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.
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.
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.
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.