Botulism is caused by ingestion of a large amount of a toxin produced by bacteria naturally occurring in soils, both on terrestrial and aquatic environments. Botulism poisoning is more common in late summer when conditions are most favorable to growth of the bacteria. It is most commonly seen in waterfowl and other aquatic birds, but occasionally occurs in other birds and mammals. Maggots feeding on carcasses concentrate the toxin and serve as a source for other birds that eat them. There are two forms seen in wildlife: Type C toxin is most common in waterfowl, and Type E is more commonly seen in other aquatic birds.
Botulism is caused by the toxin produced by the Clostridium botulinum bacterium.
Animals poisoned with the toxin have paralyzed muscles. “Limberneck” is another name given to the disease, due to paralysis of neck muscles often seen in aquatic birds.
No obvious lesions are seen from botulism.
Blood samples taken from sick or recently dead animals are used to confirm the toxin.
Wildlife Management Significance
Botulism is a major mortality factor in waterfowl in western and northern plains states. In the southeast, including Kentucky, it is less common; however, local die-offs due to botulism poisoning are occasionally seen where resident Canada geese or other waterfowl occur.
Treatment and Control
Waterfowl with low levels of the toxin can recover if removed from the area and given fresh food and water. Antiserums are available, but their effectiveness is questionable and they are generally unfeasible to use on wildlife.
The increase in cases in one area can be controlled if affected carcasses are promptly removed. Insect larvae feeding on affected carcasses concentrate the toxin, and are then fed on by other birds; these birds get much higher doses of the toxin than what would occur otherwise in the environment.
Public Health Implications
Type C botulism in humans is generally not associated with waterfowl; however, in general, basic sanitation should be exercised when handling sick or dead birds. Humans are most susceptible to Type E botulism, and should use extreme caution when handling aquatic birds suspected of being poisoned.