Botulism is a dangerous condition caused by infection with the bacteria Clostridium botulinum. The bacteria releases the botulinum toxin, which is severely damaging to the nerves and muscles. If the condition is not treated, the paralysis can affect the lungs and cause respiratory failure.
A botulism infection may be caused by eating food contaminated with the toxin (food-borne botulism) or an infant may develop the illness if they ingest the bacteria before they are old enough to have the gut flora that prevent production of the toxin (infant botulism). Wound botulism occurs when a wound becomes infected with the bacteria as a result of injecting or sniffing contaminated drugs.
The main treatment approach to botulism is administration of an antitoxin. Antitoxins are antibodies that can block the toxin’s effects on the nervous system. Antitoxin therapy is more effective, the earlier in the disease course it is taken. The antitoxin neutralizes only toxin molecules that have not yet bound to and destroyed nerve endings. The more nerve endings the toxin has already bound to, the less effective the antitoxin is.
Before the antitoxin is administered, a skin sensitivity skin test should be performed to check the patient is not allergic to the antitoxin. The intravenous administration of one 10 ml vial of trivalent botulism antitoxin gives enough type A, B, and E antibodies to start neutralizing the toxin.
The patient’s respiratory vital capacity is closely monitored and a ventilation machine is provided for breathing support, if required
Botulism tends to occur in small outbreaks. Since 1980, infant botulism has been more common in the United States than food-borne botulism. Wound botulism, which was once very rare, is now on the rise due to increasing levels of drug abuse. Untreated cases of botulism are often fatal but with early diagnosis and the necessary supportive care, death can be prevented.
Before 1950, the fatality rate associated with food-borne botulism was 60% to 70%, while currently it is 5% to 10% in developed countries. Patients in some risk groups, such as those older than 60 years, have a higher risk of death. The risk of severe disease and death also depends on the toxin type. Cases caused by type A toxin are more likely to be severe infections than those caused by types B or E. Furthermore, sensitivity to the botulinum toxin varies form person to person.
The fatality rate associated with infant botulism is about 2%. Among infants who are hospitalized, recovery usually takes several weeks, although antitoxin (Baby-BIG/ BIGIV) can significantly decrease this time. The fatality rate associated with wound botulism is dependent on the degree of wound contamination and ranges between 1% and 15%.
Treatment with the botulism antitoxin is not without risk. Nearly 9% of those treated with the antitoxin develop severe allergy or hypersensitivity reactions. Equine antitoxin is rarely used in infant botulism since it may cause lifelong hypersensitivity to equine or horse-derived antigens. People who survive botulism do not become immune to the disease and can become infected with the bacteria again.
Reviewed by Sally Robertson, BSc