(e) = estimate, * = morbidity and mortality

New York State Dept. of Environmental Conservation (NY), Southeastern Cooperative Wildlife Disease Study (SCW), Canadian Cooperative Wildlife Health Center (CCW), USGS National Wildlife Health Center (NW), Wisconsin Dept. of Natural Resources (WI), Minnesota Dept. of Natural Resources (MN), Ohio Division of Wildlife (OH), Missouri Dept. of Conservation (MO).

Written and compiled by Kathryn Converse/Rex Sohn - Western US, Kimberli Miller/Grace McLaughlin - Eastern US, Christine Lemanski, NWHC. The Quarterly Wildlife Mortality Report is available at http://www.nwhc.usgs.gov.To report mortality or receive information about this report, contact the above NWHC staff, or for Hawaiian Islands contact Thierry Work. Phone: (608) 270-2400, FAX: (608) 270-2415 or e-mail: kathy_converse@usgs.gov. USGS National Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711.

Quarterly Mortality Reports

Black-bellied Tree Ducks in Texas
In late July, wildlife biologists in Texas that were conducting a brood rearing study, reported mortality in 18-24 hour old black-bellied tree ducks at La Sal Vieja in Willacy County. Ducklings displayed abnormal behavior within 20 minutes of entering the water from their nests. Clinical signs included lagging behind the brood, swimming in circles, resting their head in the water, head shaking, convulsions, and sudden death. Some adult ducks also exhibited head shaking but only young chicks died. The salinity of La Sal Vieja has increased in recent years due to drought conditions. The salinity was 355 ppt at the time of this mortality. The NWHC detected brain sodium concentrations ranging from 2,440 to 4,050 ppm wet weight in six ducklings. Levels greater than 2,000 parts ppm wet weight are consistent with sodium poisoning. The ducklings had mild to severe hydropic changes in their eye lenses, a change observed in ducklings dying from sodium poisoning in other hypersaline wetlands.

Salmonellosis in a Cattle Egret Colony
Mortality of 750 cattle egrets occurred at a nesting colony near Imperial, California that contained 5,000 birds. Biologists from Sonny Bono Salton Sea NWR reported the wetland is surrounded by intensive irrigated agriculture and is near a large cattle feedlot. Salmonella sp. was isolated by the NWHC from three egrets and the isolates were submitted to the USDA National Veterinary Services Lab for serotyping. This is the seventh mortality event in cattle egrets due to Salmonellosis; six occurred in southern California and one in Texas. An estimated 9,500 cattle egrets have died in these seven events.

Mortality in Colonial Bird Colonies in the Northern Great Plains, mixed species and Causes
Numerous State and Federal wildlife management personnel in North Dakota, South Dakota and Minnesota reported mortality of colonial nesting birds throughout this quarter. Diagnostic investigations of white pelicans, double-crested cormorants, and ring-billed gulls, by the NWHC, South Dakota State University, South Dakota Public Health Lab, and Minnesota Veterinary Diagnostic Lab, confirmed mortality was due to multiple causes including: botulism type C (major cause), emaciation/starvation, salmonellosis, chlamydiosis, West Nile Virus, septicemia due to unidentified Pasteurella sp., and heavy internal parasitism. Unseasonably hot weather was the likely cause of death of a large number of very young-of-the-year white pelicans at Lac Qui Parle Wildlife Management Area in southwestern Minnesota, followed by botulism C mortality in ducks, gulls, and shorebirds. West Nile Virus was isolated from some older pelicans. At another site in Minnesota, a few neurologically impaired pied-billed grebes, pelicans, ducks, and cormorants were noted. Pelicans and grebes tested positive for West Nile virus and negative for botulism type C, while the reverse was true for the other species. A cormorant also tested positive for P. multocida, although lesions associated with avian cholera were not noted. Colonial nesting bird populations increased significantly during the mid to late 1990’s in the northern plains states in response to high water levels and abundant nesting and foraging habitat. Drought conditions have returned the past few years with a resulting decline in available nest sites and food resources that may have increased competition and stress, especially for young of the year and juvenile birds. It remains to be seen if continued mortality events in the colonial nesting bird populations in the near future will result in significant declines in these species in the region.

Botulism type E mortality continues on Lake Erie
Botulism type E mortality continued on Lake Erie throughout this quarter. In July, the NY State Wildlife Pathology Lab and NWHC investigated mortality in a ring-billed gull breeding colony near Lackawanna, NY. Losses were estimated at more than 3000 birds. In late August and early September, the Canadian Wildlife Service (CWS) reported mortality of several thousand freshwater drum (sheepshead) near Port Colborne, Ontario, in northeastern Lake Erie. Simultaneously the CWS reported several hundred double-crested cormorants and ring-billed gulls and lesser numbers of shorebirds were found along the beaches of Long Point National Wildlife Area, Ontario; botulism type E was confirmed by the Canadian Cooperative Wildlife Health Center. With the confirmation of botulism type E again this summer in gulls, cormorants, and other species, biologists are concerned about high losses of loons, mergansers, and fish- and mussel-eating ducks when they reach Lake Erie in late October and early November.

West Nile virus in the United States, 2002
WNV activity in the 2002 season has been high, particularly in the Upper Midwest and the Gulf Coast. The distribution of West Nile virus infections in birds has extended across the continental United States to western Washington. In California, WNV was detected in a human, but the virus has not been found in mosquito pools, wild birds or sentinel chicken flocks. At the end of October, WNV was detected in western Idaho in a horse. Dead bird surveillance throughout the United States and Canada has confirmed over 15,900 WNV positive birds in 42 states and four Canadian provinces. As of November 15, 2002, there are 3619 confirmed/probable human cases of West Nile virus in 41 of the United States and the District of Columbia, with 212 mortalities in 24 states. There have been 13,577 equine cases reported to the USDA, with an estimated 33% case fatality rate. WNV infection has been identified in several non-avian species this season, including a wolf, fox and gray squirrels, domestic dog, reindeer, harbor seal, and alligator. These data are based on regional information on WNV activity available on state Internet Web sites, http://www.aphis.usda.gov/oa/wnv/index.html ( http://www.nwhc.usgs.gov/disease_research/west_nile_virus/index.jsp, and http://www.cdc.gov/ncidod/dvbid/westnile/city_states.htm).

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.