Ducks Died of Fungal Infection

State and federal officials have confirmed that about 2,500 mallard ducks found dead southeast of Burley, died of an acute fungus infection. The official cause of death is acute aspergillosis, a respiratory tract infection caused by a fungus commonly found in soil, dead leaves, moldy grain, compost piles, or in other decaying vegetation. Test results from University of Idaho's Caine Veterinary Teaching Center in Caldwell confirmed the presence of the fungus in tissue samples taken from the ducks this week. The results confirm preliminary diagnoses at two other wildlife health labs in Washington and Wisconsin. The fungus can cause respiratory tract infections in birds that inhale the spores. The most likely source of the spores for these ducks is moldy grain, but no specific site has been found as the source. Waterfowl die-offs are common and many happen in the United States every year. During the past six months, 16 events each involving more than 1,000 birds occurred. Testing for diseases is a routine part of the investigation of waterfowl die-offs. The first dead ducks were found by a hunter Friday, December 8, along Land Creek Springs near Oakley. Idaho Department of Fish and Game was notified, and conservation officers found 10 dead ducks near the spring and along the stream's edge. Officers returned to the area on December 10 to find more than 500 dead ducks. By the end of clean-up operations Thursday morning, the number had grown to about 2,500. Though a small proportion of the duck population in Idaho or the United States, the number of dead birds in this die-off is unusual for Idaho. Officials initially considered it unlikely that avian influenza was the cause of this die-off. Widespread testing of waterfowl in fall of 2006 has not found the highly pathogenic avian influenza strain H5N1 in the United States. Tissue samples from dead birds were not consistent with avian influenza, but as a precaution samples were sent to U.S. Geological Survey's National Wildlife Health Center in Wisconsin for testing. Results from the first group of ducks tested confirmed that they did not have the highly pathogenic avian influenza strain H5N1 that is currently of concern in Asia, Europe, the Middle East and Africa. Results from additional tests are pending. The Idaho Department of Environmental Quality, Department of Agriculture and the U.S. Fish and Wildlife Service helped with the investigation of this outbreak. Hunters are advised not to kill any obviously sick animals, including ducks and other waterfowl.