Botulism E in Wisconsin

What is Botulism E?

Avian botulism is a neuromuscular illness caused by a toxin that is produced by the bacteria Clostridium botulinum. These bacteria typically live in lake, pond or wetland substrates, and sporadically produce toxin when certain environmental conditions develop. In birds, botulism E is a paralytic, often fatal, disease caused by ingestion of the toxin. Affected waterfowl typically show signs of weakness, dizziness, inability to fly, muscular paralysis, and respiratory impairment. While this group of bacteria can produce several types of toxin, wild birds are typically affected by botulism type C (BotC) and botulism typeE (BotE). In Wisconsin, BotC and BotE have both been documented to cause significant waterbird die-offs and also fish kills. BotC usually is associated with waterfowl die-offs on smaller lakes and wetlands, while BotE is known to cause die-offs among fish-eating birds such as common loons and gulls in coastal and Great Lakes ecosystems. Recent history in Wisconsin includes small BotE mortality events documented in 2006, 2007, and 2008 in the Door County, Wisconsin, area of Lake Michigan.

Photo provided by the MI Department of Natural Resources

Why is Botulism E a concern?

Midwest regional reports of BotE are largely confined to the Great Lakes area and primarily involve common loons, gulls, diving ducks, and shorebirds. While BotE has been implicated in waterbird die-offs in the Great Lakes since the 1960’s, in the last decade these mortality events seem to be increasing dramatically in frequency, scale and scope and have been responsible for the deaths of thousands of birds. Botulism E-associated mortality has also been documented in a number of species that are endangered or of special concern, including piping plover and lake sturgeon.

Botulism Surveillance

Beginning in the Fall of 2008, the Wisconsin Department of Natural Resources (DNR) is monitoring waterbird mortality events to identify botulism E outbreaks (and other diseases) along the Wisconsin shores of the Great Lakes. Throughout the later summer and Fall season, when most BotE occurs, DNR staff is conducting active transect surveillance along the shorelines of Door County. Visits will also be made opportunistically to islands in both Green Bay and Lake Michigan to monitor for dead birds and assess the bird populations at risk. In addition, in 2009 DNR researchers will start a study of the impacts of BotE on the Wisconsin breeding populations of common loon.

What should you do if you find dead water birds?

If you encounter dead birds on the Great Lakes shorelines, the DNR urges you to contact the Wisconsin Deadbird Hotline at 1-800- 433-1610. Birds that are found dead in good postmortem condition (no scavenging to the carcass, an intact body cavity, no maggot infestation or strong odor to the carcass) may be eligible for disease investigation by the DNR’s Wildlife Health program. Though BotE only poses a risk to human health through consumption of the bacteria or toxin, precautions should be taken when handling carcasses, including wearing gloves and washing hands. Additionally, pets should be kept away from carcasses. For more information on safety precautions and how to properly dispose of dead water birds on beaches, visit: Guidelines for Handling Birds With Suspected Cases of Botulism [EXIT DNR].

Additional Information

• National Wildlife Health Center [EXIT DNR]
• New York Sea Grant [EXIT DNR]
• Michigan Sea Grant [EXIT DNR]

Questions for Wildlife Management