National Wildlife Health Center

...advancing wildlife and ecosystem health

National Wildlife Health Center : A Brief History


While the U.S. Geological Survey celebrated its 125th anniversary, from 1879 to 2004, the USGS National Wildlife Health Center celebrated its 35th anniversary, 1975 to 2010. In honor of these events, the National Wildlife Health Center presents a brief history and a timeline of significant events from its past.

Wildlife health and ecosystem health go hand in hand. The National Wildlife Health Center (NWHC) focuses on issues related to wildlife health, which includes a broad spectrum of concerns that also impact public health and domestic animal health. Established in 1975, the NWHC was the first federal program devoted to addressing wildlife disease problems, including responding to wildlife die-offs, technical assistance in the diagnosis, prevention, and control of disease, as well as disease research.

This timeline presents snapshots of significant events from NWHC's history, as well as issues that we are currently addressing. Many items may have a distinct beginning -- such as when the Center became involved with chronic wasting disease and West Nile virus -- but our involvement and partnerships continue as we work to combat and control these and many other diseases.

Some wildlife diseases are well-known because of their potential effect on humans and other animals, such as West Nile virus, chronic wasting disease, rabies, Lyme disease, and others. While some human diseases, like avian influenza and SARS, are potential wildlife health issues. However, other diseases remain obscure to the general public, but can devastate wildlife populations. Combating wildlife disease emergence and re-emergence are top priorities for the staff at the National Wildlife Health Center (NWHC).

Devastating wildlife die-offs were the impetus for the creation of the National Wildlife Health Laboratory in 1975. Duck plague claimed over 40,000 waterfowl at a South Dakota Wildlife Refuge in January 1973. Avian botulism has killed more than a million birds in localized outbreaks in one year. Avian cholera has killed more than 70,000 birds in just one outbreak. Large-scale frog and tadpole die-offs continue. West Nile virus quickly spread across the continent after it was discovered in New York in 1999.

Fast response to events like these is essential. Investigating and diagnosing the cause is key to preventing future problems. Specialists in wildlife disease have backgrounds in veterinary medicine, pathology, virology, bacteriology, biochemistry, parasitology, microbiology, and wildlife ecology. Laboratories at NWHC reflect these specialties and are the places where researchers try to unlock the mysteries of disease mechanisms in wildlife.

Under the auspices of the U.S. Department of the Interior (DOI), the NWHC began as an U.S. Fish and Wildlife Service laboratory that consolidated existing wildlife disease expertise into a single program, focusing on technical assistance in the diagnosis, prevention and control of disease, as well as on wildlife disease research. In 1996, many Federal Department of Interior biological research laboratories in DOI were transferred to the U.S. Geological Survey, which provided NWHC with new partnering opportunities with other Federal, State, and international agencies that worked with free-ranging wildlife. NWHC maintains an integrated balance between diagnostic investigations and research, and has expanded its expertise from primarily a migratory bird and endangered species disease lab to new areas of disease research and investigation, including health of coral reefs, amphibians, fish and reptiles, and marine mammals.

Historical Timeline



2014

B Sal
Content pending

2013

Snake Fungal Disease
Content pending

2008

White Nose Syndrome
Content pending
Newcastle Disease
Content pending

2007

White Nose Syndrome
Content pending

2005

Avian Influenza
Content pending

2004

Coral Reef Investigations

Characterization of the histopathology and microbiology of white pox and white band diseases of acroporid corals of the U.S. Virgin Islands

Coral reefs in the Caribbean have declined due to an unprecedented combination of natural and human stresses. The most significant loss of corals occurred in the 1970s and 1980s when white band disease devastated stands of Acropora palmata (elkhorn coral) and Acropora cervicornis (staghorn coral), the two primary reef-building species on shallow reefs throughout the region, including in Virgin Islands National Park and Buck Island Reef National Monument. The number and geographic range of coral diseases steadily increased throughout the 1990s and early 2000s . Early research by USGS and the National Park Service has shown that, although there is evidence of limited recovery of the acroporid corals in the U.S. Virgin Islands (USVI), white pox disease is one of the major causes of mortality. By late 2004, white pox had been found only on A. palmata. Very few elkhorn colonies appear to have developed white band, although this disease is commonly found on A. cervicornis. The Acropora spp. are now being considered for listing under the Endangered Species Act. There is an urgent need to learn more about these two diseases and the relationship, if any, between them and human activities such as dumping of sewage.

Classification of coral diseases is chaotic. The etiology and pathogenesis of most coral syndromes are unknown. Common names have been applied to some 29 different syndromes. These syndromes are differentiated by geographic location, host species and color, shape, and behavior of the gross lesions. Some of these syndromes may be different manifestations of the same disease process. Management of the diseases of coral is impractical until the etiologies and pathogeneses are known.

Current and future studies aim to characterize the histopathology of white pox of Acropora palmata and white band disease of Acropora cervicornis of the U.S. Virgin Islands, and determine the usefulness of histopathology data for the diagnosis of these two diseases. If the histopathology of the two syndromes is distinct, the differences could be built into differential diagnostic criteria for the two syndromes, thus forming the basis for a classification of two different diseases. Alternatively, if the histopathology is identical, it may be that the two syndromes are different manifestations of the same disease.

The proposed work would complement an extensive reef monitoring study titled ?Recovery and loss of reef-building corals in National Parks in Florida and the Caribbean? funded by the USGS Natural Resources Preservation Program.

Alaskan Sea Duck Investigation

Contaminants in Molting Long-tailed Ducks and Nesting Common Eiders in the Beaufort Sea, Alaska

Trace elements and organochlorines are widely distributed and may enter arctic marine environments as a result of atmospheric transport or point source releases associated with mining and the use and transport of oil and gas resources. In Alaska, h igh concentrations of selenium were found in spectacled and king eiders and emperor geese, and elevated lead exposure has been reported in spectacled eiders and long-tailed ducks. Persistent organic pollutants have historically received less attention in Alaskan birds than trace elements, although organochlorine concentrations were measured in seabird eggs collected from several nesting areas in the mid-1970s and in eggs of bald eagles from the Aleutian archipelago in the 1990s.

The objectives of this project were to compare contaminant levels in sea ducks using lagoons and barrier islands in the Beaufort Sea near the Prudhoe Bay oil fields with a reference site east of Prudhoe Bay. Trace elements were measured in blood of nesting common eiders and molting long-tailed ducks, and trace elements and organic contaminants in were measured in common eider eggs. The serum activities of five enzymes were compared with selenium concentrations in blood, as an indication of potential selenium-induced liver damage.

Except for selenium (36.1 ?g/g dry weight (dw) in common eiders and 48.8 ?g/g dw in long-tailed ducks), concentrations of trace elements in blood were low. Concentrations of several trace elements in blood differed between the oil field site and the control area, but they were not consistently higher at one location. In long-tailed ducks, the correlation between two serum enzymes and selenium concentrations in blood suggests an adverse effect of selenium on the liver. Although common eiders had high selenium concentrations in their blood, selenium residues in eggs were well below concentrations known to have adverse reproductive effects in other species of birds. Several organochlorine pesticides, polychlorinated biphenyls, and polyaromatic hydrocarbons were found in all eider eggs tested, but at very low concentrations.

Coral Disease Confrence

USGS Programs from Wisconsin Offices Pathogens and Diseases Biological Resources Division

A New Beginning for Coral Health: Developing Diagnostic Criteria

Cooperators: National Oceanic and Atmospheric Administration, the Coral Disease and Health Consortium, the International Registry for Coral Pathology

Project Chief: Lou Sileo

Location: Madison , WI

Marine professionals and diving enthusiasts observed a dramatic increase in coral disease incidents since the mid-1990s, but the nomenclature and study of coral disease remained its infancy. To aid in developing a standardized approach to diagnosing coral disease, the National Wildlife Health Center co-sponsored the Coral Disease and Health Workshop: Developing Diagnostic Criteria in Madison , Wisconsin . This workshop was designed to define and consolidate the existing criteria for diagnosing coral diseases, and to establish a method for developing coral disease nomenclature. Other sponsors were the National Oceanic and Atmospheric Administration, the Coral Disease and Health Consortium, and the International Registry for Coral Pathology.

Workshop organizers targeted 13 unique diseases and syndromes for discussion at the workshop: White Pox, White Band, White Plague, Black Band, Red Band, Red Band II, Bleaching, Aspergillosis, Mechanical Lesions, Growth Disturbances, Yellow Band, Blotch, and Dark Spot Disease. These diseases were chosen not only for the dramatic effects they cause on coral health, but also for the unique challenges they present in diagnoses. Experts on these diseases were asked to present papers which summarized the extent of knowledge about each disease or syndrome. Each disease was the subject of several hours of discussion in individual breakout sessions, from which summaries were presented on the third day of the workshop. These summaries are in final review and will be available on the Coral Disease and Health Workshop Web site, or through the NWHC Web site.

Workshop participants (56) came from across the U.S., and from the U.K. and Israel. Coral experts span many scientific disciplines; participants included biologists, microbiologists, ecologists, pathologists, veterinarians, laboratory specialists, and field specialists. The USGS scientists at NWHC specialize in wildlife disease investigations, for diagnosing disease and understanding disease pathology in wild animals, thus, it was an ideal learning laboratory for coral scientists who need to know more about this process.


2003

Monkeypox in the U.S.

Monkeypox in the U.S.

Monkeypox is a contagious disease casued by a virus related to smallpox. The disease affects a wide variety of mammal species, including humans in Central and West Africa where the disease is endemic. Monkeypox arrived in the U.S. in the spring of 2004 through a shipment of several species of rodents from Africa, some of which were infected with the virus. The virus then spread to prairie dogs through the pet trade. During the next several months 72 suspected human cases of monkeypox were reported in 6 states in association with infected prairie dogs (37 were confirmed). The disease had previously been confined to Africa, where tree squirrels are believed to be the reservoir. Its arrival in the U.S. prompted the USGS to launch a study to determine if the disease had spread from infected pets to local wildlife. If the monkeypox virus had escaped into the wild, it could potentially have found a reservoir in mice, squirrels, or other wildlife populations.

USGS researchers, together with U.S. Department of Agriculture Wildlife Services in Wisconsin and Illinois , investigated wild populations of rodents in areas where cases of monkeypox in humans or pets were reported. In 9 Wisconsin and Illinois locations, scientists trapped 237 animals, representing 14 species, and tested them for monkeypox virus and monkeypox virus specific antibodies; all were negative. Such studies of wildlife populations immediately following the invasion of an exotic pathogen are critical in determining if disease has infected wildlife, where it may become established in reservoir species, potentially infecting human and other wildlife species.


2002

Mysterious Vulture die-off

Mysterious Vulture die-off

The USGS National Wildlife Health Center (NWHC) is collaborating on investigations into the cause for decline of the white-backed vulture in Pakistan . Most of these vultures have died from kidney failure. Residue analysis in wild vultures from Pakistan and toxicity experiments have shown vultures, unlike mammals, to be extremely sensitive to diclofenac, a non-steroidal anti-inflammatory drug, commonly used by veterinarians on agricultural animals in Pakistan.

Small concentrations of this pharmaceutical remaining in the tissue of livestock, which is then scavenged by vultures, results in renal failure. These findings implicate diclofenac as the cause of drastic decline in the white-backed vulture population (90%) in the past 5 years. Vultures are exposed to diclofenac by scavenging agricultural animals that have been treated with diclofenac before death. A paper reporting these findings has been published in the journal Nature.

For more information regarding the vulture die-offs in Pakistan , check out this New York Times article (requires registration) or contact Dr. Carol Meteyer, (608) 270-2462.

NBII node goes online

National Biology Information Infrastructure Goes Online

The National Biological Information Infrastructure (NBII) is a broad, collaborative program to provide increased access to data and information on the nation's biological resources. The National Wildlife Health Center contributed substantial resources toward the development of a Wildlife Disease Information Node.

Nodes are interconnected entry points that, taken together, form the NBII. The establishment of these nodes is helping the NBII provide a vast community of users with rapid access to information on the nation's biological resources.

For more information on the National Wildlife Health Center 's contribution to NBII, visit the Wildlife Disease Node or contact Dr. Joshua Dein, (608) 270-2482

Chronic Wasting Disease in Wisconsin

Exploring the Dynamics of Chronic Wasting Disease

Chronic wasting disease (CWD) is a disease of the nervous system in deer and elk that results in distinctive brain lesions. Extensive media coverage in 2002 resulted in renewed efforts to understand this disease. It continues to be a major issue for wildlife scientists throughout the Nation, and a key focus for research at the USGS National Wildlife Health Center (NWHC). Research is focused on understanding how the disease is transmitted among elk and deer, understanding the patterns of infection, and determining how infection rates differ according to age and sex of the animal. The NWHC is searching for indications of genetic resistance to CWD, as well as developing tools for understanding CWD epidemics. Scientists are also researching the role that infected deer carcasses play in CWD transmission and how feeding and baiting may affect transmission patterns. Further research explores the susceptibility of small mammals and their potential role in the transmission of CWD.

The NWHC continues to investigate CWD in Wisconsin and throughout the Nation. NWHC scientists have provided general information, consultation, and assistance to state agencies. NWHC staff participate in the multi-agency CWD Science and Health Team and the Research Team, providing analyses and advice crucial to determining the distribution of the disease in and around the Midwest. The NWHC has assisted the Wisconsin Department of Natural Resources by providing scientific expertise and guidance in the development of an environmental impact statement for CWD (the first in the Nation), participating in 6 public hearings about CWD held across the state, participating in special state-sponsored deer harvests as a part of disease control programs, and working alongside state employees to collect samples at tissue-processing centers for CWD testing. By participating in all of these tasks, NWHC scientists are able to take ?hands-on? skills to other states agencies and tribes to benefit their CWD programs.

Through collaboration and research, NWHC scientists seek a better understanding of the dynamics of CWD in wild populations as it expands over different landscapes. Scientists at the NWHC are committed to the belief that collaboration with many different agencies is critical to understanding and controlling this disease.

Find out more about how the National Wildlife Health Center is Helping to Combat Chronic Wasting Disease (2,049 kb) or contact Scott Wright or Paul Slota (608) 270-2420 for more information.


2001

Oral vaccine for plague

Plague Immunization in Black-footed Ferrets and Prairie Dogs

Plague is a bacterial disease transmitted by fleas that can afflict numerous species of mammals, including humans. Prairie dogs are one of the most important reservoirs of this disease and they are the primary food source of the endangered black-footed ferret, which is also susceptible to the disease. Sylvatic plague can decimate prairie dog colonies, with mortality rates of 90 percent or more. Because of the susceptibility of prairie dogs to plague, coupled with the potentially devastating effect the disease can have on black-footed ferrets, it is a vital concern for ferret recovery programs.

The USGS National Wildlife Health Center (NWHC), in collaboration with other Federal agencies, began investigating the feasibility of immunizing black-footed ferrets, prairie dogs, and other rodent reservoirs against plague infections. Preliminary results suggest that ferrets can be successfully immunized against plague by injections, thus providing a mechanism for captive-release programs to immunize endangered ferrets.

Immunizing entire populations of free-ranging prairie dogs and other rodents is much more challenging. Nonetheless, preliminary NWHC studies indicate prairie dogs can be successfully immunized by voluntarily feeding on oral vaccine-laden baits. These studies suggest that plague could be managed through oral immunization, which would be especially useful in areas where captive-reared black-footed ferrets are to be released and in National Parks or urban areas, where the potential for human exposure is high.

For more information on plague and black-footed ferrets, prairie dogs, or other rodents, see our fact sheet or contact Tonie Rocke, (608) 270-2451.

Whooping Crane reintroduction program

Whooping Crane Reintroduction Project

Scientists at the USGS National Wildlife Health Center provide technical assistance and diagnostic expertise to several recovery efforts for federally threatened and endangered species. One such project involves the establishment of a second migratory flock of endangered whooping cranes. Captive-raised whooping cranes are being taught to follow an ultra-light aircraft and will be led on a 1200 mile migration rout from Wisconsin to Florida.

Nodes are interconnected entry points that, taken together, form the NBII. The establishment of these nodes is helping the NBII provide a vast community of users with rapid access to information on the nation's biological resources.

For more information contact Kim Miller, (608) 270-2740.


1999

Humpback Chub in CO River

Endangered Humpback Chub Threatened by Exotic Fish Parasite

The Asian fish tapeworm, an exotic parasite, invaded the endangered humpback chub population of the Colorado River and Little Colorado River , in Grand Canyon , and was discovered there by 1990. This parasite causes disease and death in hatchery carp and may retard growth in hatchery-reared roundtail chub. The tapeworm can also harm or destroy the intestinal lining and adversely affect factors within the blood. It was introduced into the U.S. in the 1970s with imported grass carp.

In the late 1990s, the USGS National Wildlife Health Center (NWHC) investigated the extent to which this tapeworm has infected the humpback chub population in the Little Colorado River and its growth and physiological effects on the native chub. Small chub face thermal stress when they are washed from the Little Colorado River (23.5 C) to the colder Colorado River (9.5 C). NWHC research also investigated whether the tapeworm exacerbated these effects.

Studies show that, while older juvenile fish (10 months old, 83 mm long), revealed no negative growth or physiological impacts from tapeworm infection, younger fish (2.5 months old and 22 mm long) were as much as 9 percent shorter in length than control fish. Additionally, when food ration was restricted, infected fish began dying 20 days earlier and at nearly double the rate of the control fish throughout the course of the trial. Infected fish and control fish were equally affected by cold shock experiments.

Additionally, studies at the NWHC have shown that fish can acquire infections by preying upon smaller infected fish. This finding is in contrast with previous work which indicated that fish must eat an infected zooplankton intermediate host. Thus, larger humpback chub that normally have few zooplankton in their diet can still become infected by preying upon smaller infected fish. This evidence of the potential for post-cyclic transmission poses new questions of how infections with this parasite may affect older and larger fish.

These results demonstrate the importance of considering the role of Asian fish tapeworm infections when making management decisions focused on conservation, especially involving the endangered humpback chub. Furthermore, these results provide insight into the potential effects this parasite could have should it invade other ecosystems and fish species.

West Nile virus hits U.S.

Assessing the Effects of WNV throughout North America

Since the detection of West Nile virus (WNV) in 1999 in the New York City area, it has rapidly spread across the continent, with virus activity detected in almost all of the continental United States.

The National Wildlife Health Center (NWHC) quickly contributed to the WNV surveillance effort, offering diagnostic services to state and federal public health agencies, as well as specialized expertise, since 1999. The WNV surveillance program works with state and local public health agencies to monitor birds for the presence of the virus nationwide, while investigating local and regional die-offs potentially due to WNV. The NWHC has received over 8,500 carcasses for testing from 34 States plus the District of Columbia, the Department of Defense, as well as the Department of Interior. These submissions represent over 200 species of birds, mammals, and even amphibians. Of these, 16.6 percent have tested positive for WNV or WNV antibodies.

Surveillance, die-off investigations, and experimental studies conducted by USGS have allowed scientists to explore and understand not only the public health importance of the virus? arrival in the Western Hemisphere, but also its potential effect in wild bird populations.

For more information, download our most recent information sheet on WNV (1.39 MB), or contact Emi Saito, 608-270-2400.

Chlamydiosis in Montana Ducks

Chlamydiosis in Montana Ducks

Chlamydiosis is a disease affecting avians that can occasionally be passed to humans. The disease occurs infrequently, and it is rarely reported. However, in 1999, Montana ducks began dying from chlamydiosis in record numbers. Before the crisis was over, the die-off would be, historically, the largest chlamydiosis die-off in North America.

USGS National Wildlife Health Center scientists worked closely in the field with refuge managers to contain this disease, and our labs were critical in identifying several disease factors.

For more information contact Chris Franson, (608)-270-2400.

Avian Botulism model developed

Avian Botulism model developed

In 1996, California saw the largest brown pelican die-off in state history when 1,400 brown pelicans died at the Salton Sea . USGS National Wildlife Health Center scientists were called in to investigate. After nearly three years of research spanning the continent, NWHC developed a model for the disease, immeasurably helping scientists better understand the outbreaks.

For more information, contact Tonie Rocke, (608)-270-2400. Plus, check out NWHC's avian botulism site online.

Amphibian Disease Investigations

Diseases and Malformations of Amphibians in the U.S.

In the early- to mid-1990s, the National Wildlife Health Center (NWHC) began working on finding the causes of the four D?s in amphibians worldwide: deformities, die-offs, diseases, and declines. NWHC has examined over 100 different species of amphibians from National Parks, private lands, and 26 different National Wildlife Refuges. The National Wildlife Refuges have been one of the major sources providing deformed or malformed amphibians for study.

One project, done in collaboration with the Fish and Wildlife Service (FWS), involves investigating malformations in frogs and toads. Many of the deformed amphibians have extra toes, limbs and vertebra, but about an equal number of abnormal frogs and toads have missing extremities and/or eyes. We are investigating each amphibian to determine the cause of the deformity. At least four major causes of amphibian malformations have been identified to date: injuries from predators, a specific minute parasite (fluke), nutritional deficiencies, and contaminants. Over 700 deformed frogs and toads of 18 different species have been captured by FWS biologists and examined carefully in NWHC laboratories. Many bone abnormalities are not visible in live animals, so NWHC scientists take photographs and X-rays to detect and interpret hidden malformations. These unapparent or cryptic malformations often affect the hip joints and spine.

Another ongoing project is nationwide health monitoring of amphibians. Every year, this health screening of amphibians results in the submission of hundreds of eggs, larval and adult salamanders, frogs and toads from all over the country. New diseases have been discovered in recent months and well-known diseases are found in new locations each year. In order to more rapidly identify these diseases, new molecular techniques are being developed. The results of the tests give researchers a better idea of how to contain and manage declining amphibian populations and the diseases.

For more information, check our fact sheet or contact Gail Moede, (608) 270-2438.


1998

CAFO?s: What?s the big stink?

Concentrated Animal Feeding Operations:What?s the Big Stink?

The livestock industry has changed significantly, beginning in the early 1980s, moving towards fewer but larger farms that emphasize intense production and specialization. If these large farms meet certain criteria outlined by the U.S. Environmental Protection Agency (USEPA) they may be designated as Concentrated Animal Feeding Operations (CAFOs). In the U.S., CAFOs annually produce about three times more raw excreted waste than is generated by all humans in the U.S. combined. Under the Clean Water Act, CAFOs must prevent their waste from contaminating surface waters in the surrounding environment. Unlike human waste, which is processed through sanitary treatment facilities, animal waste is typically disposed of through land application or held for remediation in containment lagoons and constructed wetlands. As wetlands created for CAFO waste management purposes also provide habitat for wildlife, the potential for transmission of waste-derived pathogens from domestic to wild animals must be considered.

NWHC completed two studies in the late 1990s that characterized bacterial contaminants in environmental samples obtained from National Wildlife Refuges adjacent to CAFOs in Nebraska and Oklahoma. Samples were collected from the sites in the spring, summer, and early fall. These samples were analyzed for the presence of known bacterial pathogens of wildlife and bacterial indicators of fecal pollution. Additionally, bacterial isolates were tested to determine if they were resistant to antibiotics used in both human and veterinary medicine. Salmonella, a potential wildlife pathogen, was frequently isolated from samples obtained from both study sites. Also, fecal indicator bacteria often exceeded USEPA standards for human recreational bathing waters within the refuges, and these bacteria were often resistant to antibiotics commonly administered to livestock.

As bacterial pathogens with the potential to impact the quality of surrounding environments were present at both study sites, these data highlight the need to monitor CAFO waste disposal practices. Wild animals are often early indicators of problems within the environment, and the effects of CAFO waste disposal practices on wildlife health are not well characterized. Further, standards defining levels of microbial contamination in the environment above which wildlife health may be impacted do not exist. Thus, continued monitoring of CAFO waste disposal practices along with surveillance for wildlife mortality in the vicinity of CAFOs plays an important role in the stewardship of our natural resources.


1997

Reports of Amphibian Malformations

Reports of Amphibian Malformations

When reports of amphibian population declines and frog malformations began to surface in the mid-1990's, citizens and scientists alike became understandably concerned. To respond to these concerns, the USGS National Wildlife Health Center acted quickly to expand the diagnostic capabilities and field investigation methods available to accommodate these new amphibian developments.

NWHC scientists found that the malformations were the result of environmental factors affecting frog developments during early tadpole stages. However, the variations in malformations between sites suggested multiple causes to this problem.

For more information, check out our Amphibian Malformations fact sheet (719 kb) or contact Carol U. Meteyer, (608)-270-2462.


1996

Salton Sea die-offs

Outbreaks of Type C Botulism at the Salton Sea

In 1996, nearly 20,000 pelicans and other fish-eating birds at the Salton Sea became sick or died during a large outbreak of type C avian botulism. The American White Pelican was the species most afflicted, with losses of about 9,000 birds. Over 2,000 endangered California Brown Pelicans were also affected, although more than 500 of these were taken to rehabilitation centers, treated, and ultimately released. Sixty other avian species, totaling nearly 4,500 birds, were found dead during this outbreak. This outbreak resulted in the largest die-off of pelicans ever reported from any cause, and agencies spent over half a million dollars on carcass collection and rehabilitation efforts. Although avian botulism frequently affects waterfowl and shorebirds, primarily in the West, these Salton Sea outbreaks are unique in that they involve pelicans and other fish-eating birds.

Scientists at the USGS National Wildlife Health Center conducted research to determine the role of fish in the epizootiology of botulism at the Salton Sea . Fish, specifically tilapia, were suspected to be the source of toxin for the birds, although a review of the literature failed to reveal a previously established association between fish and type C botulism in birds. Numerous sick and dead tilapia collected at the Sea during the 1996 outbreak were found to contain toxin, including fish remains in dead birds.

The epizootiology of avian botulism in fish-eating birds at the Salton Sea is unique and appears to be closely tied to tilapia, an introduced fish species exotic to North America . Using novel molecular assays developed for this project, researchers determined that live fish routinely harbor type C toxin-producing bacterial cells in their gastrointestinal tracts, and the prevalence of the bacteria in fish varies between years. During the years of our study (1999?2001), live fish were as likely to harbor toxin-producing cells as sick or freshly dead fish. Also, prevalence of the cells in fish reflected the levels of disease occurrence in pelicans during these years.

Based on these and others? findings, we hypothesize that tilapia ingest spores or cells of the botulism bacteria during the winter and spring. During the summer months, the fish are stressed by anoxia and high temperatures and very little material is found in their gut. This static condition of their gastrointestinal tract is ideal for bacterial growth and the production of type C botulism toxin. Furthermore, the fish tend to congregate in the deltas and around the perimeter of the Sea during summer months because of anoxic conditions in the center of the Sea. This makes them easy targets for pelicans and other fish-eating birds. The feeding behavior of pelicans may also make these birds particularly susceptible to botulism. Pelicans swallow fish whole which may remain in their gullet for some period of time; it is not uncommon for several fish carcasses to be regurgitated upon capture of a pelican. Since many of the fish harbor active, toxin-producing bacterial cells at the time of ingestion, botulinum toxin production could increase significantly before digestion.

One of the goals of the Salton Sea restoration project is to provide a safe environment for birds and other inhabitants. Thus, understanding the ecology of avian botulism at the Sea, including the role of fish and environmental stressors, is critical to restoration efforts.


1994

Avian Vacuolar Myelinopathy

Avian Vacuolar Myelinopathy

When 29 bald eagles were found dead in late 1994 at De Gray Lake in Arkansas, scientists at the USGS National Wildlife Health Center were called to investigate. They found that these birds were affected by a mysterious neurological disease, causing them to display severely uncoordinated flight and appear intoxicated. Eagles were observed crashing into rock walls; water birds were seen trailing a wing or leg while swimming, or even lying on their backs in water.

Pathologists at the Center were the first to identify the microscopic brain lesions in birds afflicted with this disease in 1994. Identifying these lesions was critical to determining that the disease occurred in several avian species, not just eagles and coots. Scientists coined the disease Avian vacuolar mylenopathy. Avian vacuolar myelinopathy (AVM) is neurological disease affecting waterbirds, primarily bald eagles and American coots, in the southern U.S. At least 80 bald eagles and possibly thousands of American coots have died from AVM since it was discovered DeGray Lake. AVM has also been confirmed as the cause of death in mallards, buffleheads, ring-necked ducks, Canada geese, killdeer, and a great horned owl.

Birds affected with AVM lack muscle coordination and therefore have difficulty flying and swimming. Birds that died from AVM generally appeared to be in good health with the exception of a characteristic lesion in the myelin of the brain and spinal cord. Thorough necropsy and diagnostic laboratory studies at the USGS National Wildlife Health Center (NWHC) produced no evidence of parasitic, viral, bacterial, or prion infections. Natural or man-made toxins are suspected as the most likely cause of AVM based on histopathological findings. A sentinel study demonstrated that exposure to the agent that causes AVM is site-specific, seasonal, and relatively short in duration. Feeding trials performed at the NWHC with plant material collected from one of the lakes during an outbreak demonstrated that the causative agent of AVM is associated with submersed aquatic vegetation and that the onset of AVM is dose-dependent.

The future of our collaborative research with the Southeastern Cooperative Wildlife Disease Study, U.S. Fish and Wildlife Service, and Wright State University has three objectives. Our first objective is to continue to monitor AVM at the lakes where the disease occurs and at nearby lakes without disease. Our second objective is to characterize the environmental factors at the sites where AVM has occurred. These site characterizations will be instrumental for developing risk assessment models and may generate hypotheses regarding environmental conditions conducive for AVM outbreaks. Our third objective is to identify the causative agent of AVM.

To learn more about AVM, download our information sheet (3.59 mb) or contact Tonie Rocke, (608)-270-2451.


1992

California Sea Otter Study

California Sea Otter Study

From 1992 to 1998, USGS National Wildlife Health Center scientists collaborated with several organizations to study southern sea otter mortality. The results were alarming. More than 40 percent of the animals died from parasitic, fungal, or bacterial infections, an unusual finding both in terms of frequency and variety for wildlife species.

The southern sea otter has been on the U.S. Fish and Wildlife Service's list of 'threatened' wildlife since 1977. Despite their threatened status the population declined substantially between 1995 and 2001. Scientists are still working to better understand this high mortality rate.

For more information, download our Sea Otter Mortality information sheet (397 kb), or contact Paul Slota, (608) 270-2400.

Honolulu field station established

Honolulu Field Station: Science for the Islands

Hawaii is one of the most isolated land masses on Earth. This isolation allowed the evolution of a unique fauna and flora which adapted to an ecosystem with few parasites or predators. Human colonization of the archipelago introduced many foreign plants, animals, and micro-organisms that often outcompeted native fauna and flora. This led to the present situation where non-native plants are overwhelming native vegetation, and introduced predators and disease cause problems for native animals. Hawaii now has the highest per-capita number of endangered species in the U.S. In spite of these problems, the Hawaiian archipelago, which spans 1,500 km, still harbors unique terrestrial, marine, and estuarine wildlife.

The Honolulu Field Station (HFS) of the USGS National Wildlife Health Center was established in 1992 to assist natural resource agencies with wildlife health and disease-related issues in Hawaii and other Pacific Trust Territories. Scientists work with many organizations to assess the effects of natural and man-made diseases in populations of free-ranging wildlife. Using a combination of technical assistance and applied research, wildlife scientists help resource managers identify, manage, and minimize mortality factors in wildlife.

Significant projects at the HFS include research into the causes and ecology of Green Turtle Fibropapillomatosis, and investigating potentially invasive diseases of marine organisms such as marine mammals, reef fish, and invertebrates. The HFS is also collaborating with the State of Hawaii and other institutions to assess health of coral reefs in Hawaii and elsewhere in the Pacific.

For more information, visit the Hawaii Field Station online, or contact Thierry M. Work, 808-541-3445.


1991

Ban on Lead Shot

Ban on Lead Shot for Hunting Waterfowl

An exhaustive National Wildlife Health Center study provided the data needed to implement laws prohibiting the use of toxic lead shot in the U.S. , saving dozens of bald eagles from lead poisoning.

The Fish and Wildlife Service made efforts to understand the connection between lead poisoning and the use of lead shot for hunting as early as the 1930's. But there were difficulties in trying to understand these relationships. Lead poisoning is a slow acting, debilitating disease. Lead-poisoned birds are more susceptible to natural predators, and are often mistaken for cripples. Therefore, a victim of lead poisoning may not immediately be identified. In the 1980's the National Wildlife Health Center conducted a widespread study of more than 8,000 waterfowl in geographically distant sites throughout the U.S. that confirmed a lead poisoning level of between 2 and 3 percent nationwide. In addition, of more than 2,000 bald eagles examined by Fish and Wildlife Service laboratories from 1963 to 1986, 119 had been diagnosed as having died of lead poisoning.

For more information on this lead shot ban or the study of lead poisoning, contact Chris Franson, (608) 270-2400


1989

Exxon-Valdez Oil Spill

Exxon-Valdez Oil Spill Decimates Wildlife

When the Exxon-Valdez ran aground on the Bligh Reef in 1989, wildlife in the area experienced extreme die-offs. Some estimates indicate that over a quarter million sea birds were killed, as well as 300 harbor seals and 250 bald eagles. 38 thousand of these deaths were reported to the National Wildlife Health Center from October to December 1989.

Scientists at the National Wildlife Health Center were able to determine the cause of death for the overwhelming majority of these animals was related to the spill. The wildlife necropsies, combined with the Center's excellent record in court trials, helped lead to the $150 million settlement between Exxon and the U.S. government.

For more information contact Milt Friend, (608) 270-2400


1983-1985

Lead poisoning study

Lead poisoning study

From 1983 through 1985, the National Wildlife Health Center conducted exhaustive studies in geographically disparate sites that would eventually lead to a ban on toxic lead shot for hunting.

The Fish and Wildlife Service made efforts to understand the connection between lead poisoning and the use of lead shot for hunting as early as the 1930's. But there were difficulties in trying to understand these relationships. Lead poisoning is a slow acting, debilitating disease. Lead-poisoned birds are more susceptible to natural predators, and are often mistaken for cripples. Therefore, a victim of lead poisoning may not immediately be identified. In the 1980's the National Wildlife Health Center conducted a widespread study of more than 8,000 waterfowl in geographically distant sites throughout the U.S. that confirmed a lead poisoning level of between 2 and 3 percent nationwide. In addition, of more than 2,000 bald eagles examined by Fish and Wildlife Service laboratories from 1963 to 1986, 119 had been diagnosed as having died of lead poisoning.

For more information on the lead shot ban or this study on lead poisoning, contact Chris Franson, (608) 270-2400


1982

Lichens studied for mercury

Plants and Lichens as Indicators of Atmospheric Deposition

The natural world is continuously exposed to atmospheric contaminants from sources such as industry, cities, and power plants. The magnitude of emissions from these sources, combined with the atmosphere?s ability to carry those emissions great distances allow remote, supposedly pristine areas such as Isle Royale National Park in Lake Superior to be exposed. Elements such as mercury and lead, which are toxic to many organisms as they are passed up the food chain, are found in National Parks throughout the U.S.

In the terrestrial world, air pollutants are deposited on plant foliage and the soil surface, so rooted plants may take up elements through leaves directly, or through roots in the soil. Mobility of elements within plants is determined by examining the plant?s physiology; analysis of plant parts elucidates the pathways of deposition. Arsenic, for example, is highly toxic, and is usually confined to roots. Analysis of soils determines element concentrations already present. These studies also help determine if there are naturally high levels of certain elements present from geologic anomalies. For example, high levels of mercury are found in some plants in Yellowstone National Park due to emissions from geothermal features.

Lichens are small symbiotic plants that grow on trees, rocks, and soils. They have no roots and are totally dependent on the atmosphere for their nutrition. They receive no sustenance from their hosts, just physical support. Thus elevated concentrations of certain elements in lichens are a sure sign of atmospheric deposition. Studies of the presence and absence of sensitive lichen species, and element concentrations in their tissues are ways of discovering atmospheric impacts in the area. Some studies are performed along transects downwind of point sources (tall stacks, for example) to determine the amount and geographic distribution of fallout from the source. Lichens are transplanted from pristine to polluted areas to determine the continued presence of atmospheric pollutants. Common species, such as Hypogymnia physodes, are used for sampling element deposition because of their widespread distributions. Nutritional elements are commonly studied, in addition to elements known to be emitted anthropogenically, such as lead, mercury, cadmium, and chromium.

Since 1982, these types of studies have been performed in 42 National Parks and refuges. About 3,000 lichen samples representing 50 or more species have been collected from around 400 localities. Researchers tested these samples for 22 chemical elements, providing an estimated 50,000 data points for analysis. These data are archived for use by other researchers and for comparisons over time. This research helps to document the effects of air pollution on park and refuge vegetation and assists managers by alerting them to potential air pollution problems.

For more information, check out our fact sheet or contact Jim Bennett, 608-270-2442


Early 80's

Avian cholera outbreaks

Avian cholera outbreaks

Avian cholera is caused by the bacterium Pasteurella multocida, which can kill in as little as six hours. The disease is fatal to roughly half of the infected birds. Healthy birds can be infected by live bacteria released by dead or dying birds, as well as seemingly healthy birds that have been carrying the disease. Dense concentrations of waterfowl enhance transmission opportunities, so avian cholera can sometimes spread through a wetland quickly, killing thousands of birds in a single outbreak.

National Wildlife Health Center scientists, in collaboration with state, national, international, and non-governmental agencies, conducted research for three years to determine, finally, that the prevalence of cholera in the wild is probably due to disease carriers, birds that previously contracted the disease and survived. Scientists also determined that exposure to the cholera bacteria, Pasteurella multocida, can occur in bird populations in seemingly disease-free areas. These results are significant because experts previously believed almost all infected birds died due to the swift and lethal nature of avian cholera.

To learn about the critical role USGS National Wildlife Health Center scientists played in understanding this disease, download our Avian Cholera information sheet (1,298 kb). Click here to find out the facts about Avian Cholera. And for further information, contact Mike Samuel, (608) 270-2400.


1977

Bear River Station: A New Beginning

A New Beginning for Wildlife Health Science

Wildlife disease has been around as long as there has been wildlife, but until the early 1900s, wildlife disease was largely ignored, especially at the national level. After all, "You can't do anything about wildlife diseases," a university professor is rumored to have argued to a microbiologist, "so why do you need to know anything about them?"

"Well," the microbiologist argued, "if you don't know anything about them, of course, it's a cinch you can't do anything about them-anything intelligent, at any rate."

That microbiologist was Dr. Wayne Jensen, the lead researcher at the U.S. Fish and Wildlife Service Bear River Field Station in Utah, whose research on avian botulism spanned decades and remains immeasurably valuable in understanding the impact of that disease. Before Jensen's work at Bear River, prior to World War II, efforts in wildlife disease work were sporadic. Some regional efforts, like the work of the California Department of Fish and Game as well as the Southeast Cooperative Wildlife Disease Study, produced excellent results, and the first complete study on avian botulism was published in the early 1930s by the U.S. Department of Agriculture. However, there was no comprehensive agency involved in wildlife disease throughout the nation, and the Bear River station was, until the mid 1970s, one of no more than a dozen federal locations where wildlife disease was the subject of serious scientific inquiry.

For more information on the Bear River Field Station, call Milt Friend, (608) 270-2400.


1975

National Wildlife Health Laboratory

The National Fish and Wildlife Health Laboratory Officially Opens its Doors

In 1975 the National Fish and Wildlife Health Laboratory didn't actually have a laboratory of its own, we shared with the University of Wisconsin-Madison. We shared a lot of things with the University, including our first 1975 office in the University's Stock Pavilion, which came complete with an articulated cow skeleton. Despite the occasional horse walking through the halls, the beginnings of the National Wildlife Health Center was functional, and we have been serving the Nation ever since.

For more information on the early history of the National Wildlife Health Center , contact Milt Friend, (608) 270-2400.

Wildlife field support

Investigating Wildlife Diseases in the U.S.

Disease is an important limiting factor of some wild animal populations. Monitoring disease through detailed investigation can lead to better understanding of the ecology of disease and provide insight for developing preventative management strategies. Wild animals are often early indicators of problems within the environment. Therefore, it is crucial to investigate diseases as they can affect the natural resources that are under the stewardship of the Department of the Interior.

Investigating the causes of illness and death in wildlife has been a primary objective of the USGS National Wildlife Health Center (NWHC) since the mid-1970s. To successfully investigate disease events, the NWHC applies a multi-disciplinary approach. Highly trained specialists in pathology, microbiology, parasitology, toxicology, and wildlife biology combine their skills to put the pieces of the disease puzzle together. Results from investigations are used to assess the risk to the wildlife populations involved. Compiling information from several investigations can be useful for developing mathematical models that combine environmental and anthropogenic factors that may influence future disease events. After an assessment of these data, technical knowledge is provided to field biologists and wildlife managers so that they can better control or prevent diseases. Communication is a key component of this approach. The wildlife disease specialists at NWHC have established a network of near-continuous communication with field biologists throughout the Nation.

Wildlife are frequently remote and not readily accessible. To obtain the best specimens that are critical to successful investigations, NWHC specialists have trained field biologists to recognize abnormal situations and to properly collect samples to send for testing. Well-trained biologists become the ?eyes and ears? in the field. Reporting results and conclusions back to the field biologists completes the communication circle fundamental to successful disease investigation. Many times, disease investigations lead to the discovery of new diseases.

During the fiscal year 2003, the National Wildlife Health Center received 2,559 diagnostic cases (cases consisting of a single animal to several animals), and 202 epizootic events were reported (many animals from the same location during a short time span). Agencies most often sending cases to the NWHC were the U.S. Fish and Wildlife Service and state wildlife management agencies. Highlights of investigations in 2004 include the discovery of a new infectious agent that has nearly decimated the endangered Mississippi Gopher Frog. Without protective steps to avoid cross-pond contamination, this pathogen (disease-causing agent) could become a major disease of amphibians. Another important pathogen was described in frogs but is already known as a pathogen of oysters. This finding suggests that the source of the pathogen in oysters may be upstream of the estuaries where oysters live. West Nile virus (WNV) was detected in several new species of wild birds. In particular, the American White Pelican in the Dakotas and the endangered Red-Cockaded Woodpecker in the southeast have recently sustained large mortality events that may have resulted from WNV. A new diagnostic test was developed for the detection of WNV in bird carcasses. Researchers determined that the pulp of newly emerging feathers in infected birds contains a large amount of virus, and that this sample type is superior to tissue pools (spleen and kidney) and oral swabs (oral or cloacal) for the detection of virus. New feathers (blood feathers) can be easily pulled from carcasses and shipped for testing.


1973

Lake Andes Duck Plague

Lake Andes Duck Plague

In January 1973, more than 40 percent of the 100,000 mallards died while wintering at the Lake Andes National Wildlife Refuge in South Dakota . This devastating die-off, the largest ever recorded due to duck plague, was the single most significant event driving the creation of the National Wildlife Health Center.

Some scientists speculate the waterfowl surviving the Lake Andes die-offs became disease carriers, and subsequently infected other waterfowl populations, contributing to the recent emerging characteristics of this disease. However, because duck plague is difficult to detect in birds that have survived exposure to it, this conclusion remains speculatory.

For more information about this historic die-off event, contact Gail Moede Rogall, (608) 270-2438.


 

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