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Waterfowl Deaths Caused by Avian Cholera


Monday, April 6, 2015

More than 600 waterfowl carcasses discovered at Nelson Lake in Oliver County in March are a result of avian cholera, a bacteria that is readily spread in areas where waterfowl congregate in large numbers.

Dr. Dan Grove, wildlife veterinarian for the North Dakota Game and Fish Department, said the initial inspection on March 10 revealed the presence of primarily mallards and Canada geese, already in varying states of decay. “Based on carcass decomposition, it looked like the onset was likely weeks earlier,” Grove said.

Whole carcasses were shipped March 11 to the National Wildlife Health Center in Madison, Wis., for necropsy and disease testing. The lake was surveyed a second and third time on March 11-12, when carcasses were again collected and shipped.

“Birds were tested for multiple diseases, including avian influenza, which came back negative,” Grove said. “Typically we do not see die-offs in wild birds from AI.”

A midwinter survey in early January had indicated 23,000 mallards and 30,675 geese on Nelson Lake, which serves as the outflow for the Minnkota Power Plant and has open water year-around.

Dead birds on the lake have been reported at some degree over the last several years, Grove said, with several local anglers indicating it is a frequent occurrence.

“This is one of two areas in the state with open water in winter, so waterfowl will congregate in this area,” Grove added. “Whenever large numbers are in a confined area, the chances of a disease outbreak increase.”

Grove encourages anyone seeing dead wildlife in large quantities to report it to the Game and Fish Department. “We are concerned when more than a few deaths are observed in one area within a short period of time,” he said.