(e) = estimate; * = morbidity and mortality

National Wildlife Health Center (NW); Southeastern Cooperative Wildlife Disease Study (SC); California Department of Fish and Game-Wildlife Inveatigations Laboratory (CA); Idaho Fish and Game Department (IFG); Canadian Cooperative Wildlife Health Center (CCW).

Written and compiled by Kathryn Converse, Kimberli Miller, Linda Glaser, and Audra Schrader, National Wildlife Health Center (NWHC). To report mortality or if you would like specific information on these mortalities, contact one of the following NWHC staff: Western US Kathryn Converse; Eastern US--Kimberli Miller; Hawaiian Islands--Thierry Work. Phone (608) 270-2400, FAX (608) 270-2415 or E-mail kathy_converse@usgs.gov. National Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711.

Quarterly Mortality Reports

The following highlights wildlife mortality and morbidity events reported to the National Wildlife Health Center (NWHC) from July through September 1997. There were 33 reports this quarter.

Newcastle disease virus (NDV) has been confirmed from two additional double-crested cormorant nesting colonies in the western U.S. this quarter. Last quarter NDV was diagnosed as the cause of a mortality event in double-crested cormorants at the Salton Sea in southern California. This quarter NDV was diagnosed in a cormorant nesting colony within the Bear River Migratory Bird Refuge on the Great Salt Lake in Utah and a double-crested cormorant nesting colony near the mouth of the Columbia River on the Washington-Oregon border. The 300 nest colonies in Utah had low-level morbidity and mortality while the Columbia River nesting colony did not have any noticeable mortality but fledgling aged juvenile cormorants were observed to have the characteristic neurological signs associated with NDV. NWHC isolated NDV from birds collected at both these sites and the virus isolates from both sites were characterized as mesogenic in poultry by the USDA National Veterinary Services Laboratory in Ames, Iowa. The Salton Sea, Bear River and Columbia River events represent the second outbreak of NDV in double-crested cormorants in the U.S. and the first time the disease has been seen in cormorants west of the Rocky Mountains (the West Coast population of double-crested cormorants). The first documented outbreak of NDV in double-crested cormorants in the U.S. occurred in 1992 in the Midwest and Great Lakes region (the Interior population of double-crested cormorants) and was classified as a velogenic neurotropic virus in poultry.

Avian botulism began or continued at multiple sites in the Central and Pacific Flyways during this quarter. Large scale losses were recorded at Old Wives, Pakowki and Whitewater Lakes in Central Canada as well as the Great Salt Lake in the U.S. Smaller botulism events occurred in California, Nevada, Montana, and North and South Dakota. All these events involved primarily waterfowl, shorebirds, and coots. Unusual botulism type C mortality involving fish-eating birds (white and brown pelicans, gulls, herons, and egrets) occurred again at Salton Sea in southern California. A similar die-off at Salton Sea in 1996 involved more than 14,000 birds while mortality this year was about 2,250. The occurrence of botulism type C in fish-eating birds is unusual and the source of the toxin is unclear. Sick and dead fish were collected from various sites in both years and research on the role of fish in these events is ongoing.

Gull mortality in and around Chicago from late June to mid-July received a lot of public and media attention. Several hundred ring-billed gulls were found sick and dead along roads and public areas from Waukegan (near the Illinois-Wisconsin border) to Calumet Harbor (near the Illinois-Indiana border). Carcasses necropsied at NWHC were all fledglings in poor body condition with no signs of infectious or toxic disease. It is possible that the emaciated condition of the birds resulted from diminished food supplies or an over abundance of fledglings competing for food resources.

More than 12,000 birds, including more than 11,000 coots, on Shawano Lake in northern Wisconsin have died of trematode parasite infections from September 30 to mid-November. Three trematode parasites including Sphaeridiotrema globulus were identified as the cause of the mortality. To date, all coots examined died of the trematode Leyogonimus sp. There are no reports in the literature of this trematode infecting coots in North America.

For additional information please contact Dr. Scott Wright, USGS National Wildlife Health Center - Disease Investigations Branch Chief, at 608-270-2460 or Paul Slota, USGS National Wildlife Health Center - Support Services Branch Chief at 608-270-2420.