Low water levels, high temperatures, and maggot-infested carcasses are all key factors in the outbreak of botulism. Refuge personnel have been patrolling the lake, picking up and disposing of dead birds. Carcasses are then buried to prevent spread of the disease. Refuge personnel will continue daily patrols to minimize and prevent additional loss of birds. The refuge is allowing water to flow into the lake from Quiver Creek to dilute the toxin and cover exposed mudflats. The weather is also helping with cooler day and night temperatures.
The primary species affected by the disease has been green-winged and blue-winged teal with smaller numbers of northern shoveler.
Refuge Manager Ross Adams said, This is the part of my job that I really hate, not because of the hard and sometimes dirty, smelly work of picking up carcasses, but because of the wasteful loss of this beautiful and valuable resource. Once the Habitat Restoration and Enhancement Project is completed on the lake, we will have control of the water we need to provide optimum habitat for the birds to avoid problems such as botulism. This project should be completed by early next summer.
Dead birds were initially discovered by refuge personnel on September 9, 1998. Refuge personnel began collecting birds and samples have been sent to the national Wildlife Health Center, of the U.S. Geological Survey, in Madison, Wisconsin. Results are pending.
The bacteria (Clostridium botulinum) responsible for this outbreak produces a toxin that when ingested causes avian botulism, type C. The bacteria is commonly found in soils and mud along lakes and rivers. When water levels drop, temperatures rise, and oxygen is no longer present, the bacteria reproduce, generating a toxin. Waterfowl and shorebirds are affected when they ingest toxin while feeding in these areas. The disease can spread quickly when healthy birds feed on maggots on infected carcasses, prompting the extensive efforts to remove dead birds.
Avian botulism can effect any bird species, although it is most often seen in waterfowl and shorebirds. The disease is not always fatal, but smaller species such as teal are generally at greater risk. Birds die when they lose control of muscles enabling them to fly, breathe, and they can drown when they can no longer hold up their heads. Type C or avian botulism is rarely a threat to humans, who are more often affected by type A, B or E , sometimes found in improperly canned food.
The U.S. Fish and Wildlife Service is the principal Federal agency responsible for conserving, protecting and enhancing fish, wildlife and plants and their habitats for the continuing benefit of the American people. The Service manages the 93-million-acre National Wildlife Refuge System which encompasses more than 530 national wildlife refuges, thousands of small wetlands and other special management areas. It also operates 66 national fish hatcheries, 64 fishery resource offices and 78 ecological services field stations. The agency enforces Federal wildlife laws, administers the Endangered Species Act, manages migratory bird populations, restores nationally significant fisheries, conserves and restores wildlife habitat such as wetlands, and helps foreign governments with their conservation efforts. It also oversees the Federal Aid program that distributes hundreds of millions of dollars in excise taxes on fishing and hunting equipment to state fish and wildlife agencies. For further information about the programs and activities of the U.S. Fish and Wildlife Service in the Great Lakes-Big Rivers Region, please visit our home page at: http://midwest.fws.gov
