(e) = estimate; * = morbidity and mortality

Illinois Department of Conservation (IL); National Wildlife Health Center (NW); Southeastern Cooperative Wildlife Disease Study (SC); Wisconsin Department of Natural Resources (WI); California Department of Fish and Game - Wildlife Investigations Laboratory (CFG).

Written and compiled by Gregory Kidd, 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, e-mail: kathy_converse@usgs.gov., or for Hawaiian Islands contact Thierry Work. Phone: (608) 270-2400, FAX: (608) 270-2415 or write USGS National Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711.

Quarterly Mortality Reports

In early January, NWHC received a report of significant mortality in wild migratory birds using the Presa de Silva Dam in the state of Guanajuato in central Mexico. An estimated 20,000 migratory birds including ducks, shorebirds, and wading birds died. Personnel from Mexico's National Water Commission (CNA) initially traveled to the site in mid-December. They speculated most of the mortality occurred in a short time period in late November or early December based on the post mortem condition of carcasses. Mortality continued at a low level until the third week in February when the reservoir, used to store irrigation water, was almost empty and the birds started migrating north. A "hospital" was constructed and people from a local environmental group provided supportive care for sick birds. Many of the hospitalized birds did recover and were released. Chemical analyses performed on sediments and water samples detected endosulfan, a chlorinated pesticide, present in low levels. Endosulfan was also detected in a pooled sample of livers from 20 birds. There is no known agricultural use of this pesticide in the area. In March, NWHC received a sample of pooled livers and gizzards from necropsied birds and type C botulinum toxin was detected in the sample. However, the significance of this finding as a contributory factor in the mortality event remains unknown.

In Sauk and Columbia Counties of Wisconsin, three dead bald eagles and eight moribund bald eagles were found within several miles of the Wisconsin River. Six of the eight sick eagles subsequently died. All of the birds were in good physical condition and had no gross lesions indicative of a particular toxin or infectious agent at necropsy. Microscopic examination of tissues indicated diffuse hepatocellular changes consistent with many types of toxic and/or metabolic insults. Brain lesions were also observed and included changes in blood vessel walls. Numerous tests were undertaken, including tests for infectious diseases, cholinesterase inhibiting compounds, lead, strychnine, cyanide, organochlorines, heavy metals as well as gas chromatography/mass spectrometry scans. All of the tests were negative. Clinical signs in the sick eagles included seizures and muscle tremors. The two that survived received supportive care for a month and were later released.

Storm related mortality was reported from two areas in Arkansas this spring. In the first event, near Eudora in Chicot County, over 300 dead and injured geese were found in a farmer's pasture following a storm with golf ball sized hail. In the second event, near Altus, a storm may have been responsible for the death of geese found dead on top of shrubs as if they had "fallen out of the sky." Necropsy revealed massive internal hemorrhages in both of the cases.

Avian cholera was diagnosed from only five areas this quarter. The largest avian cholera outbreak occurred in the Rainwater Basin Wetland Management District. The Rainwater Basin is area in southeastern Nebraska which covers roughly eighteen counties and its unique topography provides habitat for migrating waterfowl. Avian cholera is endemic in the area and losses in a single year have topped 80,000. This year habitat conditions were drier than they have been in the last two years and water was pumped into several wetlands to provide additional habitat for the birds. A total of 2,112 birds were picked up on twenty-eight different areas of the Basin. At Rita Blanca Lake in Texas, avian cholera and shotgun crippling caused the death of an estimated 200 Canada geese. A mild winter may have helped to alleviate losses by allowing the wintering population of 30-40,000 Canada geese to migrate north early. Three areas in California also reported mortality, the most noteworthy being the San Joaquin NWR which reported the death of 37 Aleutian Canada geese.

Salton Sea NWR, California, reported mortality in wigeon on a freshwater unit of the Refuge. Toxicosis was suspected because Furadan had recently been sprayed on adjacent alfalfa fields. Necropsy revealed gizzards full of an alfalfa-like vegetation. Only one of three wigeon necropsied showed brain cholinesterase depression with subsequent reversal. This pattern can be consistent with exposure to a carbamate pesticide such as Furadan since brain cholinesterase levels can return to normal after death.

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.