(e) = estimate; * = morbidity and mortality

National Wildlife Health Center (NW); Southeastern Cooperative Wildlife Disease Study(SC); California Department of Fish and Game-Wildlife Investigations Laboratory (CA); Texas Veterinary Medical Diagnostic Laboratory (TVD); Canadian Cooperative Wildlife Health Center (CCW); Minnesota Department of Natural Resources (MN).

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 October through December, 1997. There were 41 reports this quarter.

Many of the botulism mortality events in the western United States and Canada which began this summer ended in late September and October. Several of these events were quite large. At Old Wives Lake in Saskatchewan, the estimated losses were between 500,000 and 1,000,000 water birds; 85% were ducks and coots and of the ducks, 23% were northern pintails and 18% were mallards. There were estimated losses of 50.000 birds at both Pakowki Lake in Alberta and Whitewater Lake in Manitoba. Eighty five thousand waterfowl were picked up by US Fish and Wildlife Service (USFWS) and UT State Division of Wildlife Resources personnel on the northern part of the Great Salt Lake. Overall mortality at this site was estimated at 300,000 birds with the majority being green-winged teal, northern pintails, northern shovelers, mallards and American wigeon.

In addition to these large outbreaks, Botulism type C in fish-eating birds occurred once again at Salton Sea NWR in southern CA. The primary birds affected in this event included gulls, white and brown pelicans, herons and egrets; the total pick-up was about 2250.

The largest reported botulism outbreak in the eastern half of the United states in the past decade occurred during October at Chautauqua NWR in Havana, Illinois. Refuge staff picked up over 7,200 birds. The greatest losses included 3,500 green-winged teal, 1,200 mallards and 600 pintail. The mortality slowed after water was added to the refuge and carcass collection was completed and continued on a daily basis. An estimated 20,000 waterfowl were migrating daily through this refuge and at risk throughout the mortality event.

Two mortality events involving approximately 150 western sandpipers, black skimmers, and a few other shorebirds occurred in July and again in October on Marco Island, Collier County, Florida. The cause of death in these events was poisoning by an organophosphorus compound. Subsequent contaminant analysis of birds from the July event confirmed an unusual combination of very high levels of phorate, diazinon, dimethoate, dursban and malathion in one bird and dursban in another. Western sandpipers are migratory while the black skimmers are resident birds in Florida. Biologists are baffled as to the route of exposure. To date there has been no analysis of stomach contents on birds collected during the second event to confirm these findings. NWHC and the University of Florida, Gainesville received birds from these events.

As in the winter of 1996-97, coots with neurologic clinical signs were detected in late November on DeGray Lake, Arkansas and the presence of vacuolar myelinopathy of the white matter of the brain was confirmed. Despite an incredible amount of field work, diagnostic evaluation and research, the cause of this neurologic disease has not been determined. In late October, mortality of over 100 coots in a population of 1000 from Moore County, North Carolina was reported to NWHC by the USFWS. The site is a man-made 1100 acre lake that is developed as a retirement community. Coots that were necropsied had no lesions of infectious disease and histopathological examination of the brains revealed lesions similar to those found in coots and bald eagles from Arkansas. There was similar mortality in coots at this site in 1995. Brain changes were present at that time but no diagnosis could be made due to autolysis.

More than 300 ring-billed gulls have died in Lorraine county, Ohio since September. Clinical signs include convulsions and swimming in circles. Necropsy findings revealed birds in good body condition with a severe fibrinous hemorrhagic enteritis. To date, bacteriology, Virology, parasitology and toxicology tests have been negative.

In the eastern United States, over 550 snow geese died of avian cholera out of an estimated population of 125,000 at Forney Lake, Iowa. In the Western states, avian cholera mortality occurred at multiple waterfowl wintering sites in California and Texas during December. Sites with the most severe mortality include the Winchester Lakes in Haskell County Texas, state, federal and private lands (South Grasslands) and Los Banos oxidation ponds in Merced County CA, Lake Success in Tulare County CA, and the Salton Sea in Imperial and Riverside Counties California. In Texas, the primary species involved are Canada geese while in California, American coots, ruddy ducks, and white geese are the species comprising the greatest proportion of the pick-ups. By the end of December, 1300 birds had been picked up at Winchester Lakes and about 2500 birds had been found dead at South Grasslands and Los Banos oxidation ponds. Pick-ups at Lake Success totaled about 1800 birds. Cholera mortality at Salton Sea began the end of December and, by the first few days of January, 500 birds had been picked-up. California Deptartment of Fish and Game Wildlife Investigations laboratory confirmed the diagnosis of avian cholera in birds from the South Grasslands, Los Banos oxidation ponds and Lake Success, while NWHC performed necropsies and cultures on birds from Winchester Lakes and Salton Sea.

Along with avian cholera mortality events, mycotoxicosis has been confirmed in Texas waterfowl and sandhill cranes this winter. In Howard County Texas approximately 150 sick and dead cranes were found and lesions of fusariotoxicosis confirmed, while in Eastland County about 150 dead northern pintails and mallards died from aflatoxicosis. The source of the toxins in both cases were unharvested or waste peanuts left in the field. Farmers were informed of the problem and began plowing under peanuts to make them less available to the birds. Mycotoxicosis in the cranes was diagnosed at NWHC and in the waterfowl was confirmed by the TX Veterinary Medical Diagnostic Laboratory.

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.