Wildlife Health Bulletin #98-03

To: Natural Resource/Conservation Managers
From: Director, USGS National Wildlife Health Center (Bob McLean)
Title: Recurrence of Neurological Disease in Coots in North Carolina and Georgia
Date: December 1998

For the second year in a row, a neurological disease affecting American coots has been confirmed at two sites in Moore County, North Carolina, and Monroe County, Georgia. Scientists from the USGS National Wildlife Health Center in Madison, Wisconsin, and from the Southeastern Cooperative Wildlife Disease Study at the University of Georgia, have identified this as the same disease that has killed numerous American coots and at least 58 bald eagles at several sites in southwest Arkansas since 1994. To date, no bald eagles have been diagnosed with this disease in North Carolina or Georgia. Researchers are investigating these two sites and sites in Arkansas, as well as reports of sick or dead coots and waterfowl at other sites.

Affected birds have erratic flight or are unable to fly, swim tipped to the side or with one or both legs extended, and may be found trying to swim on their backs. The birds stagger and have difficulty walking when on land. They usually appear alert and may be unable to escape when approached. The disease is diagnosed by microscopic observation of spaces in the white matter of very fresh brain tissue from affected birds. Through electron microscopy, it has been determined that the spaces are caused by separation of the myelin layers that surround nerves. Myelin is the protective outer covering of nerves, similar to the insulation covering an electric wire. Disruption of this myelin layer changes the transmission of messages through the central nervous system.

Since 1994, intensive laboratory and field studies by Federal, State, and university scientists have not succeeded in identifying the specific cause of this neurological disease, but they believe it is caused by a naturally occurring or man-made toxin. Tests for toxins known to cause similar diseases in other species have been negative, as have tests for infectious diseases.

Wildlife managers are encouraged to observe flocks of American coots and report any sick or dead coots or other waterfowl with similar behavior to the USGS National Wildlife Health Center at (608) 270-2400. Please keep carcasses chilled, not frozen, while contacting the lab.

WILDLIFE HEALTH ALERTS are distributed to natural resource/conservation agencies to provide and promote information exchange about significant wildlife health threats in their geographic region.