West Nile Encephalitis

West Nile Encephalitis made headlines in 1999 when the virus showed up in the New York and Connecticut areas. We provide this information for you education. Please let us know if there are other resources we could add or whether these resources are no longer valid.

Crows have been implicated in carrying and transmitting West Nile Encephalitis. The crows can carry the virus which then gets transmitted to mosquitoes after a blood meal and then passed to humans who get bit by infected mosquitoes. Once a bird has been infected, it can only transmit the virus to mosquitoes for about 4-5 days.

Articles on West Nile Virus


Known Carriers/Contractors of the Disease

bird species

American Crow, American kestral, American robin, bald eagle, belted kingfisher, black-crowned night-heron, blue jay, broad-winged hawk, cooper's hawk, fish crow, herring gull, laughing gull, mallard, red-tailed hawk, ring-billed gull, rock dove,sandhill crane, and yellow-billed cuckoo, house sparrow, common pigeon,


Cows, horses, bats

CDC http://www.cdc.gov/ncidod/dvbid/arbor/

Wildlife Damage Control abstracted this information from the Entomological Society of America Newsletter Dec. 1999 volume 22, Number 12. They can be reached at ESA

Forward of: USGS Wildlife Health Alert #99-02B

To: Natural Resource/Conservation Managers
From: Director, USGS National Wildlife Health Center (Bob McLean)
Title: Update on West Nile Virus This is a follow up to the September 29, 1999,
USGS Wildlife Health Alert (WHA #02) notifying state and federal natural resource agencies of the emergence of the West Nile virus in both free ranging and captive birds in the New York City area.

The West Nile virus (WNV) is an arthropod- borne virus that has never been reported in the Western Hemisphere. Birds are the natural hosts for this virus. WNV can be transmitted from birds to other birds and animals, including humans, through the bite of mosquitoes. American crows still appear to be the most susceptible species to this disease. The Centers for Disease Control (CDC) in Fort Collins, Co. have confirmed that 17 native bird species have tested virus positive for WNV; Connecticut has added a Cooper's Hawk as an 18th species.

The specific cause of mortality was not determined for all birds. Except for American crows, most species are represented by few specimens.

The species include: American crow Ring-billed gull Yellow-billed cuckoo Rock dove Sandhill crane* Blue jay Bald eagle* Laughing gull* Black-crowned night-heron* Mallard* American robin Fish crow Red-tailed hawk Broad-winged hawk Cooper's hawk Belted kingfisher American kestrel Herring gull * Captive bird WNV has been diagnosed in birds from New York, New Jersey and Connecticut. Geographically the virus has been detected in birds from central New York (a single crow in Saratoga County), western New Jersey (Hunterdon &Warren Counties), south-central New Jersey (Burlington County), and east to Suffolk County on Long Island and the East Haven area of Connecticut. At this time it is difficult to assess the magnitude of the mortality. While there have been reports of high bird mortality (1000's) in some of the affected areas, mostly American crows, a number of the birds have died from other causes.

Of the 255 specimens tested by CDC only about 55% have tested positive for WNV. The earliest confirmed isolate was from a specimen collected on August 9, 1999 in Nassau County, NY. The USGS National Wildlife Health Center, along with CDC and state and federal agencies, are continuing to carry out a national surveillance effort to document bird mortality. We are particularly interested in receiving reports of sick or dead birds with neurological symptoms from states along the Atlantic seaboard. Specimens collected during this surveillance will be examined by USGS at the National Wildlife Health Center and tested for the presence of WNV. Concurrently, USGS, along with several state and federal natural resource and public health agencies, and other interested groups, are continuing to conduct field investigations in the area of the outbreak. The investigation will continue to focus on collecting information and samples that will help determine the extent of wildlife species involved, the geographic and temporal distribution of the virus in bird populations, and if the range of the virus is expanding beyond the currently reported sites.

For further information and to report sick or dead crows or other unusual bird mortality, please contact USGS Wildlife Disease Specialists Drs. Linda Glaser (608-270-2446, linda_glaser@ usgs.gov) or Kathryn Converse (608-270-2445, kathy_converse@usgs.gov).


Extent of Disease

It has been found in Massachusetts, Connecticut, New York and New Jersey.

West Nile Virus Found in Bats


ALBANY, Aug. 30, 2000 -- The New York State Department of Health's Wadsworth Laboratory today confirmed West Nile virus infection in three bats which had been previously submitted for testing. Although it is known that the virus can infect small mammals such as cats and dogs, as well as large mammals, the virus never before has been isolated from bats. The bats, members of the species called "Big Brown bats," were captured in homes in downtown Albany and sent to the Department of Environmental Conservation's Wildlife Pathology Unit (WPU). Because of concerns about possible rabies exposure to the homes' residents, the animals were euthanized and submitted to the State Health Department's Rabies laboratory. Specimens also were submitted by the WPU to the State Health Department for West Nile virus testing.

"This is another clear indication that there are still many more questions than answers about how West Nile virus is establishing itself in the Western hemisphere," State Health Commissioner Antonia C. Novello, M.D., M.P.H., Dr.P.H. said. "Scientists are still learning about the extent of the reservoir for the virus and about the interplay
between species. The bottom line, of course, remains the potential threat to human health."

Health officials stress that bats infected with West Nile virus cannot transmit illness to humans. Like birds and mammals, however, they can themselves be infected through mosquito bites. It is unclear what part bats may play in the West Nile virus reservoir. In the Western hemisphere, native species of birds are particularly vulnerable to West Nile, and dead bird sightings often indicate that the virus is present in a specific area.

Unlike birds, bats will not be routinely tested for West Nile infection by the State Health Department. Instead, some of the
approximately 3,500 bats that are annually submitted for rabies testing will be retained for West Nile virus testing at a later date, as part of continuing research. Dead bird surveillance and testing, on the other hand, is a very sensitive indicator of West Nile virus and dead bird testing is regularly conducted to assess the scope of West Nile's presence throughout New York State.

As of today, West Nile virus has been confirmed in 49 of the State's 62 counties and it is believed to be endemic throughout New York State. Five human cases have been identified, as well as 412 infections in birds, 171 infected mosquito pools and one equine case.

Additional Update Info: On August 29, the New York State Department of Agriculture and Markets announced that a 26-year old horse on Staten Island was euthanized on August 20 after falling ill on August 17 with signs of muscle tremors, an inability to rise without assistance, and evidence of kidney failure. The euthanized horse tested positive for
West Nile virus. This is the first confirmed case this year of equine encephalitis related to West Nile virus. Last summer, 25 horses (9 of which died or were euthanized) on Long Island were found to have evidence of West Nile virus.

New York City issued a Press Release on August 30 saying that a 52 year-old man from the Graniteville section of Staten Island tested positive for West Nile virus. He is significantly younger than the others hospitalized with WNV this year, but details about any pre-disposing medical conditions have not been released. The individual became ill with symptoms of meningitis on August 15, and was admitted to a local hospital on August 18. The patient was released from the hospital on August 25 and is now at home recovering. The laboratory results were obtained by tests performed at the New York
City Department of Health's laboratories, and specimens have been sent to the U.S. Centers for Disease Control and Prevention (CDC) for further confirmation. Full text of the NYC DOH PR:

August 31, 2000 summary the total number of West Nile virus-positive specimens in New York State in year 2000: 440 birds, 172 mosquito pools, 1 sentinel chicken, 6 live wild birds, 3 bats, 1 horse and 6 human cases. WNV has now been detected in 50 of the 62 counties in NYS. The most recent additions to the list of counties where WNV has been
detected: Montgomery, Schoharie and St. Lawrence were added August 30; Steuben County was added August 31. NYS DOH released a current map of detections by county on August 31, best accessed from the DOH WNV index
page: <<http://www.health.state.ny.us/nysdoh/westnile/index.php>http://www.health.= state.ny.us/nysdoh/westnile/index.php.

111 Species Affected by West Nile Mon Sep 9, 1:53 AM ET By ALLISON SCHLESINGER, Associated Press Writer

PITTSBURGH (AP) - The West Nile virus, first spotted in this country in a sick crow three years ago, has now attacked at least 111 species of birds, including the bald eagle and the endangered Mississippi sandhill crane.

The spread of the virus has surprised and alarmed wildlife researchers because it has happened so quickly. Last year, West Nile had been detected only in about a dozen species of birds.

This year, hundreds of birds of prey, particularly red-tailed hawks and great horned owls, have been found dead in the upper
Midwest, said Kathryn Converse, a wildlife disease specialist with the U.S. Geological Survey ( news - web sites)'s National
Wildlife Health Center in Madison, Wis.

About 400 owls and hawks died in Ohio alone in what one wildlife official called "a major die-off." The carcasses were being tested for West Nile virus, which has been confirmed in several cases.

West Nile also has killed such birds in the wild as the ruby-throated hummingbird and Canada goose, and exotic and captive species such as the macaw and the Chilean flamingo, according to the Centers for Disease Control and Prevention ( news - web sites) Web site.

Of particular concern are the deaths of any endangered species, like the Mississippi sandhill crane, which numbers only about 120. It is one of six types of sandhill crane.Since 1999, the virus has also killed at least one bald eagle, a threatened species, according to the CDC Web site."We don't know of any birds that can't be affected by the virus," Converse said.

It's impossible to know exactly how many birds have died from the West Nile virus, wildlife officials say, because the only way to confirm the virus in birds is to test them after they die.

Also, federal agencies like the CDC and Geological Survey rely on state and county health officers to report the bird deaths. But those officials are mainly interested in birds only as a tip-off that mosquitoes carrying the virus have shown up in their areas, so that people can be warned.

News that the virus is spreading in bird populations is frustrating for bird caretakers like James Mejeur, curator at the National Aviary in Pittsburgh, because the illness is hard to detect, treat and prevent.

Although veterinarians are experimenting with a vaccine approved for horses, the most effective way to prevent birds from getting sick is to control the mosquito population, Mejeur said. Some institutions with captive bird populations install mosquito netting. "It's manageable for us because the majority of our bird population is inside," said Mejeur, whose facility has lost three magpies and a crow this year. "But it is a tough time for zoos and other places that can't control the mosquitoes and have large populations of birds."

The horse vaccine has not been widely tested on birds, but the few facilities that have tested it found the birds were not harmed by it, Mejeur said.Still, birds must be injected three times over a span of three months, which can be traumatic to wild populations, he said.At the Raptor Center at the University of Minnesota, caretakers suspect the raptors may have the virus when they develop tremors, a blank stare and confusion. But other illnesses can cause similar symptoms, said Pat Redig, the center's director.At that point there's not much veterinarians can do but give the animals fluids, antibiotics and special feedings that may help their immune systems.

But many raptors infected by the virus die after symptoms appear, said Redig. The Raptor Center has been studying and caring for eagle, hawk, owl and falcon populations since 1974. There is hope that hawks, crows and other birds will become resistant to the virus over time."But we don't know how long that will take and how many raptors we'll lose in the meantime," Redig said.




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