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.

Top: A black-legged tick, also known as a deer tick, is the most common carrier for Lyme disease. Bottom: A microscopic image of the bacteria Borrelia burgdorferi, which causes Lyme disease

Lyme Disease: Once Bitten Twice Shy

Most everyone has found an unwelcome tick hitchhiking on a pants leg after a ramble through some brush or have felt one walking up the back of their neck after spending time in a wooded area. As a child you may have remembered your mother snatching a tick off your arm as its tiny legs held tight.

Ticks can be a nuisance and their bites can cause irritation.  More importantly, ticks have the distinction of spreading the widest variety of disease producing agents that are harmful to humans.

Lyme disease is the most commonly reported tick-borne disease in the Northern Hemisphere and if left untreated infection can spread to the joints, the heart and even the nervous system.

 Lyme Disease History

The disease was initially named after the town of Lyme, Conn.where a number of cases were first reported in 1975.  The emergence of the disease infected ticks has been linked to changing land use patterns as forested areas were cleared for agriculture and the white-tailed deer population dwindled in the late 1800s in the north eastern United States.  The black-legged tick, or “deer tick,” the principle vector, or carrier of Lyme disease, made a comeback with the return of forested habitat in mid-1900s and the risk of human infection increased.

Since the mid-1970s Lyme disease has spread throughout New England, the Mid-Atlantic and the northernMidwest with cases reported in nearly every state.

USGS Science and Lyme Disease

Although the black-legged tick can be found throughout the Eastern United States, scientists were baffled as to why the Lyme disease cases were not found in all the places where the ticks carrying it were found.  The USGS has collaborated with several universities in a National Science Foundation funded study to better comprehend the ecological drivers for the geographic disparity in Lyme disease risk in the Eastern United States.

Data on tick-host relationships, seasonal tick biology, and tick genetics will be studied after they are collected in nine separate field sites around the United States.  Dr. Howard Ginsberg, a USGS Research Ecologist with the Patuxent Wildlife Research Center, is a Principle Investigator with the project.  He explains that the application of modeling tools will help to shed light on the ecological processes liable for the variation in Lyme disease cases and may help to predict how climate change could affect this risk.   “Lyme disease is a major public health problem,” said Dr. Ginsberg “and the reasons for its geographical distribution are ecological. The knowledge to be gained from this project will help us better predict the future distribution of this disease, and lower the risk to human health.”

The goal of the study is to better understand how the relationships between ticks, their hosts, and environmental factors influence disease transmission, which can lead to improved tick control measures and public awareness on the regional variation in the risk of Lyme disease.

What are the Signs and Symptoms of Lyme Disease?

Lyme disease is the most commonly reported tick-borne disease in the Northern Hemisphere and if left untreated infection can spread to the joints, the heart and even the nervous system. Photo credit: Creative Commons.

According to the Centers for Disease Control and Prevention (CDC)  symptoms of Lyme disease may present themselves within a few weeks of being bitten by an infected tick.  Symptoms that require immediate health care evaluation include:

• Chills or fever
• Aches and pains including headache and muscle and joint pain
• A bull’s-eye rash which begins at the site of the tick bite and may appear within 3-30 days and is usually circular and called erythema migrans  or EM.

What Can Be Done to Help Prevent Lyme Disease?

Because ticks are most active in the warmer months, the CDC advices the following measures in tick season (April-September):

• Avoid wooded and brushy areas with high grass.
• When hiking walk in the center of the trail.
• Use insect repellents such as DEET and use Permethrin products on outdoor clothing.
• Shower or bathe as soon as possible after coming indoors and check clothing, gear, and pets for ticks.
• Conduct a full body check for ticks and examine children carefully, especially behind the knees, on the scalp, under the arms, and around the ears and waist.
• Remove ticks promptly and carefully

Lyme disease patients treated early with antibiotics normally recover quickly and completely.  A small percentage of patients have lingering symptoms and may need to receive a prolonged course of antibiotics.

Your best defense is to avoid tick infested areas and be vigilant in looking for unwelcome hitchhikers.

Back-lit photographs of wings of White-nose Syndrome (WNS)-positive little brown bats, one with subtle circular and irregular pale areas (arrows) indicating areas of fungal infection (A) and another bat (B) with areas of relatively normal tone and elasticity (black arrow), compared to a WNS affected area that looks like crumpled tissue paper with loss of elasticity, surface sheen and areas of irregular pigmentation (white arrow). (C) Microscopic section of wing membrane from a little brown bat showing extensive infection with the fungus (magenta structures), G. destructans.

The United States is under an economic and ecological siege by alien invaders — America’s Most Unwanted. More than 6,500 of these harmful non-native species cause more than 100 billion dollars in damage each year to the U.S. economy as the country battles to control the economic, ecological, and health threats these invaders pose. Increased global travel and trade are providing more pathways for both intentional and unintentional introductions of invasive species.

Invasive species affect just about everyone in every State in the country, in urban centers and wilderness areas. And their costs are borne by all of us — farmers, ranchers, businesses, and local, State, Tribal, and Federal governments.

The Cost of Invasives

Costly effects of invasives include crop decimation (cactus and gypsy moths), clogging of water facilities (quagga and zebra mussels) and waterways (hydrilla, giant salvinia), wildlife and human disease transmission (West Nile virus, monkeypox, and diseases in some ships’ ballast water), threats to commercial, native, and farmed fisheries (Asian carp, snakehead fish, sea lamprey, Asian swamp eel, whirling disease, and viral hemorrhagic septicemia), increased fire vulnerability (cheatgrass, brome, and buffelgrass) and adverse effects for ranchers and farmers (leafy spurge and cheatgrass).

Researchers with the USGS Invasive Species Program work on every one of those species mentioned; in fact, our researchers work collaboratively on all significant groups of invasive organisms in terrestrial and aquatic ecosystems in all regions of the United States. Across the Nation, our invasive species experts partner with States, other Federal agencies, businesses, agriculture, and natural resource managers to help solve the problems posed by these invaders.

Key components of invasive species activities include prevention, monitoring and forecasting threats, and control and management of established invaders.

During Invasive Species Awareness Week, we will feature some of America’s Most Unwanted each day to highlight the impacts of invasive species to the nation’s Ecosystems and economy.

The USGS National Wildlife Health Center conducts a bat autopsy as part of its efforts to study the fungus that causes white-nose syndrome in bats.

Invasive Wildlife Diseases: USGS scientists collaborate with public health and animal health agencies on notable invasive zoonotic diseases – invasive diseases that are transmissible between animals and people. Such diseases are a potential collateral result of exotic animal introductions. Specialized biological containment facilities at the USGS National Wildlife Health Center (NWHC) in Madison, Wisconsin, allow scientists to provide diagnostic surveillance and research, information needed by all levels of government to adequately respond to wildlife diseases. NWHC scientists used patterns of wild bird mortality from West Nile virus, a wildlife disease introduced to the United States in 1999, as an indicator of the spread and activity level of this emerging disease. This information allowed public health officials to estimate human population risk and enact control and prevention activities. USGS and USDA surveillance also indicated that monkeypox, an invasive disease introduced to the United States from Africa through the international pet trade, had not spread from pets or humans to free-living wildlife. Since 2006, USGS along with other agencies, has been conducting surveillance and monitoring of wild birds to detect highly pathogenic avian influenza, an important zoonotic and economic disease, if it invades the United States through migratory birds.

An Emerging Bat Disease: The sudden emergence of white-nose syndrome (WNS), a devastating disease of hibernating bats, demonstrates the importance of a national and international infrastructure to investigate and respond to emerging wildlife diseases and their ecological and societal threats. Since 2008, when scientists first began investigating this unknown disease in bats of the northeastern U.S., WNS has spread to 16 states and 4 Canadian provinces. WNS has caused precipitous declines of some bat species.  Not only are bats important ecologically, but a recent USGS and partner study showed their pest control services likely save the U.S. agricultural industry at least $3 billion a year.  Since the USGS first identified the WNS fungus, our ongoing research has provided critical information about the fungus and the disease, guiding state, federal, NGO and tribal disease-response activities. Land-management agencies rely on our research and disease investigations to support on-the-ground actions, to help develop the WNS National Plan, and to assist with other national disease-management plans.

Little brown bat with fungus on muzzle.

Viral Hemorrhagic Septicemia Virus:

Viral hemorrhagic septicemia virus (VHSV) is among the most important viral pathogens of finfish, causing losses in both freshwater and marine species. In 2005-2006, VHSV emerged in the Great Lakes Basin, resulting in a series of fish kills. As of June 2011, the virus has been found in 31 fish species from Lakes Erie, Superior, Huron, Michigan, Ontario, St. Clair, as well as the Niagara and St. Lawrence rivers, and inland lakes in Michigan, New York, Ohio, and Wisconsin. Significant VHSV outbreaks have affected many species of fish, such as muskellunge, freshwater drum, goby, burbot, yellow perch, gizzard shad, and smallmouth bass. Research by USGS scientists, in collaboration with state, federal, and Canadian partners, focuses on using molecular genetic tools to identify and track strains of the virus, developing improved diagnostic methods, determining methods for disinfection of eggs, and testing for virus transmission pathways. A three-year project funded by the Great Lakes Fishery Trust to the USGS’s Western Fisheries Research Center and colleagues at Cornell University and Michigan State University has allowed USGS scientists to compare the genetic sequences of VHSV strains obtained from fish at 37 locations in the Great Lakes Basin with those representing strains from other regions of the world. The very low level of genetic diversity within the Great Lakes is consistent with a recent, single introduction of VHSV to a native population of fish. To date, the route of introduction has not been determined.

Viral hemorrhagic septicemia has recently emerged in the Great Lakes and caused severe epidemics in many fish species.

For more information on USGS research on invasive diseases:

USGS Viral Hemorrhagic Septicemia Virus Page

National Wildlife Health Center

National Wildlife Health Center Avian Influenza Research

National Wildlife Health Center White-nose syndrome research

USGS Monkeypox fact sheet

Vaccination and Flea Control to Assess Invasion of Plague into the Conata Basin, South Dakota

Development of a White-nose Syndrome Disease Tracking System

Fort Collins Science Center: White-nose syndrome

Evaluation of the Efficacy of Iodophor Disinfection of Walleye and Northern Pike Eggs to Eliminate Viral Hemorrhagic Septicemia Virus