Avian botulism kills dozens of ducks at Wisconsin lake
Wisconsin Department of Natural Resources officials say that dozens of ducks found sick or dead at Beaver Dam Lake in Dodge County last month have tested positive for botulism , according to a report in the Wisconsin State Journal.
The outbreak that occurred during mid-August, affected approximately 50 ducks. There have not been anymore carcasses found since last month.
Confirmation testing on the birds was performed by the U.S. Geological Survey National Wildlife Health Center in Madison. The center confirmed on Monday that the ducks tested positive for botulism type C toxin.
According to the USGS National Wildlife Center:
Avian botulism is a paralytic disease caused by ingestion of a toxin produced by the bacteria, Clostridium botulinum. This bacteria is widespread in soil and requires warm temperatures, a protein source and an anaerobic (no oxygen) environment in order to become active and produce toxin. Decomposing vegetation and invertebrates combined with warm temperatures can provide ideal conditions for the botulism bacteria to activate and produce toxin. There are several types of toxin produced by strains of this bacteria; birds are most commonly affected by type C and to a lesser extent type E.
Birds either ingest the toxin directly or may eat invertebrates (e.g. chironomids, fly larvae) containing the toxin. Invertebrates are not affected by the toxin and store it in their body. A cycle develops in a botulism outbreak when fly larvae (maggots), feed on animal carcasses and ingest toxin. Ducks that consume toxin-laden maggots can develop botulism after eating as few as 3 or 4 maggots.
Healthy birds, affected birds, and dead birds in various stages of decay are commonly found in the same area. The toxin affects the nervous system by preventing impulse transmission to muscles. Birds are unable to use their wings and legs normally or control the third eyelid, neck muscles, and other muscles. Birds with paralyzed neck muscles cannot hold their heads up and often drown. Death can also result from water deprivation, electrolyte imbalance, respiratory failure, or predation.