AVIAN BOTULISM

by Joann Sweet, Allstate Resource Management

Avian Botulism is one the most common disease problems of migratory birds and domestic water fowl. Each year many birds die after exposure to a toxin produced by specific bacteria. The two most frequently identified types of Avian Botulism that cause mortality in water fowl are type C, usually associated with ducks and type E, which primarily affects gulls.

Losses in South Florida vary from year to year. More birds are known to have died in Dade and Broward Counties, than in Palm Beach County. The disease has been reported on every continent, except Antarctica. Most occurrences have been reported in the past twenty years. The pattern of outbreaks of type C has traveled east from the Mississippi River. Type E outbreaks in birds are less frequent, and are seen to be confined to the Great Lakes area.

A wide variety of birds and a few mammals are susceptible to type C botulism poisoning. Ducks, geese, swans and shorebirds are most often affected by the disease. Vultures are known to be highly resistant to type C toxin. Humans, dogs and cats are generally resistant to Avian Botulism.

The disease attacks the nervous system of birds, causing muscle paralysis. An early symptom is the birds inability to fly. Subsequently, neck and leg muscles become affected and the birds are forced to propel themselves across the water with their wings. The inability of the bird to hold it’s head erect has given this disease the nickname "Limberneck Disease". Frequently, birds drown as paralysis progresses. Those that do not drown eventually die from respiratory failure.

Avian Botulism is most likely to occur when air and water temperatures are high, when water levels fluctuate, and a suitable medium for bacterial growth is present. The bacteria is widely distributed in organic soils and is highly resistant to adverse environmental conditions. As affected birds die and begin to decay, spores ingested during the life of the animal germinate and the toxin is released. Healthy birds that feed on the carcasses that contain the toxin, or on live maggots on the dead birds, will ultimately catch the disease.

Factors contributing to the development of epidemics are lowered water levels during hot summer months, an abundance of flies and insects in the area and animal carcasses for toxin production. While curing affected birds has been moderately successful with the use of antitoxins, capturing sick birds is difficult and treatment is expensive. Emphasis on the prevention of the disease and immediate control of outbreaks is the key to saving waterfowl populations. Prevention programs should be aimed at prompt carcass removal, stabilization of water levels and effective insect control. Prompt and corrective action can greatly reduce the thousands of birds lost in South Florida annually.

6900 S.W. 21st Court . Building 9 . Davie, FL 33317
(954)382-9766 · FAX (954)382-9770

Copyright · ©2007 · Allstate Resource Management · All Rights Reserved