It appears that the summer of 2001 did not pass without an outbreak of avian botulism. Avian botulism, a paralytic disease caused by ingestion of a toxin produced by the bacterium Clostridium botulinum, has been a major cause of mortality in migratory birds since the early 1900s, when Type C botulism outbreaks impacted mainly ducks and bottom-feeding waterfowl. During 1999 and 2000, an unprecedented die-off of gulls, loons, and mergansers occurred in Lake Erie and was attributed to Type E botulism.
Several thousand birds were affected on Canadian and U.S. beaches, with gull mortality occurring mainly in the summer to early fall, and loon and merganser mortality concentrating in late fall. All major mortality episodes occurred during or following stormy weather when temperatures decreased. In addition to bird mortalities, sporadic die-offs of mudpuppies (aquatic salamanders) and multiple fish species occurred in the central and eastern basins of Lake Erie from March to late November 2000.
The avian botulism life cycle begins with spores that can be found in the lake sediments, water, and fish. Spores can remain in the ecosystem for extended periods of time, even years, and are quite resistant to temperature extremes and dry conditions. Live fish can carry spores of type E botulism, which typically impacts fish-eating birds like loons and grebes. In the absence of oxygen, with a suitable nutrient source, and under favorable temperature and pH, spores can germinate and vegetative growth of bacterial cells will occur. Type E botulism is so powerful that avian botulism can kill a duck that has eaten as few as four bacteria-infested maggots.
A workshop was held earlier this year in Erie, Pennsylvania for researchers and natural resources agency staff to learn more and network on what is known about the disease, and to strategize to develop procedures in the event of future outbreaks.
Recommendations to follow, developed by Sea Grant, include: