Type C botulism confirmed along East Arm of Grand Traverse Bay

The Department of Natural Resources recently diagnosed type C botulism in wild waterfowl along the East Arm of Grand Traverse Bay. During the last week of July, dead mallards were collected and sent to the DNR Wildlife Disease Lab in Lansing, Michigan, for testing, and just recently the lab confirmed the disease.

“As of Aug. 4, approximately two dozen mallards had been found dead from type C botulism,” said DNR wildlife biologist and pathologist Tom Cooley. “All of the mallards were found in the same general area, and we will continue to monitor this location, as well as additional locations, for dead birds.”

Botulism is a condition brought on by ingesting a naturally occurring toxin produced by bacteria found in the bottom sediments of water bodies. Because the water levels in the Great Lakes are higher this year than the past several years, water is currently on mudflats that had been previously exposed, and because the water depth is shallow, the anaerobic conditions necessary for the bacteria to grow are established. In the case of type C botulism, dabbling ducks or other shore birds feeding in the sediment can be susceptible to the die-off.

“This isn’t rare,” said Cooley. “Fortunately, type C botulism is not an immediate risk to humans, although pets, including dogs, could acquire the toxin if they were to eat a dead bird. So at this time, it’s best to keep your dog on a leash.”

In the Great Lakes region, both types C and E botulism are reported annually, although this is the first case of botulism in Michigan this year. It was first identified in 1936 in ducks on Green Bay of Lake Michigan, and outbreaks have continued to occur in ducks and shorebirds whenever conditions are favorable for botulism, with many reports of the disease along both coasts of the Lower Peninsula and on many inland lakes.

“It’s important for us to stop the cycle of botulism once it starts,” said Cooley. “Any dead birds that are on the shoreline need to be picked up and disposed of properly. We don’t want other animals feeding on the carcasses.” When handling dead wildlife, the use of rubber gloves is recommended.

Any dead or dying birds that are found along the south shore of Grand Traverse Bay should be reported to the local Traverse City DNR office at 231-922-5280, ext. 6832. Please provide information on the location, type and number of birds. For more information about botulism, see the Michigan DNR Wildlife Disease Manual at www.michigan.gov/wildlifediseasemanual.

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