The 51st annual Wildlife Disease Association conference will be held from July 28 to Aug. 1, 2002, at Humboldt State University, Arcata, Calif. The focus of this year’s conference is “Preparing for Emerging Diseases.” The conference is sponsored by The College of Natural Resources and Sciences at Humboldt State University, the Institute for Wildlife Studies, and The Wildlife Health Center at the University of California, Davis. For more information and conference contact numbers see http://www.humboldt.edu/~wda/.

Emergence of Chronic Wasting Disease in Wisconsin’s White-Tailed Deer

Chronic wasting disease is a progressively degenerative and ultimately fatal disease in deer and elk. It is associated with accumulation of abnormal prion proteins, which are found primarily in brain and lymphatic tissue. Chronic wasting disease was previously only known to occur in wild deer and elk in Colorado, Wyoming, Nebraska, South Dakota, and Saskatchewan. Since 1999, the Wisconsin Department of Natural Resources has tested more than 1,000 deer for the disease, three of which were found to be CWD positive during the 2001 hunting season. The discovery of these CWD positive represents a major expansion of the range of chronic wasting disease and evokes particular concern because extremely high deer densities in southern Wisconsin may aid rapid transmission of the disease, resulting in significant negative effects on this important wildlife species. Learn more about "Emergence of chronic wasting disease in Wisconsin white-tailed deer: information from the field and preliminary analysis," Mike Samuel, August 1, 9 a.m., or by calling him at 608-270-2441.

Can Black-Footed Ferrets Be Vaccinated Against Plague?

Endangered black-footed ferrets are extremely susceptible to sylvatic plague, a disease that has seriously hampered efforts to re-establish ferrets to their historical range. Researchers have assessed how effective vaccinating ferrets against plague could be by using a recombinant protein vaccine that was developed at the U.S. Army Medical Research Institute of Infectious Diseases. Study results indicate that ferrets can be immunized to plague and survive subsequent infection with the disease. Learn more about “Immunization of black-footed ferrets against sylvatic plague,” presented by Tonie Rocke on July 30 at 2:45 or by calling her at 608-270-2451.

Can an oral bait protect the black-footed ferrets primary food supply – prairie dogs?

Sylvatic plague can have a dramatic effect on prairie dog populations often killing more than 95% of individuals in a colony. Prairie dogs are the main food source of black-footed ferrets and instability of prairie dog populations is having an effect on efforts to reintroduce this highly endangered species back into its native geographic range. USGS has been studying the feasibility of protecting prairie dogs against plague infections with the use of a vaccine-laden eatable bait. If the bait is effective, whole populations of prairie dogs could be vaccinated without having to capture them to administer the vaccine. The promising results of this study have convinced biologists to pursue additional testing. Learn more about the use of an oral bait to protect black-tailed prairie dogs from sylvatic plague,” presented by Jordan Mencher on July 30 at 8:30-8:45 or by calling him at 608-270-2405.

West Nile Virus: An Emerging and Rapidly Spreading Disease of North American Birds

West Nile virus was introduced into New York City in 1999, setting off an outbreak of the disease in local birds, particularly American crows, and was the beginning of a rapidly expanding and often fatal disease in free-ranging wild birds of the United States and Canada. The disease, which is most often spread through the bites of mosquitoes, also affects humans and is occasionally fatal. West Nile virus is now established in the New York City area and has spread throughout the temperate climates of the northeastern U.S. for 3 years despite no continuous mosquito activity in the dormant winter months. In 2001, the disease spread to the southern warmer climates of Florida and other Gulf States where there is a lengthy mosquito season, furthering enhancing the survival of the virus. The virus is continuing to spread, likely because of migrating birds “seeding” the virus in these new locations along the migratory pathway in the Mississippi Flyway. The disease will almost certainly spread throughout North America. Thus far, American crows and blue jays have proved most susceptible to the virus and are experiencing high mortality rates. Nearly 100 species of birds are virus positive, however, including more than 60 free-ranging native bird species. The rapid geographical expansion of West Nile virus in the eastern U.S. and Canada and the rapid increase in infection and death rates in birds during the last 3 years reflect the virulent nature of the introduced virus strain, as well as the emergence of a disease of major significance to North American birds. Learn more about “West Nile virus, an emerging disease of North American birds,” presented by Robert McLean on July 28, 9 a.m., or by calling Paul Slota at 608-270-2420.

Invasive Pathogens: Detections and Risks on National Wildlife Refuges

Last year, in an effort to determine the current extent of invasive species problems on National Wildlife Refuges, as well as to identify potential problems and future needs, USGS researchers began a project to identify invasive plants, fish, birds, mammals and disease-causing organisms on the nation’s refuges. These data will assist refuges and other management agencies in developing management strategies for existing invasive species problems, and contingency plans for possible future problems. Through literature searches and surveys of wildlife disease professionals, researchers developed an initial list of about 45 viruses, fungi, bacteria, and helminths that are potentially invasive species. Through the evaluation of database records of 25,320 submissions to the USGS National Wildlife Health Center from refuges from 1975 to 1999, USGS scientists identified 18 potentially invasive species, only 10 of which were on their initial list. The refuges on which these pathogens occurred have been identified, mapped, and compared with non-refuge sites. Targeted lists of potentially invasive species for which monitoring programs could be developed are being prepared for the refuges. Learn more about “Invasive pathogens: detections on National Wildlife Refuges and potential risks to additional refuges,” Grace McLaughlin, July 29, 2:30 p.m., or by calling her at 608-270-2446.

Hawaiian Green Turtles and Fibropapillomatosis Disease

Past studies of free-ranging green turtles with the disease fibropapillomatosis (FP) have shown that animals become immunosuppressed with increasing severity of disease. Additionally, pilot studies have revealed that some animals that strand with severe FP also have circulating bacteria in their blood stream (bacteremia). To see if in addition to being immunosuppressed, turtles with FP are also bacteremic, USGS researchers and colleagues captured free-ranging green turtles from the Kona coast, Hawaii, where FP is absent and from Kaneohe Bay, Oahu, where the disease is present. Each turtle was given an FP severity score ranging from 0 (non-tumored) to 3 (severely tumored). A fifth category included turtles that were stranded on land. We found that the percent of turtles with blood cultures positive for bacteria increased with severity of FP. These data continue to support the hypothesis that immunosuppression is a sequel to FP rather than a pre-requisite and that debilitated turtles offer a permissive environment for bacterial growth in their bodies. Learn more about “Bacteremia in free-ranging Hawaiian green turtles with fibropapillomatosis,” Thierry Work, July 29, 4 p.m., or by calling him at 808-541-3445.

Bird Kills and Botulism at Salton Sea, California

For the past decade, the Salton Sea in southern California has been the site of massive bird kills involving pelicans and other fish-eating birds. During the summer of 1996, for example, type C avian botulism killed nearly 20,000 birds, nearly half of which were western white pelicans, and more than 1,200 endangered California brown pelicans. Smaller botulism bird die-offs have occurred every year thereafter. Three years ago, the USGS began a comprehensive study to investigate and understand the dynamics of this disease. Researchers discovered that occurrence of active, toxin-producing C. botulinum type C in the sediments around the Salton Sea were higher during winter and spring and that the bacteria were found mostly in agricultural drains and at the river deltas. The presence of toxin-producing bacteria in tilapia, a fish species, varied from year to year and were significantly higher in 2000, a comparatively severe outbreak year, than in 2001, a relatively mild year. Learn more about “The epizootiology of Type-C botulism at the Salton Sea, by Pauline Nol, July 30, July 30, or by calling her (608-270-2489) or coauthor Toni Rocke (608-270-2451).

Do Avicides Increase the Risk of Avian Botulism Outbreaks?

In the prairie pothole region of the United States, blackbirds damage ripening sunflower crops. The avicide 3-chloro-p-toluidine hydrochloride (DRC-1339) has been studied as a way to lethally reduce blackbird predation on crops. Birds that have ingested this avicide die within 1-3 days in or near the wetlands where they roost. There was concern that the decomposing carcasses of these birds could provide an optimal site for the production of avian botulism toxin. Maggots feeding on the carcasses could pick up the toxin and be eaten by untargeted waterbirds, especially waterfowl, causing additional deaths and creating an outbreak of avian botulism. During 2000 and 2001, USGS investigated the role of poisoned blackbird carcasses as a potential source of avian botulism in North Dakota wetlands to learn more about the risks of avian botulism outbreaks from the avicide. There was no indication that blackbird carcasses would increase the likelihood of a botulism outbreak. Learn more about the results of this study, “The risks of avian botulism outbreaks from avicide DRC-1339 in North Dakota wetlands,” Michael Samuel, July 29, 1:30 p.m., or by calling him at 608-270-2441.

How Effective is a Vaccine for Brucellosis?

Brucellosis in Greater Yellowstone bison and elk has caused controversy for years. Brucellosis has been eradicated from cattle in Wyoming, Montana, and Idaho, and all three states are now classified as brucellosis free in terms of livestock. Yet free-ranging elk that use feeding grounds in the Greater Yellowstone area, and bison in Yellowstone and Grand Teton National Parks, still have high serum levels of the disease and are seen as a threat to the state-federal cooperative national brucellosis eradication program. Cattle in eastern Idaho were recently diagnosed with brucellosis, with transmission of the disease apparently from fed elk. The Greater Yellowstone Interagency Brucellosis Committee, formed of state and federal agencies involved in wildlife and livestock management in the three states, is committed to eventual elimination of the disease from wildlife, yet management tools to control or eliminate the disease are limited. Wildlife vaccination is one of the methods now used, but effective wildlife vaccinations depend on the effectiveness of the dose, how the dose is delivered, and safety of non-targeted species. In 199, USGS and research colleagues began to study a brucellosis vaccine in elk All tested elk were free of the disease at capture and before vaccination. Learn more about the results of this study, “Effectiveness of Brucella abortus Strain 19 single calfhood vaccination in elk (Cervus elaphus), Tom Roffe, August 1, 2:30 p.m., or by calling him at 406-994-5789.

Snow Geese as Carriers of Avian Cholera in the Playa Lakes Region

The Playa Lakes region of United States has had a history of avian cholera outbreaks. A new study by USGS and other researchers confirm the suspicion that wild birds are a reservoir for avian cholera, a disease that annually causes the deaths of thousands of waterfowl. Along with other research studies, this work indicates that infection with avian cholera occurs in Ross’s and snow goose populations throughout their yearly cycle. Consequently, even in the absence of disease outbreaks, low-level disease transmission and infection may be occurring in these highly social birds. Learn more about “The role of lesser snow geese as carriers of avian cholera in the Playa Lakes region, Michael Samuel, July 30, 4 p.m., or by calling him at 608-270-22441.

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