Culex species mosquito biting a human hand.

A deadly disease spread by the bite of infected mosquitoes continues to afflict people and wildlife in the United States.

Human deaths from West Nile virus (WNV) are alarmingly high for 2012, as this year is on track to become the worst West Nile virus epidemic ever in the United States. The Centers for Disease Control and Prevention  reports that more than 120 people this year have died from a fatal inflammation of the brain (encephalitis) caused by WNV, and the disease has been diagnosed in more than 2,630 people.

Wildlife also suffer from the disease, which is transmitted by infected mosquitoes (primarily members of the Culex species) to more than 100 species of birds and to nine mammal species including humans and horses. Evidence of infection has also been reported in amphibians and in reptiles such as alligators.

The virus was first discovered in the West Nile area of the east African nation of Uganda in 1937. From 1950 onward, it spread throughout the Mediterranean and Europe. In 1999 the first North American case was diagnosed in wildlife in Queens, N.Y., and that’s when the USGS became involved.

USGS Science and West Nile Virus

For nearly 40 years, the USGS National Wildlife Health Center  (NWHC) has been working to advance wildlife and ecosystem health by identifying, understanding and responding to disease threats to our native wildlife, as well as sharing that information with public health and domestic animal health agencies.

Screenshot of the USGS West Nile Virus website

In the case of West Nile virus, on Sept. 2, 1999, the NWHC was contacted by New York state officials regarding sick, dying and dead American crows. After the disease was identified as West Nile virus, the USGS also provided diagnostic and technical assistance to state health departments to test dead birds as part of an emerging WNV surveillance effort. This assistance eventually expanded to include 25 states until local public health departments began to develop their own surveillance and testing capabilities. The CDC provided funding for this effort.

The USGS Eastern Geographic Science Center began collaborating with the CDC in 2000 to use the surveillance data to produce weekly national maps depicting surveillance efforts by counties within U.S. states and the presence of WNV. As a result of the development of these disease maps, USGS now produces GIS mapping and graphic products that show the occurrence and distribution of West Nile virus and other wildlife diseases by county, state and by week of occurrence.

West Nile Research at USGS Now

Emerging pathogens such as WNV pose a major threat to conservation efforts in maintaining the health of wildlife, in particular birds. Wild birds are the principal hosts of WNV, and many birds die from WNV infections. Greater sage-grouse, American white pelicans, and species groups such as corvids (crows, jays, ravens, and related species), and raptors are quite susceptible to WNV and continue to be the focus of research on WNV at NWHC.

USGS scientists are involved in laboratory studies of WNV, and research on free-living wild birds is on-going at many USGS science centers. Resource managers and scientists are especially concerned about the effect of this virus on greater sage-grouse and American white pelicans. Both species were imperiled prior to the arrival of WNV; because they are highly susceptible to this disease they have experienced widespread mortality.

Thus far WNV has never been reported in Hawaii. However, resource managers and others are greatly concerned that if WNV becomes established in that state, it could devastate the native Hawaiian bird community. Hawaiian forest birds, some species of which are among the most endangered birds in the world, would be at risk from the disease in the event WNV spreads to the islands. The USGS is working with the U.S. Fish and Wildlife Service in Hawaii as well as the U.S. Department of Agriculture to conduct WNV surveillance.

Sage-grouse have declined throughout their entire range, largely due to the loss and fragmentation of sagebrush habitat.

One Health: The Connection between Global Health and Domestic Animal, Wildlife, and Human Disease

The USGS is vigilant for newly emerging and re-emerging wildlife diseases, as well as monitoring existing wildlife health concerns. Virulent Newcastle disease in cormorants, avian influenza in waterfowl, and white-nose syndrome in bats are just a few of the diseases USGS tracks. The Eastern Geographic Science Center is mapping the occurrence of arboviral diseases that have a wildlife- mosquito cycle: West Nile virus, St. Louis encephalitis, eastern equine encephalitis, western equine encephalitis, and La Crosse encephalitis. In addition to the maps displayed on USGS web pages, at the county level these pages also provide epidemiological information including a histogram of disease cases per week over time, tables of disease cases by state, and other related information. The USGS has been producing West Nile virus surveillance maps since 2000 and plans to continue this highly valued partnership with CDC into the future.

Studying diseases in wildlife is obviously important work for the health and welfare of wildlife, but it is also important for the health of humans and domestic animals—70 percent of recent emerging human diseases originated in wildlife or domestic animals, including West Nile virus, plague, AIDS, SARS and avian influenza. The health of humans, animals — wild and domestic — and ecosystems are all inter-related; this is the concept of “One Health,” which advocates understanding and appreciating the links among human, animal and ecosystem health, and the importance of and commitment to working together to address health challenges.

Harbor seal pup.Harbor seal pup. Source: http://www.public-domain-image.com/fauna-animals-public-domain-images-pictures/seals-and-sea-lions-public-domain-images-pictures/harbor-seal-pictures/harbor-seal-mammal-phoca-vitulina.jpg.html

When more than 162 young harbor seals were discovered stranded or dead on New England beaches in the fall of 2011, it was officially declared by the federal government as an Unusual Mortality Event (UME). For marine mammals, a UME is a stranding that is unexpected, involves a significant die-off of the population, and demands an immediate response.

Start with Science

The National Oceanic and Atmospheric Administration (NOAA) assembled a team of scientists to investigate. Wildlife experts from the USGS National Wildlife Health Center contributed their expertise by isolating the virus from the tissues of the seals. They were able to characterize the virus as a type of influenza virus most closely related to the avian influenza H3N8 viruses commonly found in wild birds.

Collectively, the team of scientists determined that the H3N8 seal virus is likely to have caused the 2011 mortality event in New England.  Further, it may pose a continued threat to marine mammals on the nation’s coast.  Dr. Hon Ip, a USGS virologist at the National Wildlife Health Center, said, “What was surprising was that the seal virus contained genetic changes that have been shown to increase mammalian infection. Of the influenza viruses that have been previously isolated from seals, none shows this pattern of genetic change toward adapting to mammals.”

Katie Pugliares and Michael O’Neil with the New England Aquarium preparing a harbor seal carcass for necropsy. Photo Credit: New England Aquarium.

Is there a Wildlife-Human Connection?

In the last few years, the highly pathogenic avian influenza H5N1 virus has been shown to cause disease and even death in cats, dogs and people. It is estimated that more than 70 percent of the emerging infectious diseases that can infect people have a wildlife origin. The seal H3N8 virus, and its adaptation to mammals, raises questions about whether this virus may be the latest example of an emerging infectious disease

Future Efforts for a Healthy Marine Ecosystem

While the importance of potential threats to human health and domestic animals from pathogens is of concern, these emerging pathogens are also a potential threat to conservation efforts in regard to maintaining the health of wildlife such as harbor seals and the overall function of a healthy marine ecosystem.

The National Wildlife Health Center is at the forefront of identifying and understanding disease threats to our native wildlife, as well as sharing that information with public health and domestic animal health agencies.  Partnerships, such as this effort with the NOAA investigative team, foster better understanding of the epidemiology and ecology of wildlife disease, provide better information for management decisions, and ultimately help protect the health of all species.

The investigative team from the USGS, Columbia University, NOAA, New England Aquarium, Sea World, and the EcoHealth Alliance recently published its findings on the influenza virus that fatally afflicted the harbor seals in the scientific journal mBio.

Dead harbor seal found in New England in 2011. Photo Credit: New England Aquarium.

More Information

Visit the USGS National Wildlife Health Center homepage.

Learn more about USGS avian influenza research.

Find out what other research the USGS is doing on microbiology.

A comparison of normal coral with some dead skeletal material covered by typical secondary colonization (right) and a wilting, dying coral covered with oil plume debris (left). Also affected were brittlestars, seen climbing in the healthy coral. Image courtesy of, Lophelia II 2010, NOAA OER and BOEM

Nearly two years after the Deepwater Horizon oil spill, the meticulous, long-term efforts of scientists finally yielded the official results: namely, that the brown, wilted, dying corals found at the Mississippi Canyon lease block 294 were indeed damaged by a plume of oil from the spill.

For many, it seemed a foregone conclusion. Back in December 2010, when news of the damaged corals first came out, their proximity to the leaking Macondo well seemed to be a “smoking gun” in its own right. What else could brown gunk (flocculent matter, if you are a scientist) covering damaged corals seven miles from the Deepwater Horizon site be, if not oil from the spill?

Yet, to this team of scientists, it was worth taking a closer look at the evidence with two-dimensional gas chromatography, sediment cores, coral samples, and mosaic imagery. Why? Because so much was at stake.

In order to understand the damage in the deep, the scientists had to start by understanding what was down there to begin with.

Amanda Demopoulos sorts and identifies the animals in a sieved sample. Image courtesy of, Lophelia II 2009: Deepwater Coral Expedition: Reefs, Rigs and Wrecks.

To support that mission, enter USGS research benthic ecologist Dr. Amanda Demopoulos, who studies life on the sea floor to piece together what types of organisms typically live together in deep sea communities. Her work involves digging sediment cores from the bottom of the ocean and sorting through the many tiny forms of life found there.

In addition to deep sea coral ecosystems, Demopoulos studies communities in parts of the Gulf where oil naturally seeps up from the seafloor and is in fact a wellspring of life, not a source of damage. Chemosynthetic ecosystems – the ones where food webs are based on chemicals rather than sunlight – tend to have different forms of life, such as tubeworms.

Demopoulos was on the November 2010 research expedition which first discovered the damaged corals. Funded by the National Oceanographic and Atmospheric Administration and the agency now known as the Bureau of Ocean and Energy Management, the goal of that expedition was to gather the basic data needed to construct a scientific understanding of the various undersea ecosystems.  It was part of a decades-long collaborative effort among federal and university scientists to explore deep sea ecosystems in an effort to provide sound baseline information for governance decisions about how to best balance natural resource use with protection. Demopoulos recalled watching the first images from the damaged site come in from remotely-operated vehicle.

An impacted coral with brittlestar climbing through it. Image courtesy of, Lophelia II 2010, NOAA OER and BOEM

“When we were watching the ROV video in the lab, I looked up at the video screen, and it looked starkly different from anything we’d ever seen before,” Demopoulos said. “The corals were all dark grey and lumped over, and it was clear these animals were not healthy. We’d seen dead coral, but this was so different, we immediately knew it was worth investigating further. When we got closer, there didn’t seem to be any secondary colonization, as we’d seen in the past on dead coral.”

The fact that no new animals — such as barnacles or hydroids — had begun to attach to and grow on the dead corals suggested the coral deaths had been recent, noted Demopoulos. This process, known as secondary colonization, is commonly observed on dead corals, but takes time to occur.

After the discovery of the damaged coral, Dr. Charles Fisher from the Pennsylvania State University led a follow-up expedition to more carefully investigate the damage itself, supported by a special National Science Foundation RAPID grant. Fisher worked with Dr. Helen White from Haverford College, Woods Hole Oceanographic Institute, Temple University, USGS and BOEM to assess the damage.

This push core shows discrete layers in a typical sediment sample. The light brown organic layer sits above a dark gray clay sediment. Most of the animals are found in the top layer of sediment. Image courtesy of, Lophelia II 2009: Deepwater Coral Expedition: Reefs, Rigs and Wrecks.

Demopoulos’ part in the overall effort to understand life in the deep ocean has been to understand what lives in the sediments of different types of environments, such as deep-sea corals and chemosynthetic communities. Some species may be generalists found in a variety of environments, while others will be unique to one type of habitat. Demopoulos also pieces together new information about how these tiny organisms are connected through food webs.

Without a baseline for understanding what is typical, Demopoulos would not be able to assess how those sediment dwellers were affected by the oil spill. Based on her expertise with sediment samples, Demopoulos helped design the best approach for assessing the corals at the Mississippi Canyon lease block 294 for the presence of oil and the extent of damage.

“The challenge we faced in this study was piecing together what happened from multiple lines of evidence, because no one was sitting on the sea floor when the plume went by. The corals were the only witness,” said Demopoulos, “We had to consider the proximity to the Deepwater Horizon site and the fact a deep-water plume had recently passed over the site, then closely examine the corals for tissue damage and signs of stress, such as the presence of mucus, and of course, the chemical signature of the oil. It was truly an interdisciplinary effort.”

Demopoulos pointed out that the cumulative knowledge about deep-sea communities from previous expeditions provided the baseline for scientifically assessing what they saw at the site.  “This is but one site in the Gulf of Mexico,” she said, “but it has shown how important it was for us to have a frame of reference as to what a healthy deep-sea coral ecosystem looks like. We are still trying to understand the extent to which this is occurring elsewhere in the Gulf of Mexico.”

The results of the efforts were recently published in the Proceedings of the National Academy of Sciences of the United States.

Little brown bat with fungus on muzzle.

Winter Home

Missouri has more than 6,300 caves and the implications for the potential spread of WNS farther west are profound. Missouri caves provide winter habitat for more endangered Indiana bats than any other state outside of Indiana.  Three Missouri caves used by endangered gray bats provide critical winter habitat for approximately one quarter of the known hibernating population of that species. Detection of WNS in Missouri also indicates the disease may continue spreading towards the range of more than a dozen additional species of hibernating bats that occur only west of the Great Plains.

What Is It?

White-nose sydrome results from a skin infection of hibernating bats by a fungus previously unknown to science, Geomyces destructans; and is named for the white fungus often seen on the muzzles, ears, and wings of bats. This disease poses a threat to cave hibernating bats of the United States, Canada, and potentially all temperate regions of the world. In 2011, scientists from the USGS National Wildlife Health Center published a study confirming the cold-loving fungus G. destructans is the cause of WNS.

Where Is It?

Hibernating little brown bat with white muzzle typical of White-nose syndrome.

This devastating disease affecting hibernating bats has spread from the Northeast to the mid-Atlantic to the central United States. Since the winter of 2007-2008, millions of insect-eating bats have died from this emerging disease in the eastern US and Canadian provinces.

Within the last two years, WNS has been confirmed in several central states, including Alabama, Indiana, Kentucky, and Tennessee. However, high mortality of bats has not yet been reported at these locations. The US Fish and Wildlife Service estimates bat mortality in the northeastern US since the emergence of WNS has exceeded 5-6 million bats, however, it remains to be seen if WNS will develop and manifest with similar severity in other parts of the country.

Hard at Work

Scientists at many Federal and State agencies and academic institutions are pursuing research to better understand this disease in an effort to manage its spread. The USGS National Wildlife Health Center, the USGS Fort Collins Science Center, along with the U.S. Fish and Wildlife Service, the National Park Service, and other partners continue to play a primary role in WNS research.

Studies conducted at the NWHC led to the discovery, characterization, and naming of the causative agent of White-nose syndrome, G. destructans, and to the development of standardized diagnostic criteria for diagnosing the disease. Additionally, NWHC has pioneered animal husbandry and laboratory techniques for studying impacts of the fungus to hibernating bats.

Long-Term Impacts

Most of the species affected by WNS are long-lived and have only a single pup per year. Subsequently, bat populations do not fluctuate widely in numbers over time, and it is unlikely that species of bats affected by WNS will recover quickly. The sudden and widespread mortality associated with WNS is unprecedented in hibernating bats, among which widespread disease outbreaks have not been previously documented. In temperate regions, bats are primary consumers of insects, and a recent economic analysis indicated that insect suppression services (ecosystem services) provided by bats to U.S. agriculture is valued between 4 to 50 billion dollars per year. However, the true ecological consequences of large-scale population reductions currently under way among hibernating bats are not yet known.

Insect-eating bats provide a great pest-control service to agriculture and natural ecosystems.