Acute aspergillosis in mallards at Oahe seep near Pierre, South Dakota

Aspergillosis was diagnosed at the cause of death of 158 mallards (Anas platyrhynchos) in January and February 1985 and 11 mallards in December 1985 near Pierre, SD. Isolation of Aspergillus fumigatus from carcass tissues confirmed the diagnosis. The sex ratio of mallards dead from aspergillosis in January and February 1985 was significantly different from the sex ratio in the local population at that time. The source of the fungus was not determined, but severe weather caused physiologically stressed mallards to feeds on corn stored in open piles on the ground, a likely source of the Aspergillus fungus.