by Michelle Beaupied
Every year, many ducks are paralyzed or die after being exposed to the toxin produced by botulinum bacterium. Clotridium Botulinum Type C (also referred to as “Limberneck Disease”) is one of the major disease problems of wild migratory ducks. Type C outbreaks are more common in the western states though they also occur in the east. Humans, cats, and dogs are generally not affected by Type C botulism.
Clotridium Botulinum Type C causes paralysis by attacking the nervous system. It is a poisoning rather than an infection. As the disease progresses, different levels of paralysis are observed in ducks. An early indication that a duck has been affected is its inability to fly or dive. Diarrhea may also occur. The legs are the next area where paralysis strikes. Once the legs have become paralyzed, ducks are often observed using their wings to propel themselves across the water. Eyelids droop as the inner eyelid becomes paralyzed and eventually, the neck goes limp. At this point, ducks drown due to the inability to hold their heads above water. Affected ducks that do not drown die of respiratory failure.
Botulism Type C spores exist in lake and pond bottoms and thrive when air temperatures rise and water and oxygen levels drop. A hot dry summer increases the probability of outbreaks. As water levels drop, the bacteria are exposed. The ducks will ingest the bacteria when they feed. They also contract botulism by feeding on invertebrate carcasses that harbor the toxin. The toxin also exists in the live maggots that feed on carcasses. By consuming these maggots, the toxin in turn, poisons the ducks.
The quick removal of carcasses greatly helps to prevent large outbreaks. Carcasses provide an environment in which the toxin continues to produce and in which maggots develop. Ducks suffering from botulism can be saved if properly cared for. The most helpful thing rehabilitators can do for ducks with botulism in its early stage is provide them with fresh water. Antitoxins are also available but are expensive. Regulating water levels and controlling insect populations also help in the prevention of large outbreaks.