^a **** = cessation date not available.

^b (e) = estimate, *** = mortality estimate not available.

^c Suspect diagnosis = diagnosis is not finalized or completed tests were unable to confirm the diagnosis, but field signs and historic patterns indicate the disease.

^d Canadian Cooperative Wildlife Health Centre (CCW), Florida Fish and Wildlife Conservation Commission (FL), Montana Fish, Wildlife and Parks Diagnostic Laboratory (MT), No diagnostics pursued (NON), USGS National Wildlife Health Center (NW), Southeastern Cooperative Wildlife Disease Study (SCW), San Diego Zoo (SDZ), University of Florida (UFL).

Written and compiled by the U.S. Geological Survey National Wildlife Health Center Field Investigations Team members: Anne Ballmann, LeAnn White, Barb Bodenstein, and Jennifer Bradsby.

To report mortality or receive information about this report, please contact the USGS National Wildlife Health Center, 6006 Schroeder Road, Madison , WI 53711

For single animal mortality, nationwide, please contact: Jennifer Bradsby, USGS National Wildlife Health Center Biologist by phone: (608) 270-2443, fax: (608)-270-2415, or email: jbradsby@usgs.gov

Quarterly Mortality Reports

Trematodiasis in lesser scaup (Minnesota)
In April 2011, Minnesota Department of Natural Resources (DNR) began surveying Lake Winnibigoshish for avian mortalities. Biologists observed lesser scaup that were unable to fly and had difficulty diving. Approximately 300 lesser scaup were found dead between April and May on the lake and several were submitted to the US Geological Survey’s National Wildlife Health Center where trematodiasis, specifically Sphaeridiotrema globulus and Cyathocotyle bushiensis, was confirmed. This lake has a history of almost annual parasitism mortalities associated with exotic trematodes (S. globulus, C. bushiensis, Leyogonimus polyoon) since 2007.

The lesions associated with these gastrointestinal parasites include mild to severe ulcerative hemorrhagic enteritis and caseous plaques and mortality is thought to be associated with blood loss and shock. Lesser scaup (Aythya affinis) and American coot (Fulica americana) have consistently been the two most affected species by this disease in the midwestern United States. Increased susceptibility of these species may be a result of their increased rate of exposure to the infective stage due to foraging preferences; these include feeding on mollusks and preferences for deep, open water habitats with emergent vegetation. Another factor in increased susceptibility may be due to dense populations of these species that use infected areas during spring and fall migrations.

Field investigation at Poplar Island Environmental Restoration Site (Maryland)
Wildlife disease specialists and biologists from the US Geological Survey’s National Wildlife Health Center, Maryland Department of Natural Resources, and the U.S. Fish & Wildlife Service teamed up to investigate double-crested cormorant mortality at a rookery site on Poplar Island in Talbot County, Maryland, in June 2011. During the summer 2010, virulent Newcastle disease (vND) and concurrent salmonellosis were detected in young of the year cormorants at this rookery resulting in the death of approximately 84 birds. While juvenile cormorant mortality had not yet exceeded that observed during the previous summer, baseline mortality for this population of 816 active nests was uncertain. Given the high density of domestic poultry in Maryland, resource managers wished to investigate the possibility of vND recurrence in this population. Fresh dead carcasses, as well as several 3-6 week old birds exhibiting lethargy, incoordination, and wing dragging were collected for diagnostic evaluation. In addition, serum and paired oropharyngeal and cloacal swabs were collected non-lethally from a subset of asymptomatic 4-6 week old juveniles for future analysis. No evidence of vND or closely related avian paramyxovirus-1 was detected in the affected birds. Aspergillosis was diagnosed in the cormorants found dead while no infectious diseases were identified among the clinically affected juveniles. Collaborative studies with USDA Wildlife Services and the Minnesota Department of Natural Resources have been initiated this summer (2011) to better understand vND disease ecology in double-crested cormorant populations.

Ranavirus mortality among amphibians and chelonians in the Eastern U.S. (Connecticut, Maryland, Florida)
Ranavirus infections were responsible for mortality events involving several species of frogs and Eastern box turtles extending throughout the Atlantic states between April and June 2011. Ranavirus was previously confirmed in wood frogs and spotted salamanders in Connecticut during 2009, and various frog species in Florida during 2002 and 2006. Box turtle mortality due to ranavirus infection has occurred annually since 2008 in Montgomery County, Maryland, although the disease was first reported in amphibians elsewhere in the state in 2005. Larval and metamorph (tadpoles) stages of amphibians are most susceptible to infection by ranavirus. Ranavirus mortality often involves large numbers of individuals, which are found swimming erratically or floating upside-down in the water, and have reddened ventrums, hemorrhages, and skin ulceration. Clinical signs in box turtles include weakness, lethargy, oral plaques, swollen eyes, thick discharge from the mouth and/or nares, and difficulty breathing. It is thought that infected amphibians may serve as a potential reservoir for sympatric chelonians. Ranavirus infections, mostly involving amphibians, have been confirmed in 28 states nationwide since 1997. Maine, Rhode Island, Maryland, Idaho, and Wyoming account for over 40% of the reported ranavirus mortality events in the NWHC wildlife disease database.