Home Archived April 13, 2016

U.S. Geological Survey

Maps, Imagery, and Publications Hazards Newsroom Education Jobs Partnerships Library About USGS Social Media

USGS Newsroom

USGS Newsroom  

USGS Reports That West Nile Virus Goes Beyond Crows
Released: 11/17/1999

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Paul Slota 1-click interview
Phone: 608-270-2420

Robert McLean
Phone: 608-270-2401

NOTE TO EDITORS: Dr. Robert G. McLean, Director of the USGS National Wildlife Health Center, Madison, Wis., will testify at a congressional field hearing on the West Nile virus, slated for December 14, at Fairfield University, Fairfield, Conn. The hearing will be in the School of Business Dining Hall. Dr. McLean will be available following the hearing. For more information on the hearing, call Olivia Ferriter, 703-648-4054.

The virus that can cause West Nile encephalitis in humans is not only found in crows, according to scientists at the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wis. USGS has recently released a list of 18 bird species that the Centers for Disease Control and Prevention(CDC) in Fort Collins, Colo. confirmed as having tested positive for the West Nile virus, including:

American crow
Ring-billed gull
Yellow-billed cuckoo
Rock dove
Sandhill crane
Blue jay
Bald eagle
Laughing gull
Black-crowned night-heron
American robin
Fish crow
Red-tailed hawk
Broad-winged hawk
Cooper’s hawk
Belted kingfisher
American kestrel
Herring gull

"Although the cause of death has not been determined in all cases, we can assume that these birds were exposed to the virus in the tri-state area of New York, New Jersey and Connecticut," said Dr. Robert McLean, USGS wildlife biologist and director of the Madison Center. "Some of these species could play a significant role as we track the spread of this disease."

McLean added, "The variety of birds is disturbing because many of these species migrate to other areas and could potentially disseminate the disease elsewhere. The good news is, with the exception of American crows, there were only a few individual birds from each respective species thattested positive. It is still too early to tell if this is because they are not as susceptible or they were not as readily observed as crows."

Monitoring mortality in American crows is especially important because crows appear to be highly sensitive to the virus. Since many crows normally travel less than 200 miles they can act as sentinels for local transmission of the disease.

"At this time it is difficult to assess how many birds have died from this disease. While some of the affected areas have reported very high bird mortality, especially in crows, a number of the birds have died from other causes," said USGS wildlife disease specialist Linda Glaser. "About 49percent of the 392 birds tested by the USGS and CDC have tested positive for West Nile virus."

McLean and his team of USGS biologists have been taking blood samples from migratory and non-migratory birds in the New York area to get a sense of the extent that bird populations and various species were exposed to thevirus. "This information, in addition to being shared with the CDC, will be used in establishing an effective surveillance network to track the virus and ultimately learn how it could impact our native bird populations," saidMcLean.

There is still much that is unknown about the ecology of the virus and how it will respond to its new environment in the United States. "Once a bird is infected, the virus can be transmitted to mosquitoes only for about 4 to 5 days. Although this appears to be a short time, many birds can migrate hundreds of miles within that time. It will be important to find out what species are involved in the transmission of the virus and if migratory birds, including crows, are capable of moving the virus to new locations,"said McLean.

The USGS will continue to focus on collecting information that will help determine the extent of the wildlife species involved, the geographic and temporal distribution of the virus, and whether the disease is continuing to expand to new sites.

McLean emphasized that with so many state and federal agencies involved in the West Nile investigation, he is optimistic that scientists will learn what role migratory birds may play in determining if the West Nile viruswill find a permanent home in the western hemisphere and what impact it will have on our native species.

Periodically, the USGS issues Wildlife Health Alerts to keep natural resource agencies appraised of wildlife health or disease issues that may threaten free-ranging and captive wildlife. USGS, along with several state and federal and local natural resource, public and animal health agencies,is diligently monitoring the spread of the virus by conducting field investigations, processing wildlife specimens, and keeping these agencies informed through the USGS Wildlife Health Alerts.

The USGS is also developing digital maps to monitor the expansion and range of the disease. The maps can be quickly updated and allow scientists to electronically overlay maps showing other pertinent information such as climate, vegetation, bird and mosquito species range for the area being studied.

West Nile virus is closely related to St. Louis encephalitis virus, but generally causes a milder disease in humans, according to information from the CDC. The West Nile virus is transmitted by a mosquito, which acquires the virus when it bites an infected bird for the blood meal needed toproduce mosquito eggs. If the same mosquito subsequently bites a human, it can pass the virus to a human host. Like St. Louis encephalitis, West Nile virus is not transmitted directly from person to person or from birds to persons. This is the first time West Nile virus has been recognized in the United States or any other area of the Western Hemisphere.

For more information on West Nile virus, see the following webpages:

USGS Wildlife Health Alert http://www.umesc.usgs.gov/http_data/nwhc/news/whal9902.html

USGS National Wildlife Health Center http://www.umesc.usgs.gov/nwhchome.html

USGS Biological Resources Page on West Nile Encephalitis http://biology.usgs.gov/mosquito/mosquito.htm

Centers for Disease Control and Prevention http://www.cdc.gov/ncidod/dvbid/arbor/arboinfo.htm

The USGS serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.

Subscribe to receive the latest USGS news releases.

**** www.usgs.gov ****

Links and contacts within this release are valid at the time of publication.


Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.usgs.gov/newsroom/article.asp?ID=1195
Page Contact Information: Ask USGS
Page Last Modified: 10/14/2005 1:40:26 PM