Botulism

Definition

Botulism is caused by botulinum toxin, a natural poison produced by certain bacteria in the Clostridium genus. Exposure to the botulinum toxin occurs mostly from eating contaminated food, or in infants, from certain clostridia growing in the intestine. Botulinum toxin blocks motor nerves' ability to release acetylcho-line, the neurotransmitter that relays nerve signals to muscles, and flaccid paralysis occurs. As botulism progresses, the muscles that control the airway and breathing fail.

Description

Botulism occurs rarely, but it causes concern because of its high fatality rate. Clinical descriptions of botulism possibly reach as far back in history as ancient Rome and Greece. However, the relationship between contaminated food and botulism wasn't defined until the late 1700s. In 1793 the German physician, Justinius Kerner, deduced that a substance in spoiled sausages, which he called wurstgift (German for sausage poison), caused botulism. The toxin's origin and identity remained elusive until Emile von Ermengem, a Belgian professor, isolated Clostridium botulinum in 1895 and identified it as the poison source.

Three types of botulism have been identified: foodborne, wound, and infant botulism. The main difference between types hinges on the route of exposure to the toxin. In the United States, there are approximately 110 cases of botulism reported annually. Food-borne botulism accounts for 25% of all botulism cases and usually can be traced to eating contaminated home-preserved food. Infant botulism accounts for 72% of all cases, but the recovery rate is good (about 98%) with proper treatment. From 1990 to 2000, 263 cases of food-borne cases were reported in the United States, most of them in Alaska. Though most were related to home canning, two restaurant-associated outbreaks affected 25 people.

Though domestic food poisoning is a problem world-wide, there has been a growing concern regarding the use of botulism toxin in biological warfare and terrorist acts. The Iraqi government admitted in 1995 that it had loaded 11,200 liters of botulinum toxin into SCUD missiles during the Gulf War. Luckily, these special missiles were never used. As of 1999, there were 17 countries known to be developing biological weapons, including the culture of botulism toxins.

Causes and symptoms

Toxin produced by the bacterium Clostridium botulinum is the main culprit in botulism. Other members of the clostridium genus can produce botulinum toxin, namely C. argentinense, C. butyricum, and C. baratii, but they are minor sources. To grow, these bacteria require a low-acid, oxygen-free environment that is warm (40-120°F or 4.4-48.8°C) and moist. Lacking these conditions, the bacteria transform themselves into spores that, like plant seeds, can remain dormant for years. Clostridia and their spores exist all over the world, especially in soil and aquatic sediments. They do not threaten human or animal health until the spores encounter an environment that favors growth. The spores then germinate, and the growing bacteria produce the deadly botulism toxin.

Scientists have discovered that clostridia can produce at least seven types of botulism toxin, identified as A, B, C, D, E, F, and G. Humans are usually affected by A, B, E, and very rarely F. Domesticated animals such as dogs, cattle, and mink are affected by botulism C toxin, which also affects birds and has caused massive die-offs in domestic bird flocks and wild waterfowl. Botulism D toxin can cause illness in cattle, and horses succumb to botulism A, B, and C toxin. There have been no confirmed human or animal botulism cases linked to the G toxin.

In humans, botulinum toxin latches onto specific proteins in nerve endings and irreversibly destroys them. These proteins control the release of acetylcholine, a neurotransmitter that stimulates muscle cells. With acetylcholine release blocked, nerves are not able to stimulate muscles. Ironically, botulinum toxin has found a beneficial niche in the world of medicine due to this action. Certain medical disorders are characterized by involuntary and uncontrollable muscle contractions. Medical researchers have discovered that injecting a strictly controlled dose of botulinum toxin into affected muscles inhibits excessive muscle contractions. The muscle is partially paralyzed and normal movement is retained. This is commonly referred to as Botox injection.

The three types of human botulism include the following symptoms:

• Food-borne. Food that has been improperly preserved or stored can harbor botulinum toxin-producing clostridia. Botulism symptoms typically appear within 18-36 hours of eating contaminated food, with extremes of four hours to eight days. Initial symptoms include blurred or double vision and difficulty swallowing and speaking. Possible gastrointestinal problems include constipation, nausea, and vomiting. As botulism progresses, the victim experiences weakness or paralysis, starting with the head muscles and progressing down the body. Breathing becomes increasingly difficult. Without medical care, respiratory failure and death are very likely.
• Infant. Infant botulism was first described in 1976. Unlike adults, infants younger than 12 months are vulnerable to C. botulinum colonizing the intestine. Infants ingest spores in honey or simply by swallowing spore-containing dust. The spores germinate in the large intestine and, as the bacteria grow, they produce botulinum toxin that is absorbed into the infant's body. The first symptoms include constipation, lethargy, and poor feeding. As infant botulism progresses, sucking and swallowing (thus eating) become difficult. A nursing mother will often notice breast engorgement as the first sign of her infant's illness. The baby suffers overall weakness and cannot control head movements. Because of the flaccid paralysis of the muscles, the baby appears "floppy." Breathing is impaired, and death from respiratory failure is a very real danger.
• Wound. Confirmed cases of wound botulism have been linked to trauma such as severe crush injuries to the extremities, surgery, and illegal drug use. Wound botulism occurs when clostridia colonize an infected wound and produce botulinum toxin. The symptoms usually appear four to 18 days after an injury occurs and are similar to food-borne botulism, although gastrointestinal symptoms may be absent.

KEY TERMS

Acetylcholine— A chemical released by nerve cells to signal other cells.

Antitoxin— A substance that inactivates a poison (e.g., toxin) and protects the body from being injured by it.

CT scan— The abbreviated term for computed or computerized axial tomography. The test may involve injecting a radioactive contrast into the body. Computers are used to scan for radiation and create cross-sectional images of internal organs.

Electromyographic test— A medical test which determines if a muscle's response to electrical stimuli. The test results allow medical personnel to assess how nerves to the muscle are functioning.

Flaccid paralysis— Paralysis characterized by limp, unresponsive muscles.

Lumbar puncture— A procedure in which a small amount of cerebrospinal fluid is removed from the lower spine. Examination of this fluid helps diagnose certain illnesses.

MRI— The abbreviated term for magnetic resonance imaging. MRI uses a large circular magnet and radio waves to generate signals from atoms in the body. These signals are used to construct images of internal structures.

Neurotransmitter— A chemical found in nerves that relays nerve signals to other cells. Acetylcholine is a neurotransmitter.

Sepsis— The presence of infection-causing organisms or associated toxins in the blood or within body tissues.

Spores— A state of "suspended animation" that some bacteria can adopt when conditions are not ideal for growth. Spores are analogous to plant seeds and can germinate into growing bacteria when conditions are right.

Toxin— A poisonous substance produced by a microorganism, plant, or animal.

Tracheostomy— The procedure used to open a hole in the neck to the trachea, or windpipe. It is sometimes used in conjunction with a respirator.

Diagnosis

Diagnosis of botulism can be tricky because symptoms mimic those presented by other diseases. Botulism may be confused with Guillain-Barre syndrome, myasthenia gravis, drug reactions, stroke, or nervous system infection, intoxications (e.g. carbon monoxide or atropine), or shellfish poisoning. Sepsis is the most common initial diagnosis for infant botulism. Failure to thrive may also be suspected. Some reports have linked infant botulism to 5-15% of sudden infant death syndrome (SIDS, crib death) cases. Laboratory tests are used for definitive diagnosis, but if botulism seems likely, treatment starts immediately.

While waiting for laboratory results, doctors ask about recently consumed food and work to dismiss other disease possibilities. A physical examination is done with an emphasis on the nervous system. As part of this examination, CT scans, MRIs, electromyographic tests, or lumbar punctures may be ordered. Laboratory tests involve testing a suspected food and/ or the patient's serum, feces, or other specimens for traces of botulinum toxin or clostridia.

Treatment

Drugs

Adults with botulism are treated with an antitoxin derived from horse serum that is distributed by the Centers for Disease Control and Prevention. The antitoxin (effective against toxin types A, B, and E) inactivates only the botulinum toxin that is unattached to nerve endings. Early injection of antitoxin (usually within 24 hours of onset of symptoms) can preserve nerve endings, prevent progression of the disease, and reduce mortality.

Infants, however, cannot receive the antitoxin used for adults. For them, human botulism immune globulin (BIG) is available in the United States through the Infant Botulism Treatment and Prevention Program in Berkeley, California. BIG neutralizes toxin types A, B, C, D, and E before they can bind to nerves. This antitoxin can provide protection against A and B toxins for approximately four months. Though many infants recover with supportive care, BIG cuts hospital stay in half, and therefore reduces hospital costs by 50% as well.

Aside from antitoxin, no drugs are used to treat botulism. Antibiotics are not effective for preventing or treating botulism. In fact, antibiotic use is discouraged for infants because dying bacteria could potentially release more toxin into a baby's system. Antibiotics can be used, however, to treat secondary respiratory tract and other infections.

Respiratory support

Treatment for infants usually involves intensive respiratory support and tube feeding for weeks or even months. Once an infant can breathe unaided, physical therapy is initiated to help the child relearn how to suck and swallow. A respirator is often required to help adult patients breathe, and a tracheostomy may also be necessary.

Surgery

Surgery may be necessary to clean an infected wound and remove the source of the bacteria that is producing the toxin. Antimicrobial therapy may be necessary.

Gastric lavage

When botulism is caused by food, it often is necessary to flush the gastrointestinal tract (gastric lavage). Often cathartic agents or enemas are used. It is important to avoid products that contain magnesium, since magnesium enhances the effect of the toxin.

Prognosis

With medical intervention, botulism victims can recover completely, though slowly. It takes weeks to months to recover from botulism, and severe cases can take years before a total recovery is attained. Recovery depends on the nerve endings building new proteins to replace those destroyed by botulinum toxin.

Prevention

Vaccines against botulism do not exist to prevent infant botulism or other forms of the disease. However, scientists announced in 2004 that they had successfully vaccinated mice and ducks against type C and D, which may help lead to vaccines for humans. Food safety is the surest prevention for botulism. Botulinum toxin cannot be seen, smelled, or tasted, so the wisest course is to discard any food that seems spoiled without tasting it. Home canners must be diligent about using sterile equipment and following U.S. Department of Agriculture canning guidelines. If any part of a canned food container is rusty or bulging, the food should not be eaten. Infant botulism is difficult to prevent, because controlling what goes into an infant's mouth is often beyond control, especially in regard to spores in the air. One concrete preventive is to never feed honey to infants younger than 12 months since it is one known source of botulism spores. As infants begin eating solid foods, the same food precautions should be followed as for adults.

Resources

PERIODICALS

Cadou, Stephanie G. "Diagnosing Infant Botulism." The Nurse Practitioner 26, no.3 (March 2001): 76.

Shapiro, Roger L. and David L. Swerdlow. "Botulism: Keys to Prompt Recognition and Therapy." Consultant (April 1999): 1021-1024.

Sobel, Jeremy, et al. "Foodborne Botulism in the United States, 1990–2000." Emerging Infectious Diseases (September 2004): 1606-1612.

"Vaccination With Botulinum Neurotoxin Fragments Prevents Botuism." Obesity, Fitness & Wellness Week (August 7, 2004): 117.

Botulism

Definition

Botulism is an acute, progressive condition caused by botulinum toxin, a natural poison produced by the spore-forming bacteria Clostridium botulinum. Exposure to the botulinum toxin usually occurs from eating contaminated food although, in infants, it may be caused by specific types of clostridia obtained from soil or inhaled spores, causing growth of the bacteria in the infant's intestine. Botulinum toxin is a neurotoxin that blocks the ability of motor nerves to release acetylcholine, the neurotransmitter that relays nerve signals to muscles, a process that may result in unresponsive muscles, a condition known as flaccid paralysis. Breathing may be severely compromised in progressive botulism because of failure of the muscles that control the airway and breathing.

Description

Botulism occurs only rarely, but its high fatality rate makes it a great concern for those in the general public and in the medical community. Clinical descriptions of botulism reach as far back in history as ancient Rome and Greece. However, the relationship between contaminated food and botulism was not defined until the late 1700s. In 1793 the German physician, Justinius Kerner (1786–1862), deduced that a substance in spoiled sausages, which he called wurstgift (German for sausage poison), caused botulism. The toxin's origin and identity remained vague until Emile van Ermengem (1851–1932), a Belgian professor, isolated Clostridium botulinum in 1895 and identified it as the source of food poisoning .

Three types of botulism have been identified: food-borne, wound, and infant botulism. The main difference between types hinges on the route of exposure to the toxin. Food-borne botulism accounts for 25 percent of all botulism cases and can usually be traced to eating contaminated home-preserved food. Infant botulism accounts for 72 percent of all cases. About 98 percent of infants recover with proper treatment. Although domestic food poisoning is a problem worldwide, concern is growing regarding the use of botulism toxin in biological warfare. At the end of the twentieth century 17 countries were known to be developing biological weapons, including the culture of botulism toxins.

Transmission

Botulism is not spread from one individual to another, but through exposure to the deadly botulinum toxin, a natural poison produced by certain Clostridium bacteria that may be found in preserved, especially canned, foods and sometimes in the intestines of infants. Botulism spores can cause widespread illness if introduced into the environment.

Demographics

Botulism occurs worldwide, with 90 percent of the comparatively rare cases occurring in the United States. Approximately 110 cases of botulism are reported annually in the United States, with 50 percent of cases in California alone. Infant botulism accounts for 72 percent of all cases, far exceeding both food-borne and wound botulism. Food-borne botulism accounts for 25 percent of all cases, primarily due to eating contaminated home-preserved food.

Causes and symptoms

Toxins produced by the bacterium Clostridium botulinum are the main culprit in botulism. Other members of the Clostridium genus can produce botulinum toxin, namely C. argentinense, C. butyricum, and C. baratii, but these are minor sources. To grow, these bacteria require a low-acid, oxygen-free environment that is warm (40–120°F or 4.4–48.8°C) and moist. Lacking these conditions, the bacteria transform themselves into spores that, like plant seeds, can remain dormant for years. Clostridia and their spores exist all over the world, especially in soil and aquatic sediments. They do not threaten human or animal health until the spores encounter an environment that favors growth. The spores then germinate, and the growing bacteria produce the deadly botulism toxin.

Scientists have discovered that clostridia can produce at least seven types of botulism toxin, identified as A, B, C, D, E, F, and G. Humans are usually affected by A, B, E, and very rarely F; infants are affected by types A and B. Domesticated animals such as dogs, cattle, and mink are affected by botulism C toxin, which also affects birds and has caused massive die-offs in domestic bird flocks and wild waterfowl. Botulism D toxin can cause illness in cattle, and horses succumb to botulism A, B, and C toxin. There have been no confirmed cases of human or animal botulism linked to the G toxin.

In humans, botulinum toxin latches onto specific proteins in nerve endings and irreversibly destroys them. These proteins control the release of acetylcholine, a neurotransmitter that stimulates muscle cells. With acetylcholine release blocked, nerves are not able to stimulate muscles. Ironically, this action of the botulinum toxin has given it a beneficial niche in the world of medicine. Certain medical disorders are characterized by involuntary and uncontrollable muscle contractions. Medical researchers have discovered that injecting a strictly controlled dose of botulinum toxin into affected muscles inhibits excessive muscle contractions. The muscle is partially paralyzed and normal movement is retained.

Human botulism (caused by botulism toxins A, B, and E) may stem from contaminated food, wound contamination, or the intestinal botulism toxin found in infants. Each produces multiple symptoms as follows:

• Food-borne botulism. Food that has been improperly preserved or stored can harbor botulinum toxin-producing clostridia. Canned or jarred baby food has also been known to cause botulism. Symptoms of food-borne botulism typically appear within 18 to 36 hours of eating contaminated food, with extremes of four hours to eight days. Initial symptoms include blurred or double vision and difficulty swallowing and speaking. Possible gastrointestinal problems include constipation , nausea , and vomiting . As botulism progresses, the victim experiences weakness or paralysis, starting with the head muscles and progressing down the body. Breathing becomes increasingly difficult. Without medical care, respiratory failure and death are very likely.
• Infant botulism. Infant botulism was first described in 1976. Unlike adults, infants younger than 12 months are vulnerable to C. botulinum colonizing the intestine. Infants ingest spores in honey or simply by swallowing spore-containing dust or dirt. The spores germinate in the large intestine and, once colonized, toxin is produced and absorbed into the infant's body from the entire intestinal tract. The first symptoms include constipation, lethargy, and poor feeding. As infant botulism progresses, sucking and swallowing (thus eating) become difficult. A nursing mother will often notice her own breast engorgement as the first sign of her infant's illness. The baby suffers overall weakness and cannot control head movements. Because of the flaccid paralysis of the muscles, the baby appears floppy. Breathing is impaired, and death from respiratory failure is a very real danger.
• Wound botulism. Confirmed cases of wound botulism have been linked to trauma such as severe crush injuries to the extremities, surgery, and illegal drug use. Wound botulism occurs when Clostridia colonize an infected wound and produce botulinum toxin. The symptoms usually appear four to 18 days after an injury occurs and are similar to food-borne botulism, although gastrointestinal symptoms may be absent.

When to call the doctor

Infant botulism may be hard for parents to identify because the symptoms occur slowly. Parents should call the doctor or take the infant or child to emergency services as soon as the child shows symptoms such as weakness or listlessness, lethargy, irritability, and poor eating (or nursing) along with decreased bowel movements or constipation. An affected child may be so weak as to appear floppy and not in control of muscle movements, especially movement of the neck and head. Whether parents are aware of a possible source of the botulism toxin, the suggestive symptoms should not be ignored.

Diagnosis

Differential diagnosis of botulism can be complex because the symptoms mimic those of other diseases, especially diseases characterized by muscle weakness. Botulism must be differentiated from diseases such as the following:

• Guillain-Barré syndrome
• meningoencephalitis
• myasthenia gravis
• systemic poisoning or sepsis
• reactions to therapeutic drugs
• nervous system infection
• carbon monoxide or atropine intoxication
• severe allergic reactions to bee sting, shell fish, and other allergens
• failure to thrive

Sepsis is the most common initial diagnosis for actual infant botulism, and meningoencephalitis may also be the diagnosis if irritability and lethargy are present. Infant botulism was at one time linked to 5 to 15 percent of cases of sudden infant death syndrome (SIDS, crib death) because of spores found in 4 to 15 percent of cases; however, a subsequent 10-year study did not find a significant influence of botulism on SIDS.

Laboratory tests are used to make a definitive diagnosis, but if botulism seems likely, treatment starts immediately without waiting for test results, which may take up to two days. Diagnostic tests focus on identifying the organism causing the illness. This may involve performing a culture on contaminated material from the suspect food or the nose or throat of the affected individual. In infant botulism, the infant's stool may be cultured to isolate the organism; this test may be performed by the state health department or the Centers for Disease Control (CDC). Culture results are available from the microbiology laboratory as soon as bacteria grow in a special plate incubated at temperatures at or above body temperature. The growth of Clostridium confirms the diagnosis. Sometimes the organism cultured is not Clostridium as suspected. The microbiology laboratory may use samples of the bacteria grown to perform other special techniques in order to help identify the causative organism.

While waiting for diagnostic test results, doctors ask about recently consumed food, possible open sores, recent activities and behavior, and other factors that may help to rule out other disease possibilities. A physical examination is done with an emphasis on the nervous system and muscle function. As part of this examination, imaging studies such as CT and MRI may be done and electrodiagnostic muscle function tests (electromyogram) or lumbar punctures may be ordered. Laboratory tests look for the presence of botulinum toxin or Clostridia in suspected foods and/or the child's blood serum, feces, or other specimens for traces of botulinum toxin or Clostridia. Magnesium levels may be measured, since magnesium increases the activity of Clostridium. Additional diagnostic tests may be done to rule out other diseases or conditions with similar symptoms.

Treatment

Drugs

Older children and adults with botulism are sometimes treated with an antitoxin derived from horse serum that is distributed by the Centers for Disease Control and Prevention. The antitoxin (effective against toxin types A, B, and E) inactivates only the botulinum toxin that is unattached to nerve endings. Early injection of the antitoxin, ideally within 24 hours of onset of symptoms, can preserve nerve endings, prevent progression of the disease, and reduce mortality.

Unfortunately, infants cannot receive the antitoxin used for adults. For them, human botulism immune globulin (BIG) is the preferred treatment. It is available in the United States through the Infant Botulism Treatment and Prevention Program in Berkeley, California. BIG neutralizes toxin types A, B, C, D, and E before they can bind to nerves. This antitoxin can provide protection against A and B toxins for approximately four months. Though many infants recover with supportive care, BIG cuts hospital stay in half and, therefore, reduces hospital costs by 50 percent as well.

Aside from the specific antitoxin, no therapeutic drugs are used to treat botulism. Antibiotics are not effective for preventing or treating botulism because the Clostridium group of toxins are not sensitive to them. In fact, antibiotic use is discouraged for infants because bacteria could potentially release more toxin into a baby's system as they are killed. Antibiotics can be used, however, to treat secondary respiratory tract and other infections.

Respiratory support

Treatment for infants usually requires them to be in an intensive care unit, involving intensive respiratory support and nasogastric tube feeding for weeks or even months. Once an infant can breathe unaided, physical therapy is initiated to help the child relearn how to suck and swallow. In older children and adults, a respirator is often required to assist breathing; a tracheostomy may be necessary in some cases.

Surgery

Surgery may be necessary to clean an infected wound (debridement) and remove the source of the bacteria producing the toxin. Antimicrobial therapy may be necessary.

Gastric lavage

When botulism in older children or adults is caused by food, it often is necessary to flush the gastrointestinal tract (gastric lavage). Often cathartic agents or enemas are used. It is important to avoid products that contain magnesium, since magnesium enhances the effect of the toxin.

Nutritional concerns

Parents should avoid feeding honey to infants younger than 12 months because it is one known source of botulism spores.

Prognosis

With medical intervention, botulism victims can recover completely, though it may be a very slow recovery. It takes weeks to months to recover from botulism, and severe cases can take years before a total recovery is attained. Recovery depends on the nerve endings building new proteins to replace those destroyed by botulinum toxin.

Prevention

Vaccines have not been developed directed against botulism, which makes prevention of infant botulism or other forms of the disease difficult, since exposure to the botulinum toxic is typically unrecognized. Food safety is the surest prevention for botulism. Botulinum toxin cannot be seen, smelled, or tasted, so the wisest course is to discard any food that seems spoiled; avoid eating food from dented, rusty, or bulging cans; avoid refreezing meats once they have been thawed; and avoid buying broken containers of food or eating food that has been stored at room temperature or above for more than a few hours. People who like to can food at home must be diligent about using sterile equipment and following U.S. Department of Agriculture canning guidelines.

Infant botulism is difficult to prevent, because controlling what goes into an infant's mouth is often beyond control, especially in regard to airborne spores. One concrete preventative is to never feed honey to infants younger than 12 months as it is one known source of botulism spores. As infants begin eating solid foods, the same food precautions should be followed as for older children and adults.

Parental concerns

Because symptoms of infant botulism appear slowly, parents may be concerned that they will be missed or not found early. Normal watchfulness of the parents is sufficient, paying attention to any change in feeding, a decrease in bowel movements, or a lack of normal responses such as turning of the head and body movements. It may be helpful to remember how rare botulism is, how easy it is to assure food safety, and also that morbidity and mortality can be avoided with early recognition of the symptoms.

KEY TERMS

Acetylcholine —A chemical called a neurotransmitter that functions primarily to mediate activity of the nervous system and skeletal muscles.

Antitoxin —An antibody against an exotoxin, usually derived from horse serum.

Computed tomography (CT) —An imaging technique in which cross-sectional x rays of the body are compiled to create a three-dimensional image of the body's internal structures; also called computed axial tomography.

Culture —A test in which a sample of body fluid is placed on materials specially formulated to grow microorganisms. A culture is used to learn what type of bacterium is causing infection.

Electrooculography (EOG) —A diagnostic test that records the electrical activity of the muscles that control eye movement.

Flaccid paralysis —Paralysis characterized by limp, unresponsive muscles.

Lumbar puncture —A procedure in which the doctor inserts a small needle into the spinal cavity in the lower back to withdraw spinal fluid for testing. Also known as a spinal tap.

Magnetic resonance imaging (MRI) —An imaging technique that uses a large circular magnet and radio waves to generate signals from atoms in the body. These signals are used to construct detailed images of internal body structures and organs, including the brain.

Neurotoxin —A poison that acts directly on the central nervous system.

Neurotransmitter —A chemical messenger that transmits an impulse from one nerve cell to the next.

Sepsis —A severe systemic infection in which bacteria have entered the bloodstream or body tissues.

Spore —A dormant form assumed by some bacteria, such as anthrax, that enable the bacterium to survive high temperatures, dryness, and lack of nourishment for long periods of time. Under proper conditions, the spore may revert to the actively multiplying form of the bacteria. Also refers to the small, thick-walled reproductive structure of a fungus.

Toxin —A poisonous substance usually produced by a microorganism or plant.

Tracheostomy —A procedure in which a small opening is made in the neck and into the trachea or windpipe. A breathing tube is then placed through this opening.

Resources

BOOKS

Rosaler, Maxine. Botulism. New York: Rosen Publishing Group, 2004.

PERIODICALS

Cadou, Stephanie G. "Diagnosing Infant Botulism." The Nurse Practitioner 26, no. 3 (March 2001): 76.

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: <www.cdc.gov>.

L. Lee Culvert Janie F. Franz

Botulism

What Is Botulism?

How Common Is Botulism?

How Can a Person Contract Botulism?

What Are the Signs and Symptoms of Botulism?

How Do Doctors Make the Diagnosis?

How Is Botulism Treated?

What Are the Complications and Duration of the Disease?

How Can Botulism Be Prevented?

Resource

Botulism (BOH-chu-lih-zum) is an uncommon, nerve-paralyzing illness caused by toxins* produced by Clostridium botulinum (klos-TRIH-deum boh-chu-LIE-num) bacteria.

KEYWORDS

for searching the Internet and other reference sources

Botulinum toxin

Clostridium botulinum

Food poisoning

Home-canned foods

Neurotoxin

Paralytic illness

What Is Botulism?

There are seven types of botulinum toxin, each designated by a letter from A through G. Only four types (A, B, E, and F) make people sick. There are three forms of naturally occurring human botulism: infant botulism, food-borne botulism, and wound botulism. Inhalation (in-huh-LAY-shun) botulism is an additional form of the illness that could possibly be spread through the air intentionally by man. Clostridium botulinum is commonly found in soil and grows best in low-oxygen environments. The bacteria form spores* that remain dormant, or inactive, waiting for conditions that allow them to grow. The spores can exist everywhere, and people might eat food containing these spores without becoming sick. When conditions are right, however, the spores can activate and produce toxin.

*toxins

are poisons that harm the body.

*spores

are a temporarily inactive form of a germ enclosed in a protective shell.

Food contaminated with the toxin is the culprit in cases of food-borne botulism; most outbreaks stem from food that is improperly cooked or incorrectly canned or preserved. In food-borne botulism the toxin itself is swallowed, but in cases of infant botulism an infant swallows the spores and they then activate in the intestine and produce toxin. It is believed that the infant intestine lacks enough protective intestinal bacteria, stomach acid, and immune globulins* to prevent the spores from activating. Wound botulism is rare and develops when bacteria infect a wound and grow, producing the toxin. Bioterrorists have attempted to aerosolize* botulinum toxin without success, but the threat of inhalation botulism as a biological weapon has raised concerns.

*immune globulins

(ih-MYOON GLAH-byoo-linz), also called gamma globulins, are the proteins of which antibodies are composed.

*aerosolize

(AIR-o-suh-lize) is to put something, such as a medication, in the form of small particles or droplets that can be sprayed or released into the air.

How Common Is Botulism?

More than 100 cases of botulism are reported in the United States each year. Infant botulism accounts for about 72 percent of reported cases and food-borne botulism for about 25 percent. Wound botulism is the rarest form, but health officials have noted an increase in this type in California, a rise they attribute to the intravenous* use of illegal drugs from Mexico.

*intravenous

(in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin’s surface directly into a vein.

How Can a Person Contract Botulism?

Botulism is not contagious. Outbreaks of food-borne botulism usually can be traced to improperly home-canned foods, especially those with low amounts of acid, such as asparagus, green beans, beets, and corn, which allow the Clostridium botulinum bacteria to grow. Various frozen foods also have been implicated in outbreaks of the disease. Most infants contract botulism by inhaling or swallowing spores; honey is one source of these spores. Wound botulism sometimes is linked to crush injuries.

What Are the Signs and Symptoms of Botulism?

The classic symptoms of botulism include blurred or double vision*, droopy eyelids, slurred speech, difficulty in swallowing, dry mouth, and muscle weakness. These symptoms appear when the toxin interrupts nerve impulses to the muscles, which paralyzes the muscles. If untreated, paralysis may progress to involve the arms, legs, trunk, and muscles of the respiratory tract*. In food-borne botulism, symptoms generally begin 18 to 36 hours after eating the contaminated food, but they can occur after as little as 6 hours or as much as 10 days. Infants with botulism may appear drowsy or sluggish, not eat well, be constipated, and have a weak cry and muscle weakness. In infants, it can take 3 to 30 days for the symptoms to appear and progress.

*double vision

is a vision problem in which a person sees two images of a single object.

*respiratory tract

includes the nose, mouth, throat, and lungs. It is the pathway through which air and gases are transported down into the lungs and back out of the body.

How Do Doctors Make the Diagnosis?

Laboratory tests can detect the toxin in blood, stool (bowel movements), or wound samples. Because the symptoms of botulism are similar to those of stroke* and several other nerve diseases, doctors also may order a brain scan, spinal tap*, or other nerve- and muscle-function tests to check for other possible causes. The doctor may ask whether the patient has eaten any home-canned foods and, if so, order tests on the suspect food.

*stroke

is a brain-damaging event usually caused by interference with blood flow to the brain. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, do not properly function.

*spinal tap,

also called a lumbar puncture, is a medical procedure in which a needle is used to withdraw a sample of the fluid surrounding the spinal cord and brain. The fluid is then tested, usually to detect signs of infection, such as meningitis, or other diseases.

How Is Botulism Treated?

The U.S. Centers for Disease Control and Prevention (CDC) has a supply of antitoxin* against botulism. The antitoxin can slow or halt the damage caused by botulinum toxin. The sooner it is given, the more effective it is in easing the symptoms. To help rid the body of the toxin, doctors sometimes cause vomiting or use enemas*. In severe cases, patients who are unable to breathe well enough on their own might need a ventilator (VEN-tuh-lay-ter), a machine that can help a person breathe for several weeks. Wound botulism might require surgery to remove the source of the toxin-producing bacteria.

*antitoxin

(an-tih-TOK-sin) counteracts the effects of toxins, or poisons, on the body. It is produced to act against specific toxins, like those made by the bacteria that cause botulism or diphtheria.

*enemas

(EH-nuh-muhz) are procedures in which liquid is injected through the anus into the intestine, usually to flush out the intestines.

What Are the Complications and Duration of the Disease?

Most people with botulism require hospitalization, but they typically recover after weeks or perhaps months of care. Paralysis of the respiratory muscles can lead to pneumonia*. Even after recovery, some patients may be tired and feel short of breath.

*pneumonia

(nu-MO-nyah) is inflammation of the lung, usually caused by infection.

How Can Botulism Be Prevented?

Although botulinum toxin is extremely potent, it can be destroyed easily. Heating food and drinks to an internal temperature of 185 degrees Fahrenheit for at least 5 minutes will detoxify them. Boiling home-canned foods before eating them also lessens risk. Health officials advise using a pressure cooker and high temperatures—about 250 degrees Fahrenheit—to kill the spores when canning or preserving foods at home. It also is best to avoid eating commercially prepared foods from cans that are swollen, punctured, or leaking. Because honey can contain spores of Clostridium botulinum, doctors advise that infants younger than 1 year not be given this sweetener. Breast-feeding can help protect against infant botulism. Receiving prompt medical care for infected wounds and not injecting street drugs can help prevent wound botulism.

Clostridium botulinum bacteria as seen with an electron microscope. Visuals Unlimited

See also

Resource

Website

KidsHealth.org. KidsHealth is a website created by the medical experts of the Nemours Foundation and is devoted to issues of children’s health. It contains articles on a variety of health topics, including botulism. http://www.KidsHealth.org

For Good and Evil

Botulinum toxin is the first biological toxin licensed for treatment of human diseases. The U.S. government approves its use to relax painfully cramped or tight muscles and as an ingredient in medications for the treatment of migraine headache, chronic lower back pain, stroke, brain injury, and cerebral palsy. Botulinum toxin injections (called Botox) can paralyze muscles that cause the skin to wrinkle. Their use is popular among people looking to maintain a youthful appearance.

Ironically, the same substance has the potential to cause mass destruction if it is dispersed into the air or introduced into the food supply. The U.S. government developed botulinum toxin for potential use as a weapon during World War II. Japan, Iraq, and the Soviet Union have also experimented with botulinum toxin as a biological weapon, and Iran, North Korea, and Syria may have done so as well.

However, scientists have been perplexed and terrorists thwarted by how difficult it is to prepare botulism toxin for use as a weapon. Terrorists in Japan attempted to unleash it on at least three occasions between 1990 and 1995, but their plan for widespread destruction failed each time. In addition to tracking the efforts of bioterrorists, the U.S. government has developed elaborate methods to detect and respond to an attack with botulinum toxin. A national surveillance system involving doctors and hospitals has been designed to alert the U.S. Centers for Disease Control and Prevention to botulism outbreaks, and stores of antitoxin are on hand to treat victims.

Botulism

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

BIBLIOGRAPHY

Introduction

Botulism is a disease that is caused by a bacterial toxin. The toxin is one of seven (A-G) made and released by the bacterium Clostridium botulinum. Botulism toxin types A, B, E, and F cause botulism in humans. Another bacterium called Clostridium baratii can also produce a disease-causing toxin, but this bacterium is rarely encountered, and is responsible for far fewer cases of botulism than is C. botulinum.

Botulism toxins are powerful neurotoxins; they affect nerves and can produce paralysis. One microgram of toxin—a millionth of a gram—can kill a person. Paralysis from botulism affects the functioning of organs and tissues, and when botulism is fatal, it is usually due to failure of the respiratory muscles.

Disease History, Characteristics, and Transmission

Botulism was first described in 1735 in an illness outbreak that was traced to the consumption of contaminated German sausage. Indeed, the word botulism was derived from the Latin word botulus, meaning sausage.

C. botulinum are commonly found in soil. They can be present on vegetables and other food grown in soil, and can be eaten if the food is not completely washed free of bacteria. Fortunately, under these conditions where oxygen is present, the bacteria do not produce the toxin and so are harmless when eaten. Botulism is not a contagious disease—it cannot be spread from person to person. Rarely, botulism occurs as the result of a wound infected with C. botulinum.

The toxin is produced when the bacterium grows in the absence of oxygen. Growth of the bacteria in, for example, the low-oxygen and slightly acidic environment (the bacteria cannot grow above pH 5) of some canned foods is associated with the production of gas. Canned foods can bulge due to the build-up of the gas. Discarding a bulging unopened can is always a wise precaution. With foodborne botulism, growth of the bacteria in the food may occur, but is not mandatory for developing botulism, as the presence of the toxin alone is sufficient to cause illness. Because the toxin causes the illness, foodborne botulism is often described as a food intoxication.

Rarely, botulism can also be caused by the infection of C. botulinum in an open wound. Growth of the bacteria deep in the tissues leads to the production of the toxin, which then spreads via the bloodstream.

Symptoms of botulism are produced when the toxin enters the bloodstream. The toxin blocks the production of a neurotransmitter called acetylcholine, a chemical that bridges the physical gap between nerve cells and so aids in the transmission of impulses from nerve to nerve. As nerves are affected and paralysis occurs, a person experiences difficulty seeing, talking, and swallowing, and can become nauseous.

C. botulinum is one of a few types of bacteria that can produce a structure known as a spore. A spore is a form of the bacterium that is non-growing but which can persist in that form for a long time and in conditions of excess heat, dryness, and other harsh environments that would kill the normally growing cell. The spore form allows the organism to survive inhospitable conditions and then, when conditions improve, such as in canned food or inside the body, the bacteria can resume growth, division, and toxin production.

WORDS TO KNOW

NEUROTOXIN: A poison that interferes with nerve function, usually by affecting the flow of ions through the cell membrane.

SPORE: A dormant form assumed by some bacteria, such as anthrax, that enable the bacterium to survive high temperatures, dryness, and lack of nourishment for long periods of time. Under proper conditions, the spore may revert to the actively multiplying form of the bacteria.

Scope and Distribution

Botulism is a fairly rare illness. In the United States, for example, only about 100 cases have been reported each year since the 1990s. Most cases are due to the improper canning of foods at home.

The different forms of the botulism toxin display some differences in their geography. In the United States, type A botulism, which is the most severe, occurs most often in western regions, particularly in the Rocky Mountains. Type B toxin, whose symptoms tend to be less severe, is more common in the eastern United States. Type E toxin is found more in the bacteria that live in fresh water sediments. The reasons for their different distributions is not clear.

Treatment and Prevention

Diagnosis of botulism is complicated by the fact that the disease is infrequently seen. A physician may have little experience in dealing with the illness. As well, in its early stages, botulism has symptoms that are similar to other ailments such as Guillain-Barré syndrome and stroke. Both of these considerations sometimes lead to a delayed diagnosis of botulism.

Diagnosis involves the detection of toxin in the infected person's blood, which can be accomplished using specific immune components, or antibodies. An antibody to the specific botulism toxin will react with the toxin, producing a visible clump of material. As well, sometimes living bacteria can be recovered from the feces.

Treatment for botulism often involves the administration of an antibody-containing antitoxin that blocks the binding of the toxin to the nerve cells. With time, paralysis fades. However, recovery can take many weeks. If botulism is suspected soon after exposure to the bacteria, the stomach contents can be emptied to remove potentially contaminated undigested food. When lung muscles have been affected, a patient may need mechanical assistance in breathing.

Impacts and Issues

A century ago, botulism was frequently a death sentence— one of every two people who became ill with it died. In 2007, of the approximately 100 people predicted to become ill with botulism in the United States, eight will die. In contrast to some other diseases that take a toll on the underdeveloped of the world, botulism is more prevalent in developed regions, particularly where food is processed, canned, and sold.

Botulism does have significance in its potential as a bioterrorist threat. This potent killing power of the Clostridium neurotoxins has been recognized for decades. During World War II (1939–1945), several nations including the United States and Canada experimented with the development of botulism toxin-based weapons. Sprays that contained the spore form of C. botulinum were developed and tested. The idea was that inhalation of the spores would lead to resumed growth of the bacteria and production of the lethal neurotoxin. The sprays were never used in battle.

Botulinum toxin A is exploited cosmetically as a means of lessening wrinkles. Injection of Botox relaxes muscles, which can produce a more youthful appearance. The American Society of Aesthetic and Plastic Surgery (ASAPS) estimates that the worldwide market for Botox is around 900 million dollars annually, and over two million Botox procedures are performed per year. Botulinum toxin A has also shown promise in lessening dystonia (muscle spasms) that occurs in cerebral palsy, and in treating crossed eyes (strabismus).

In 1976, a form of botulism was recognized in infants in the United States that stemmed from babies ingesting C. botulinum spores, which colonized their intestinal tract (an infant's intestinal tract is less acidic than that of an adult) and eventually produced botulinum toxin. Evidence indicated that honey was linked with both the reservoir of the bacteria and the resulting disease. Since that time, honey-linked infant botulism has been reported in other countries, prompting recommendations from the American Academy of Pediatrics for all infants less than 12 months of age not to receive foods containing honey.

As botulism is a rare occurrence, The Centers for Disease Control and Prevention (CDC) maintains a central supply of antitoxin against botulism. State health departments consult with the CDC for release of the antitoxin when a case has been reported to them. Fast action is essential, as the antitoxin reduces the severity of the symptoms only if given early.

When a food source of botulism is discovered, the Food and Drug Administration (FDA) issues a class-1 recall of the product. Class-1 recalls are reserved for dangerous or defective products that could cause serious health problems or death, and involve communication between the FDA, manufacturer or supplier, and the public to remove the product from the market, or remove the food source from the food supply. For instance, in February 2007, the FDA issued a warning against consumption of Earth's Best Organic 2 Apple Peach Barley Breakfast baby food because of the risk of contamination with Clostridium botulinum. The manufacturer initiated a recall of the food, and working in conjunction with the FDA, removed the potentially contaminated baby food jars from store shelves, began an awareness campaign, and tracked and corrected the source of the contamination. As of March 2007, a potential outbreak of infant botulism was prevented, and no cases of infant botulism were reported from ingesting Earth's Best Organic baby food.

IN CONTEXT: BOTULINUM TOXIN AS A BIOLOGICAL WEAPON

According to the CDC, aerosolized botulinum toxin is a possible mechanism for a bioterrorism attack. As yet inhalational botulism cannot, however, be clinically differentiated from the naturally occurring forms. What factors might assist or complicate the definitive initial determination of such an attack?

Key clinical or epidemiological factors assisting the determination of an intentional attack:

• Inhalational botulism does not occur naturally.
• Botulism is not transmissible from person-to-person.
• Indications of intentional release of a biologic agent aerosolized botulinum toxin might include an unusual geographic clustering of illness (e.g., persons who attended the same public event or gathering).
• Symptoms begin within six hours to two weeks after exposure (often within 12 to 36 hours).

SOURCE: Centers for Disease Control and Prevention (CDC)

See AlsoBacterial Disease; Food-borne Disease and Food Safety.

BIBLIOGRAPHY

Books

Prescott, Lansing M., John P. Harley, Donald A. Klein. Microbiology. New York: McGraw-Hill, 2004.

Tortora, Gerard J., Berell R. Funke, Christine L. Case. Microbiology: An Introduction. New York: Benjamin Cummings, 2006.

Websites

U.S. Food and Drug Administration. “Clostridium botulinum.” <http://www.cfsan.fda.gov/∼mow/chap2.html> (accessed March 1, 2007).

Brian Hoyle

Botulism

Resources

Botulism is an illness produced by a toxin that is released by the soil bacterium Clostridium botulinum. One type of toxin is also produced by Clostridium baratii. The toxins affect nerves and can produce paralysis. The paralysis can affect the functioning of organs and tissues that are vital to life.

There are three main kinds of botulism. The first is conveyed by food containing the botulism toxin. Contaminated food can produce the illness after being ingested. Growth of the bacteria in the food may occur, but is not necessary for botulism. Just the presence of the toxin is sufficient. Thus, this form of botulism is a food intoxication (as compared with food poisoning, where bacterial growth is necessary). The second way that botulism can be produced is via infection of an open wound with Clostridium botulinum. Growth of the bacteria in the wound leads to the production of the toxin, which can diffuse into the bloodstream. The wound mode of toxin entry is commonly found in intravenous drug abusers. Finally, botulism can occur in young children following the consumption of the organism, typically when hands dirty from outdoor play are put into the mouth.

The latter means of acquiring botulism involves the form of the bacterium known as a spore. A spore is a biologically dormant but environmentally resilient casing around the bacterium’s genetic material. The spore form allows the organism to survive through prolonged periods of inhospitable conditions. When conditions improve, such as when a spore in soil is ingested, resuscitation, growth of the bacterium, and toxin production can resume. For example, foodborne botulism is associated with canned foods where the food was not heated sufficiently prior to canning to kill the spores.

Botulism is relatively rare. In the United States, just over 100 cases are reported each year, on average. The number of cases of foodborne and infant botulism has not changed appreciably through the 1990s to the present day. Foodborne cases have tended to involve the improper preparation of home-canned foods.

There are seven known types of botulism toxin, based on their antigenic make-up. These are designated toxins A through G. Of these, only types A, B, E, and F typically cause botulism in humans, although involvement of type C toxin in infants has been reported, and may be particularly associated with the consumption of contaminated honey.

Infant botulism caused by toxin type C may be different from the other types of botulism in that the toxin is produced in the person following the ingestion of living Clostridium botulinum.

The toxins share similarities in their gross structure and in their mechanism of action. The toxins act by binding to the region of nerve cells that is involved in the release of a chemical known as a neurotransmitter. Neurotransmitters travel across the gap (synapse) separating neurons (nerve cells) and are essential to the continued propagation of a neural impulse. Accordingly, they are vital in maintaining the flow of a transmitted signal from nerve to nerve. Blocking nerve transmissions inhibits the means by which the body can initiate the movement of muscles. The result is paralysis. This paralysis produces a variety of symptoms including double or blurred vision, drooping eyelids, slurred speech, difficulties in swallowing, muscle weakness, paralysis of limbs and respiratory muscles.

The appearance of the symptoms of botulism vary depending on the route of toxin entry. For example, ingestion of toxin-contaminated food usually leads to symptoms within two to three days. However, symptoms can appear sooner or later depending on whether the quantity of toxin ingested is low or high.

The diagnosis of botulism and so the start of the appropriate therapy can be delayed, due to the relative infrequency of the malady and its similarity (in the early stages) with other maladies, such as Guillain-Barre´ syndrome and stroke. Diagnosis can involve the detection of toxin in the patient’s serum, isolation of living bacteria from the feces, or by the ability of the patient’s sample to produce botulism when introduced into test animals.

Clostridium botulinum requires an oxygen-free atmosphere to grow. Growth of the bacteria is associated with the production of gas. Thus, canned foods can display a bulging lid, due to the build-up of internal pressure. Recognition of this phenomenon and discarding of the unopened can is always a safe preventative measure.

Studies conducted by United States health authorities have shown that the different forms of the botulism toxin display some differences in their symptomatology and geographic distribution. Type A associated botulism is most prevalent in the western regions of the US, particularly in the Rocky Mountains. This toxin produces the most severe and long-lasting paralysis. Type B toxin is more common in the eastern regions of the country, especially in the Allegheny mountain range. The paralysis produced by type B toxin is less severe than with type A toxin. Type E botulism toxin is found more in the sediments of fresh water bodies, such as the Great Lakes. Finally, type F is distinctive as it is produced by Clostridium baratii.

Treatment for botulism often involves the administration of an antitoxin, which acts to block the binding of the toxin to the nerve cells. With time, paralysis fades. However, recovery can take a long time. If botulism is suspected soon after exposure to the bacteria, the stomach contents can be pumped out to remove the toxic bacteria, or the wound can be cleaned and disinfected. In cases of respiratory involvement,

KEY TERMS

Antitoxin— A antidote to a toxin that neutralizes its poisonous effects.

Endospore— A small, protective capsule surrounding a bacterium.

Toxin— A poisonous substance.

the patient may need mechanical assistance with breathing until lung function is restored. These measures have reduced the death rate from botulism to 8% from 50% over the past half century.

As dangerous as botulinum toxin is when ingested or when present in the bloodstream, the use of the toxin has been a boon to those seeking non-surgical removal of wrinkles. Intramuscular injection of the so-called “Botox” relaxes muscles and so relieves wrinkles. Thus far, no ill effects of the cosmetic enhancement have appeared. As well, Botox may offer relief to those suffering from the spastic muscle contractions that are a hallmark of cerebral palsy.

See also Poisons and toxins.

Resources

BOOKS

Carruthers, Jean and Alastair Carruthers. Using Botulinum Toxins Cosmetically: A Practical Guide. New York: Taylor & Francis, 2003.

Emmeluth, Donald. Botulism (Deadly Diseases and Epidemics). New York: Chelsea House Publications, 2005.

MacInnis, Peter. Poisons: From Hemlock to Botox and the Killer Bean of Calabar. New York: Arcade Publishing, 2006.

Kathleen Scogna