing scabies. A sterilized needle can be used to explore the pearly bump at the end of a burrow, remove its contents, and place it on a slide to be examined. The mite itself may then be identified under a microscope.

Occasionally, a type of mite carried on dogs (Sarcoptes scabiei var. canis) may infect humans. These mites cannot survive for very long on humans, and so the infection is very light.

Treatment

Several types of lotions (usually containing 5% permethrin) can be applied to the body, and left on for 12–24 hours. One topical application is usually sufficient, although the scabicide may be reapplied after a week if mites remain. Preparations containing lindane are no longer recommended for treating scabies as of 2003 because of the potential for damage to the nervous system. Itching can be lessened by the use of calamine lotion or antihistamine medications.

In addition to topical medications, the doctor may prescribe oral ivermectin. Ivermectin is a drug that was originally developed for veterinary practice as a broad-spectrum antiparasite agent. Studies done in humans, however, have found that ivermectin is as safe and effective as topical medications for treating scabies. A study published in 2003 reported that ivermectin is safe for people in high-risk categories, including those with compromised immune systems.

KEY TERMS

Mite —An insect parasite belonging to the order Acarina. The organism that causes scabies is a mite.

Pruritus —An unpleasant itching sensation. Scabies is characterized by intense pruritus.

Topical —A type of medication applied to the skin or body surface.

Prognosis

The prognosis for complete recovery from scabies infestation is excellent. In patients with weak immune systems, the biggest danger is that the areas of skin involved with scabies will become secondarily infected with bacteria.

Prevention

Good hygiene is essential in the prevention of scabies. When a member of a household is diagnosed with scabies, all that person's recently-worn clothing and bedding should be washed in very hot water.

Resources

books

Beers, Mark H., MD, and Robert Berkow, MD., editors. “Scabies (The Itch).” Section 10, Chapter 114 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

periodicals

Burroughs, R. F., and D. M. Elston. “What's Eating You? Canine Scabies.” Cutis 72 (August 2003):107–109.

Burstein, G. R., and K. A. Workowski. “Sexually Transmitted Diseases Treatment Guidelines.” Current Opinion in Pediatrics 15 (August 2003): 391–397.

Fawcett, R. S. “Ivermectin Use in Scabies.” American Family Physician 68 (September 15, 2003):1089–1092.

Santoro, A. F., M. A. Rezac, and J. B. Lee. “Current Trend in Ivermectin Usage for Scabies.” Journal of Drugs in Dermatology 2 (August 2003): 397–401.

ORGANIZATIONS

American Academy of Dermatology (AAD). 930 East Woodfield Road, Schaumburg, IL 60173. (847) 330-0230. http://www.aad.org.

Rosalyn Carson-DeWitt MD

Rebecca J. Frey Ph.D.