Avian botulism is caused by naturally occurring bacteria that produce a toxin under anaerobic, or no oxygen, conditions. The disease paralyzes and often kills birds, especially waterfowl and shorebirds. When birds eat larvae that contain the toxin producing bacteria, a cycle of death begins that can result in hundreds or thousands of birds dying in an outbreak of the disease.

Botulism is most dangerous from July to September, when ducks are molting their feathers and are flightless. Avian botulism outbreaks occur almost every year in North Dakota. Shallow water (18 inches or less) is just one of the conditions in the environment that leads to an outbreak of avian botulism. Also, changes in water level, high temperatures (80° F or above), decaying vegetation, and dead animals in the water.

A bird with avian botulism has drooping eyelids, cannot fly, and even has difficulty swimming, because the disease affects the central nervous system, resulting in paralysis of muscles in the legs, eyelids, and neck. Birds often drown because they cannot hold their heads out of the water.

Long Lake National Wildlife Refuge was established in 1932 to specifically control botulism and produce more ducks. This surrounding region has a long history of botulism. Rainfall is not always high enough to maintain desirable water levels in Long Lake, which is formed in a shallow alkali basin.

We control the problem by using airboats to continually check historic “hot spots” and remove any sick or dead birds. Early detection is important for removing the source of the toxin and slowing the disease cycle.

Between 1941 and 1943, over 250,000 birds are estimated to have died on the Refuge. Hot summers, low water levels, and limited cleanups led to high losses. Research on wildlife diseases, such as botulism, is needed to find the weak link in the disease cycle so that losses can be curtailed or even prevented.

If you see a sick or dying bird, Do Not attempt to help the birds yourself. Please call Refuge or State Game and Fish personnel. Either agency can assist on private land. Although humans are believed to be fairly resistant to the avian botulism toxin, you should avoid contact with sick or dead birds.