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(e) = estimate; * = morbidity and mortality
National Wildlife
Health Center (NW); Southeastern Cooperative Wildlife Disease Study
(SC); New York State Departmemt of Environmental Conservation (NY);
California Department of Fish and Game-Wildlife Investigations Laboratory
(CFG); Wisconsin Department of Natural Resources (WI)
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.
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Multiple avian
cholera outbreaks began this quarter in the western United States;
outbreaks were most numerous in California, but a single epizootic
occurring on the Great Salt Lake represented the greatest magnitude
of mortality. In California, outbreaks occurred throughout the length
of the state from Del Norte County in the north to Imperial and
Riverside Counties (Salton Sea) in the south. Approximately 42,000
waterfowl and coots have been collected at these California outbreak
sites. Although snow geese, the waterfowl species typically associated
with avian cholera outbreaks, predominated in some of the pick-ups
at refuges in the Sacramento National Wildlife Refuge (NWR) Complex,
ruddy ducks and American coots were the species most involved in
outbreaks in the northern part of the state and other central valley
sites. Also of note, over 700 Aleutian Canada geese (2% of the population)
died from avian cholera this winter at the San Joaquin River NWR.
The largest
avian cholera event this winter occurred on the south of arm of
the Great Salt Lake where approximately 35,000 birds (primarily
eared grebes and lesser numbers of California gulls) died from this
disease. Avian cholera die-off events occurring on the Great Salt
Lake as well as involving primarily eared grebes are rare. This
is only the third documented avian cholera epizootic on the Great
Salt Lake reported to NWHC. All three of these die-offs have involved
eared grebes; In 1994, an estimated 10,000 eared grebes and 5,000
northern shovelers died from avian cholera and in 1995 1,000 eared
grebes and northern shovelers were involved.
Pathologists
at the USGS National Wildlife Health Center (NWHC) in Madison, Wisconsin
and the Southeastern Cooperative Wildlife Disease Study (SCWDS)
at the University of Georgia have found changes in the brains of
coots, mallard, wigeon and ringed-necked ducks from Woodlake, North
Carolina that are similar to the changes found in the brains of
American coots and bald eagles with vacuolar myelinopathy. The disease
had not previously been documented in species other than American
coots and bald eagles. In addition, bald eagles collected from 4
new locations (near Woodlake, North Carolina; Aiken, South Carolina;
and Strom Thurmond Lake and Lake Juliette, Georgia) and coots from
Aiken, South Carolina appear to also have the same brain disease.
In Arkansas, at least 58 bald eagles and an unknown number of coots
have died from this disease since it was first detected in 1994.
Coot and scaup
mortality due to Leygonimus and Sphaeridiotrema parasites
occurred again this fall on Shawano Lake in Wisconsin. As in previous
dieoffs, Leygonimus was found in the coots in large numbers
and Sphaeridiotrema in the scaup. Approximately 3,000 of
the 3500 birds picked up during the 4 week dieoff were coots.
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.
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U.S. Department of the Interior | U.S. Geological Survey
