Article: Botulism

Botulism (from Latin botulus, "sausage") is a rare but serious paralytic illness caused by a nerve toxin, botulin, that is produced by the bacterium Clostridium botulinum. Botulin is a potent known toxin, blocking nerve function and leading to respiratory and musculoskeletal paralysis.

There are three main kinds of botulism:

• Foodborne botulism is a form of foodborne illness and is caused by eating foods that contain the botulism toxin.
• Wound botulism is caused by toxin produced from a wound infected with Clostridium botulinum, this is, also, the most rare type of botulism.
• Infant botulism is caused by consuming the spores of the botulinum bacteria, which then grow in the intestines and release toxin.

All forms of botulism can be fatal and are considered medical emergencies. Foodborne botulism can be especially dangerous as a public health problem because many people can be poisoned from a single contaminated food source.

In the United States an average of 110 cases of botulism are reported each year. Of these, approximately 25% are foodborne, 72% are infant botulism, and 3% are wound botulism. Outbreaks of foodborne botulism involving two or more persons occur during most years and usually are caused by eating contaminated home-canned foods. The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black tar heroin, especially in California^[1].

Symptoms (foodborne and wound forms)

Classic symptoms of botulism occur between 12-36 hours after consuming the botulinum toxin, but they can occur as early as 6 hours or as late as 10 days. Those symptoms usually include dry mouth, difficulty swallowing, slurred speech, muscle weakness, double vision, vomiting, and severe diarrhea, along with a progressive muscle paralysis. These are all symptoms of the muscle paralysis caused by the bacterial toxin. If untreated, these symptoms may progress to cause paralysis of the arms, legs, trunk, respiratory muscles, and possibly eventual death. In all cases the toxin made by C. botulinum causes illness, not the bacterium itself.

Infant botulism

Infant botulism (First recognized in 1976) is the most common form of the ailment in the United States. The mode of action of this form is through actual infection by germinating spores in the gut of an infant. Infection results in constipation, general weakness, loss of head control and difficulty feeding. Because of these symptoms, infant botulism is often referred to as floppy baby syndrome.

Honey, corn syrup, and other sweeteners are potentially dangerous for infants. This is because the mixture of the non-acidic digestive juices of an infant, the human body temperature, and an anaerobic environment creates an ideal medium for botulinum spores to grow and produce toxin. Botulinum spores are among the few bacteria that survive in honey, but they also are widely present in the environment. While these spores are harmless to adults, because of stomach acidity, an infant's digestive system is not yet developed enough to destroy them, and the spores could potentially cause infant botulism. For this reason, it is advised that neither honey, nor any other sweetener, should be given to children until they are weaned.

The leading explanation for why some infants become infected with C. botulinum is that infants do not yet have sufficient numbers of resident microbiota in their intestines to competitively exclude C. botulinum. Thus, without competition, C. botulinum is able to establish itself in the gut of an infant.

Botulinum toxin

Botulinum toxin blocks the release of acetylcholine from nerve endings thus arresting their function. This toxin is unstable to heating, or on prolonged exposure to oxygen, so poisoning generally occurs from the use of improperly bottled or canned foods: typical instances of botulism would be home-bottled preserves used in salads. An unusual example of botulism occurred in Britain in the exceptionally hot, dry summer of 1976, when river levels dropped so low in some areas that feeding swans accidentally ingested material from anaerobic layers in a river (normally out of their reach), and were struck by botulism symptoms.

Botulinum toxin is also used cosmetically, for example in reducing facial wrinkles or excessive transpiration, and is commercially known as Botox.

Diagnosis

Physicians may consider the diagnosis if the patient's history and physical examination suggest botulism. However, these clues are usually not enough to allow a diagnosis of botulism. Other diseases such as Guillain-Barré syndrome, stroke, and myasthenia gravis can appear similar to botulism, and special tests may be needed to exclude these other conditions. These tests may include a brain scan, cerebrospinal fluid examination, nerve conduction test (electromyography, or EMG), and a Edrophonium Chloride (Tensilon) test for myasthenia gravis. The most direct way to confirm the diagnosis is to demonstrate the botulinum toxin in the patient's serum or stool by injecting serum or stool into mice and looking for signs of botulism. The bacteria can also be isolated from the stool of persons with foodborne and infant botulism.

Treatment

The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a breathing machine for weeks, plus intensive medical and nursing care. After several weeks, the paralysis slowly improves. If diagnosed early, foodborne and wound botulism can be treated with an antitoxin which blocks the action of toxin circulating in the blood. This can prevent patients from worsening, but recovery still takes many weeks. Physicians may try to remove contaminated food still in the gut by inducing vomiting or by using enemas. Wounds should be treated, usually surgically, to remove the source of the toxin-producing bacteria. Good supportive care in a hospital is the mainstay of therapy for all forms of botulism. Currently antitoxin is not routinely given for treatment of infant botulism.

Furthermore each case of botulism is a potential public health emergency in that it is necessary to identify the source of the outbreak and ensure that all persons who have been exposed to the toxin have been identified, and that no contaminated food remains.

Complications

Botulism can result in death due to respiratory failure. However, in the past 50 years, the proportion of patients with botulism who die has fallen from about 50% to 8%. A patient with severe botulism may require a breathing machine as well as intensive medical and nursing care for several months. Patients who survive an episode of botulism poisoning may have fatigue and shortness of breath for years and long-term therapy may be needed to aid their recovery.

Prevention

Commercially canned goods are required to undergo a "botulinum cook" (121°C for 3 minutes) and so rarely cause botulism, there have however been notable exceptions (such as the 1978 Alaskan salmon outbreak). Foodborne botulism has more frequently been from home-canned foods with low acid content, such as asparagus, green beans, beets, and corn. However, outbreaks of botulism have resulted from more unusual sources. In July, 2002, fourteen Alaskans ate muktuk (whale meat) from a beached whale, and eight of them developed symptoms of botulism, two of them requiring mechanical ventilation [1]. Other origins of infection include chopped garlic in oil, chile peppers, tomatoes, improperly handled baked potatoes wrapped in aluminum foil, and home-canned or fermented fish. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods. Oils infused with garlic or herbs should be refrigerated. Potatoes which have been baked while wrapped in aluminum foil should be kept hot until served or refrigerated. Because the botulism toxin is destroyed by high temperatures, persons who eat home-canned foods should consider boiling the food for 10 minutes before eating it to ensure safety. Canned foods may also indicate botulism infestation by characteristic outward bulges which result from the bacteria causing pressure to rise inside the can due to gas produced as a waste product, it would be safest to simply throw such cans away. Because honey, and other sweeteners, can form an ideal medium for botulism growth, infants should not be fed them until they are weaned and their digestive juices become too acidic for the bacteria to grow. Wound botulism can be prevented by promptly seeking medical care for infected wounds and by not using injectable street drugs.