The New York State Department of Environmental Conservation (DEC) is investigating the deaths of waterbirds found along the shores of Lake Ontario in Wayne, Oswego and Jefferson counties since mid-October, the agency announced Friday. Preliminary examination by DEC’s Wildlife Health Unit indicates type E botulism is the likely cause of death. Confirmatory testing will be completed in conjunction with the New York State Department of Health.

Common loon Image/William W Dunmire-NPS
Common loon Image/William W Dunmire-NPS

Similar mortality events have occurred in piscivorous (fish-eating) waterfowl and waterbirds on Lake Ontario since 2002. The mortality events associated with this disease usually occur during the fall and tens of thousands of birds have succumbed to this disease across the Great Lakes. Loons, grebes, gulls and certain duck species are the principle victims during these disease outbreaks. Affected birds typically die from drowning after becoming paralyzed by botulinum toxin in the fish they are eating. The most common fish being consumed is the round goby, an invasive species that accumulates toxin by feeding primarily on invasive mussels on the lake bottom. The toxin is generated by Clostridium botulinum, a bacteria that may grow in decomposing algae and other organic matter in the vicinity of mussel beds.

Dead birds pose a threat to scavenging wildlife because the botulism toxin remains viable in the carcass, and carcasses can provide sites for Clostridium growth and the generation of additional toxin. When feasible, burial of carcasses is encouraged, either on-site or in a landfill. As a general precaution, DEC advises people to use rubber or plastic protective gloves or a plastic bag when handling any sick or dead wildlife.

Hunters and anglers who harvest normal-acting waterfowl and fish do not need to take any special precautions when handling or consuming their harvest. However, birds or fish exhibiting abnormal activity may be sick and should not be consumed as cooking may not destroy the botulism 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 (waterfowl, shorebirds, colonial waterbirds, and others) and to a lesser extent type E (gulls, loons, and others).