Botulism

Botulism is a paralyzing illness caused by a toxin made by the Clostridium botulinum bacteria. This toxin is among the most poisonous substances known to humans, making botulism potentially fatal if left untreated. Each year, more than 100 cases of botulism are reported in the United States, according to the U.S. Centers for Disease Control and Prevention.

C. botulinum bacteria are often found in soil. They form spores (microscopic, dormant “eggs”) that allow them to remain in an inactive state until they are exposed to conditions that are optimal for them to reproduce and release the toxin, including environments that are oxygen-poor and low in acidity. There are seven types of this toxin, which are designated by the letters A through G. Types A, B, E and F cause illness in people.

Exposure to even small amounts of C. botulinum toxin disrupts nerve function by binding to nerve endings and blocking them from releasing acetylcholine, the neurotransmitter that allows muscles to contract. This leads to paralysis.

People often contract botulism after eating home-canned foods. C. botulinum thrives in environments that contain little oxygen, such as canned foods. Cuts and other wounds infected with C. botulinum can also cause botulism. However, the most common form of botulism is the result of C. botulinum growing in an infant’s intestinal tract after inhaling or ingesting the bacteria’s spores.

All cases of botulism are potentially life-threatening and are considered to be medical emergencies. Botulism is not contagious, although outbreaks of botulism can potentially affect groups of people if they all consume the same contaminated food.

In recent years, there has been growing concern over the possibility of using aerosolized (inhalable) botulism in an act of terrorism. Some political entities in other areas of the world have used C. botulinum to craft weapons for use in bioterrorism. Aerosolized forms of C. botulinum can be fatal when inhaled. The toxins produced by these bacteria are extremely lethal and can be easily produced in a laboratory and readily transported. Various United States agencies are studying the potential of such a threat, as well as ways to help prevent such acts from occurring and preparing emergency response personnel to react quickly and effectively in the case of such an event.

In most cases, exposure to C. botulinum toxin is extremely detrimental to a patient’s health. However, tiny, carefully controlled amounts of purified C. botulinum toxin are sometimes used in a cosmetic procedure to prevent contraction of muscles beneath the skin. This has the effect of reducing the appearance of wrinkles. Purified C. botulinum toxin also may be used to treat certain spastic muscle disorders and excessive sweating.

There are three major types of botulism:

Symptoms of foodborne botulism typically appear within 12 to 36 hours of exposure to contaminated foods. However, symptoms can begin as early as six hours or as late as two weeks after exposure. Infant botulism tends to occur within 18 to 36 hours of exposure. Wound botulism usually causes symptoms about one week after a person is exposed to the bacteria.

Patients typically experience a descending pattern of paralysis. muscle weakness usually first affects the facial muscles and then moves down through the upper arms, lower arms, thighs and calves. As this paralysis proceeds down the body, it paralyzes the breathing muscles. This can result in death unless the patient is put on a breathing machine (ventilator).

Some of the symptoms of botulism in infants may be somewhat different. Affected infants are likely to experience constipation, lethargy and tend to feed poorly. Other symptoms of infant botulism include weak crying and poor muscle tone.

To diagnose botulism, a physician will begin by performing a complete physical examination and compile a thorough medical history of the patient. A physician may also inquire about the patient’s recent eating patterns, any recent wounds or other information that might suggest botulism.

Certain blood tests or stool tests are necessary to definitively diagnose botulism. These tests involve taking samples of a patient’s blood or stool for laboratory analysis. This testing is necessary because the symptoms of botulism may also indicate other illnesses, including certain neurological disorders (e.g., Guillain-Barré syndrome, stroke, myasthenia gravis).

If other disorders are suspected, additional tests may be performed. These tests may include brain scans, spinal fluid examination (spinal tap), nerve conduction velocity tests, electromyography and a Tensilon test (used to diagnose myasthenia gravis).

Prompt treatment is essential to successfully treat botulism. Treatment may vary, depending on the type of botulism experienced. For example, patients with foodborne botulism may be induced to vomit or receive enemas or laxatives to rid the gut of contaminated food. Wound botulism may require surgical treatment to remove the C. botulinum bacteria from the site of infection.

Patients with foodborne or wound botulism are typically treated with certain antitoxins (antibodies that can neutralize toxins). This may reduce the severity of a patient’s symptoms when administered during an early stage of the illness. This drug blocks the action of toxins that circulate in the bloodstream, keeping the toxins from damaging nerves. Generally, antitoxins prevent new damage from occurring but do not reverse damage that already has taken place. In addition, wound botulism may also be treated with antibiotics, although antibiotics are not effective for treating foodborne or infant botulism.

Infant botulism may be treated with botulism immune globulin (BIG), human-derived antibodies that are safer for children than the equine-derived antibodies used to treat adults with botulism. BIG may reduce the duration and severity of infant botulism.

Patients with severe botulism may require hospitalization. If the illness affects breathing ability, patients may require the assistance of a breathing machine (ventilator) for a period of weeks. Some patients may require intravenous (into a vein) fluids, or a feeding tube inserted through the nose.

Most patients with botulism recover, but it can take weeks to months before they feel better. Eventually, paralysis and other symptoms slowly resolve as new nerve endings grow that are capable of releasing the neurotransmitter acetylcholine that is necessary for muscle movement. Patients may experience shortness of breath or fatigue for years after successful treatment of botulism. They may also have continued difficulty speaking or swallowing. Long-term therapy may help such patients to better cope with these difficulties.

Only about 8 percent of botulism cases end in death, according to the U.S. Centers for Disease Control and Prevention (CDC). Fifty years ago, as many of 50 percent of botulism cases were fatal.

The most common type of botulism, infant botulism, may be prevented. Honey and corn syrup sometimes contains spores (microscopic, dormant “eggs”) of C. botulinum bacteria that can cause botulism in infants under the age of 1. As a result, children younger than 1 year should not be given even a small amount of honey or corn syrup. Some experts also urge parents not to feed maple syrup to children younger than the age of 1. People older than 1 year who eat these foods usually are not at risk for infant botulism.

Foodborne botulism may also be prevented. This type of botulism is often the result of improper methods of canning foods at home. People who engage in canning are urged to follow strict hygienic guidelines. During canning, foods should be pressure-cooked at 250 degrees Fahrenheit (121 degrees Celsius) for at least 30 minutes. Foods with low acid content (e.g., asparagus, beets, corn, green beans) pose the highest risk of botulism when canned.

Canned foods are not the only source of foodborne botulism. Other tips for reducing foodborne botulism include:

• Avoid eating preserved food if the container bulges or food smells spoiled. People are urged to avoid purchasing products with containers that are punctured, torn, partially opened or damaged in any way. Frozen products that appear to have been thawed and refrozen also should be avoided.
• Do not eat foods that have passed their use-by or sell-by dates.
• Refrigerate oils infused with garlic or herbs.
• Serve potatoes baked in aluminum foil while still hot, or refrigerate them promptly.
• When possible, boil canned foods for 10 minutes before eating. This will kill any toxins that may be present.

It is also important to thoroughly wash and scrub any can-openers, utensils, containers or counters that have come into contact with potentially contaminated foods. Discard sponges or cloths used in cleanup efforts. Promptly launder any potentially contaminated clothing and wash hands thoroughly. Wound botulism may be prevented if people with wounds promptly clean and treat their wounds and seek appropriate medical care when necessary. Avoiding intravenous drug use can also reduce the risk of botulism associated with wounds.

A vaccine called pentavalent botulinum toxoid is sometimes given to laboratory workers and military troops at risk for a potential C. botulinum bioterrorism attack. Experts typically do not recommend use of this vaccine among the general public.