Koyukuk NWR

(e) = estimate, * = morbidity and mortality

Canadian Cooperative Wildlife Health Centre at University of Guelph (CC), DE State Diagnostic Lab (DE), Erie County Health Dept. (EH), University of Florida Laboratory of Wildlife Disease Research (FL), IL Dept. of Natural Resources (IL), MI Dept. of Natural Resources (MI), USGS National Wildlife Health Center (NW), New York State Dept. of Environmental Conservation (NY), Southeastern Cooperative Wildlife Disease Study (SC) and WI Dept. of Natural Resources (WI).

Written and compiled by Kathryn Converse, Kimberli Miller, Grace McLaughlin, Rex Sohn and Audra Schrader, NWHC. The Quarterly Wildlife Mortality Report is also available on the Internet at http://www.nwhc.usgs.gov. To report mortality, or if you would like specific information on these mortalities, contact one of the following NWHC staff: Eastern US - Kimberli Miller; Western US - Kathryn Converse; Hawaiian Islands -- Thierry Work; West Nile Virus - Kathryn Converse. 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.

Quarterly Mortality Reports

Avian Botulism and Related Die-offs on Lake Erie. Wildlife and Park managers began seeing dead birds, mostly gulls, on the north and south shores of Lake Erie in late June 2001. Hundreds of gulls, primarily ring-billed, but also black-backed and herring gulls, have been found dead along the shores. Double-crested cormorants have also been found dead in moderate numbers. Many of the dead birds have tested positive for type E botulinum toxin, and one was positive for type C. Thousands of fish of at least six species, including freshwater drum (sheepshead) and sturgeon, have been found sick and dead. The causes of the die-offs in fish have not been determined, but some are thought to be related to storm events and others to algal blooms. In late October, common loons migrated to the north shore and immediately began dying by the hundreds. In previous years, loons have tested positive for type E botulinum; test results are pending at this time.

Botulism and Predation at Horsehead Lake, ND. In early July, Long Lake National Wildlife Refuge began collecting sick and dead birds on Horsehead Lake, a central North Dakota site with a long history of botulism epizootics. During the initial 5 weeks of the outbreak, mortality was primarily observed in eared grebes, blue-winged teal, pintail and mallards, with fewer numbers of shorebirds and colonial nesting birds found. In mid-August, bird mortality dramatically increased with ring-billed and Franklin's gulls as a significant proportion of the total mortality. Five fresh gull carcasses were submitted to National Wildlife Health Center (NWHC) for diagnostic evaluation. Predation and ante mortem trauma by carnivorous millipedes were noted in some birds on necropsy. All 5 gulls tested positive for avian botulism type C toxin suggesting that the ability to avoid avian, mammalian or insectivorous predators was probably compromised.

Botulism in Puerto Rico. Dead and dying herons and egrets were noted in July 2001, in Arecibo, PR. The area is a roosting site for different species of egrets and other water birds. Signs exhibited by sick birds included difficulty flying, turning head to the rear, general debility, no iris response to light change, paralysis of the nictitating membrane, and sick several days before dying. An estimated 300 birds died during this event. No events of this type had been noted previously. The birds examined tested positive for type C botulinum toxin.

Ring-billed Gull Mortality at Roesler Lake, ND. In mid July, U.S. Fish and Wildlife Service (USFWS), Kulm Wetland Management District Office biologists reported numerous sick and dead juvenile ring-billed gulls on Roesler Lake in south central North Dakota. This site had experienced similar die-offs of gulls in the previous 2 years that were thought to be due to salmonellosis or chlamydiosis, however no definitive diagnosis had been established in those cases. Gull carcasses were submitted to NWHC for diagnostic evaluation. Salmonella was cultured from 1 gull, which was also positive for Chlamydia on the polymerase chain reaction test. Acute pulmonary aspergillosis was diagnosed in 3 other gulls. NWHC Wildlife Disease Specialists conducted a field investigation to learn more about the epidemiology of the event and collect additional diagnostic specimens. Human health risks posed by the gull epizootic were discussed with local medical personnel, USFWS, U.S. Dept. of Agriculture APHIS Veterinary Services, and ND Dept. of Public Health. A joint news release was issued informing the public of preventive actions to take to avoid exposure to potential zoonotic disease agents in and around Roesler Lake. The diagnostic investigation of this event is continuing at NWHC and other veterinary diagnostic facilities.

American White Pelican Mortality at Lacreek NWR, SD. Wildlife managers from Lacreek NWR near Martin, SD reported acute mortality in American white pelican chicks on 2 nesting islands in a Refuge impoundment in late July. Specimens submitted to NWHC had gross lesions suggestive of chlamydiosis. The Refuge staff was immediately notified to limit access to the islands and collect and dispose of all carcasses using appropriate procedures for protection of human health. In early August, NWHC Wildlife Disease Specialists visited the Refuge to conduct an epidemiologic investigation, collect additional specimens for diagnostic evaluation, and consult with Refuge staff on potential disease response procedures to reduce the potential of exposure of the public to zoonotic disease agents. At that time the mortality in young of the year American white pelicans had reached almost 100 percent. The diagnostic investigations are ongoing.

Doves in Florida. The University of Florida reported Eurasian collared dove mortality in the western panhandle of coastal Florida that began in late August may be due to Newcastle Disease Virus. Further laboratory evaluation and pathogenicity testing are underway at the National Veterinary Services Laboratory in Ames, Iowa. Several thousand birds are estimated to have died during this outbreak.

Doves in New York. In late May, New York City residents reported sick rock doves (pigeons) in the vicinity of Central Park. Clinical signs included convulsions, circling and disorientation. It was suspected that bird seed had been poisoned. At least 21 doves succumbed during this event. Birds were submitted to NY State Department of Environmental Conservation Wildlife Pathology Unit for diagnostic evaluation. The most notable gross findings were necrotic lesions in the livers and pale kidneys. Histopathological examination of the liver and kidney showed areas of necrosis associated with crystals. The final diagnosis was poisoning due to ethylene glycol (antifreeze).

Amphibians. Amphibian morbidity and mortality continued throughout this quarter in a variety of life stages, species, locations and types of habitat. Of particular note are two events in wood frogs: a first report of a viral infection in larval wood frogs in an isolated area of Alaska, and a die-off of an estimated 10,000 wood frog larvae at a pond in Rhode Island where there was no previous history of amphibian mortality. Chytrid fungus infections were confirmed for the first time in boreal toads in Utah, for the second year in Pacific tree frogs in San Francisquito Canyon, California, and in a declining population of mountain yellow-legged frogs in the Sierra National Forest in California. This diagnosis in mountain yellow-legged frogs could signal a further population decline in excess of 90% or extirpation of the population in this area. In addition, an estimated 500 mountain yellow-legged frogs died of a presumptive ranavirus infection in Kings Canyon National Park in California; possibly the first large mortality event due to a virus in any species of amphibians in California.

Update - Bald Eagle Mortality in Wisconsin. From late December 2000 to March 2001, the Wisconsin Dept. of Natural Resources reported 13 bald eagles were found sick and dead in the Wisconsin River area in south central Wisconsin. Clinical signs included an inability to fly, incoordination, vomiting, mild to moderate seizuring and easily approached and captured. A variety of diagnoses were found in the birds. There was some evidence on histopathology that at least 2 of the eagles had microscopic changes similar to those seen in a 1994-1995 eagle morbidity and mortality event in the same area in which 16 sick and dead bald eagles were recovered. The cause of the die-off was undetermined. Avian vacuolar myelinopathy was ruled out as a cause of mortality in the 1994-95 and 2000-01 WI eagle mortality events.

West Nile Virus Summary for 2001 The following information on West Nile virus (WNV) is a compilation of direct and website communications with several State Departments of Health, ProMED list serve (http://www.promedmail.org/), USDA Animal Plant Health Inspection Service (APHIS) (http://www.aphis.usda.gov/oa/wnv/index.html) updates on equine cases, and Centers for Disease Control (CDC) Morbidity and Mortality Weekly Report (MMWR) (http://www.cdc.gov/mmwr/mmwr_wk.html) of surveillance data reported by states.

West Nile virus infections rapidly increased in intensity and distribution in the United States throughout 2001. The anticipated shift in the focus of WNV infection from the 12 northeastern states and DC positive in 2000, to additional states occurred in both a southward and westward direction. The presence of WNV in an additional 16 states in 2001 (not in VT in 2001) probably reflects infections distributed during the 2000 fall migration of infected birds to southern states (Map 1). The 2001 spring northern migration of similarly infected birds could have led to infections in more western and northern states. West Nile virus was confirmed for the first time this year in Ontario, Canada. This year the USGS Center for Integration of Natural Disaster Information (CINDI) is working with CDC to map the geographic and temporal spread of WNV across United States. These maps are updated weekly and accessible at http://cindi.usgs.gov/hazard/event/west_nile/west_nile.html.

Wild bird mortality continues to be the most sensitive method for detecting WNV activity, so state and local health departments depend on the testing of dead birds to determine the distribution of WNV. Avian mortality has continued unabated since the initiation of spring transmission on April 30, 2001, with expansion of WNV in birds to 27 states and the District of Columbia (Table 1). The American crow is the most susceptible species with over 4,500 confirmed positive in 2001. Other avian species, in particular birds in the Corvidae family (crows, ravens, jays and magpies), are also susceptible and WNV was confirmed in about 1,500 non-crow species this year. WNV was confirmed in 4323 birds in 2000, and 194 birds in 1999. There is continued concern that WNV poses a risk to threatened or endangered species such as the whooping crane, scrub jay and wood stork. Since 1999, the virus has been detected in over 80 species of birds, including 62 free-ranging species from 28 states, the District of Columbia and Ontario, Canada. In addition WNV was confirmed in 6 wild mammals in 2000.

A cumulative list of avian and mammalian species confirmed positive for WNV is available at http://www.nwhc.usgs.gov/research/west_nile/wnvaffected.html.

In addition to avian mortality, the USDA APHIS reports in 2001 there have been 347 cases (344 confirmed, 3 probable) of WNV infection in horses from 18 States (Table 1). Approximately 22.5% of equine infections reported to USDA to date were fatal or the horse was euthanized. Equine deaths from WNV infections by state are: FL (31), NJ (5), PA (4), CT (3), LA (3), MS (3), GA (2), NY (2), DE (1), IL (1), MA (1), NC (1), TN (1) and VA (1). States with equine cases but no deaths are: AL, KY, MD and RI. In 2000 there were 60 equine cases of WNV with 23 deaths and in 1999 there were 25 cases with five deaths.

The CDC reported 49 human cases of WNV have occurred in NY (12), FL (10), CT (6), MD (6), NJ (7), PA (3), MA (2), GA (1), LA (1), and AL (1) (Table 1). There have been five human mortalities confirmed by CDC in AL, CT, GA, MA and NJ (1 per state). In 2000 there were 21 human cases of WNV with two deaths and in 1999 there were 62 human cases with seven deaths.

The USGS National Wildlife Health Center (NWHC) continues to provide diagnostic support to local, state and Federal agencies such as public health and wildlife organizations by receiving carcasses, tissues or serum to attempt detection of WNV. Active surveillance to detect the geographic expansion of the virus by sampling free-ranging wild birds was ongoing in collaboration with USDA, US Fish and Wildlife Service (USFWS) and several state wildlife agencies in the eastern United States. In 2001, the USGS NWHC began a research effort in collaboration with CDC to investigate the role of migratory birds in disseminating the virus and to investigate pathways for WNV maintenance and transmission. Migratory birds are being sampled for presence of WNV at National Wildlife Refuges, National Parks, and Military facilities from Massachusetts to Florida during spring and fall migrations for 3 years. Experimental research conducted by NWHC has demonstrated direct transmission of WNV between infected and uninfected crows under confined laboratory conditions and oral transmission by feeding infant mice infected with WNV to crows. The efficacy of a commercial killed-virus WNV vaccine is currently being evaluated in crows.

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.