^A **** = cessation date not available at this time.

^B (e) = estimate, *** = mortality estimate not available at this time.

^C Suspect = diagnosis is not finalized or completed tests were unable to confirm the diagnosis, but field signs and historic patterns indicate the disease; Open = diagnosis is not finalized and tests are on-going; Undetermined = testing is complete or was not pursued and no cause of death was evident; NOS = not otherwise specified.

^D California Animal Health and Food Safety Laboratory Network (CAF), Cornell University (COR), Department of Defense (DoD), Florida Fish and Wildlife Conservation Commission (FL), Maryland Department of Agriculture (MDA), National Wildlife Health Center (NW), No diagnostics pursued (NON), NY State, DEC, Division of Fish, Wildlife & Marine Resources (NY), Other (OT), Sea World of San Diego (SWD), Utah Division of Wildlife Resources (UT), Washington State Disease Laboratory (WA).

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 Buckner.

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

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

Quarterly Mortality Reports

Acanthocephaliasis mortality in Gull-billed terns (California).

Gull-billed terns (Gelochelidon nilotica vanrossemi) were submitted to the National Wildlife Health Center by refuge staff at the San Diego Bay National Wildlife Refuge during the month of May 2013 as a result of a mortality event involving 70 breeding adults and chicks. Clinical signs included head tilt, difficulty breathing, and ataxia. No other birds, including waterfowl, skimmers, or other tern and gull species, using this nesting area appeared affected.

There was no evidence of trauma and birds were in fair body condition with mild to moderate lack of pectoral musculature, suggestive of poor nutritional status. All terns had shrimp-like crustaceans present in the proventriculus and gizzard which were later identified as mole crabs (Emerita analoga), one of the most abundant invertebrates living on sandy beaches along the Pacific coast from Alaska to Baja California. In addition, the birds had moderate to heavy presence of intestinal parasites, identified as the acanthocephalan Profilicollis altmani, within the intestines as well as protruding through the intestinal walls into the abdominal cavity causing associated peritonitis. Brain cholinesterase levels were within normal limits for common terns indicating these birds were not recently exposed to organophosphates or carbamates. Routine bacterial cultures of liver and lung revealed no pathogenic organisms.

Acanthocephalans can infect all vertebrates, with ducks, geese and swans most commonly affected. Epizootic mortality events involving this parasite may occur and usually correspond to food shortages and/or periods of high stress (migration and breeding). Mole crabs are a common intermediate host and can have very high concentrations of the parasite. Contact: Barbara Bodenstein, USGS National Wildlife Health Center, 608-270-2447, bbodenstein@usgs.gov

Suspected carbamate poisoning in songbirds (Wisconsin)

The U.S. Fish and Wildlife Service received reports of more than 60 dead songbirds at a private residence in Juneau County, Wisconsin in mid-April 2013. The primary affected species were fox sparrows (Passerella iliaca; FOSP) and dark-eyed juncos (Junco hyemalis; DEJU). Although there were bird feeders in the yard, the majority of the birds were observed under the resident’s cedar trees. Four specimens (2 DEJU and 2 FOSP) from this event were examined at the USGS National Wildlife Health Center. All four had significant brain cholinesterase inhibition and results from follow-up tests were suggestive of carbamate poisoning as the cause of this mortality event.

Carbamate compounds are found in a variety of pesticides approved for application in agricultural and residential land uses. Although these chemicals are considered short-lived in the environment (lasting days instead of months or years) they have also been associated with wild bird deaths throughout the United States. The toxicity of carbamate compounds is due to their ability to disrupt the nervous system of invertebrates and vertebrates through inhibition of cholinesterase enzymes. Once an area contaminated by a pesticide is identified it is important to not only prevent access of the area by additional birds, but also to pick up and properly dispose of carcasses to prevent secondary toxicity in scavengers. Contact: LeAnn White, USGS National Wildlife Health Center, 608-270-2491, clwhite@usgs.gov

Eustronglyoides mortality in juvenile great egrets (Florida)

The Florida Fish & Wildlife Commission investigated mortality of juvenile great egrets at a large active urban rookery (>1000 birds) in Jacksonville, Florida. Mortality was first reported July 23, 2013 at which time biologists observed 71 great egrets (Ardea alba) and 5 juvenile black-crowned night-herons (Nycticorax nycticorax) dead; sick individuals were on the ground and exhibited uncoordination. None of the adults on-site were affected. According to local residents, the die-off began approximately four weeks earlier and had occurred in previous years following harsh weather.

The USGS National Wildlife Health Center received three freshly dead egrets for evaluation; two were emaciated while the third bird was in good nutritional condition. All three juveniles had evidence of disseminated helminth parasite infection observed at necropsy. Various trematode, nematode, cestode and acanthalocephalan parasites were identified; the most notable being nematodes of the genus Eustrongylides. Similar findings were reported in specimens examined by the Southeastern Cooperative Wildlife Disease Study. Mortality from Eustrongylides sp. infection occurs from penetration of the parasite through the stomach wall resulting in secondary peritonitis. Young wading birds are most commonly affected although infections have also been reported in birds of prey from consuming infected fish, amphibians, or snakes that serve as either secondary intermediate hosts or transport hosts in the parasite’s complex life cycle. Major mortality events attributed to Eustrongylidosis have been reported sporadically in Texas, Louisiana, Florida, Virginia, Delaware, South Carolina and Indiana over the past three decades. Contact: Anne Ballmann, USGS National Wildlife Health Center, 608-270-2445, aballmann@usgs.gov

More information on eustrongylidosis can be found in the Field Guide.

Amphibian mortality surveillance in the northeastern United States

A regional, two-year surveillance project is underway in Maryland, New Jersey, Delaware, Pennsylvania and Virginia to better understand the geographic distribution and cause(s) of juvenile mortality among wild amphibians. Biologist Scott Smith, with the Maryland Department of Natural Resources, is the study coordinator. Other collaborating partners include Towson University (Maryland), Montclair State University (New Jersey), USGS-Patuxent Wildlife Research Center (Maryland), New Jersey Division of Fish and Wildlife, Delaware Division of Fish and Wildlife, Pennsylvania Fish and Boat Commission, Virginia Department of Game and Inland Fisheries, Conserve Wildlife Foundation (New Jersey), and the Smithsonian Conservation Biology Institute (Washington, DC).

The USGS National Wildlife Health Center provides diagnostic evaluation of specimens associated with current or suspected amphibian die-offs at select study sites for the surveillance project. Thus far, ranavirus infections have been identified at 8 of 65 locations (2-Delaware; 6-Maryland) surveyed in 3 states. Evaluation of morbidity and mortality at two additional study sites in New Jersey is pending, as are some non-study sites in Maryland that also reported amphibian die-offs in 2013. Wood frog tadpoles (Rana sylvatica) are most frequently involved in the die-offs which can also include spring peepers (Pseudacris crucifer), green frogs (Rana clamitans), American toads (Bufo americanus), eastern spadefoot toads (Leptobrachium sp.) and/or spotted salamanders (Ambystoma maculatum). Field signs include abnormal swimming behavior, hemorrhages on the ventral surface, swollen appearance, and mass mortality or lack of live amphibians. Mortality estimates range from a few individuals to thousands based on spring 2013 egg mass counts at some sites. Ranavirus-associated mortality among amphibians occurs rapidly, potentially decimating an entire season’s recruits within 1-2 weeks at affected locations. This can be easily missed if sites are only visited once during the spring. Population level impacts at locations with recurrent seasonal mortality can be significant. Contact: Anne Ballmann, USGS National Wildlife Health Center, 608-270-2445, aballmann@usgs.gov