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West Nile Virus


Information on West Nile Virus changes rapidly. Here is some basic information accurate at the end of 2002 followed by links to further resources that may have been updated more recently.

When did it first occur? What is the current range WNV.
It first appeared in New York City in the summer of 1999. The first outbreak was centered in Queens, NY, but also detected in other locations within a 75-mile radius of New York City (in NY, NJ and Connecticut).

By the end of 2002 it had been reported in all but 6 states - Alaska, Arizona Hawaii , Nevada, Oregon and Utah. Plus five Canadian Provinces.

Symptoms and human mortality
As of Dec 19, 2002 - Center for Disease control reported 3,852 human cases with 232 fatalities from 39 states and Washington D.C.

Incubation: 3-14 days after being bitten by an infected mosquito

Most people infected show no symptoms

West Nile Fever -
Fever, headaches, body aches, swollen lymph glands and in some a body rash.

West Nile Virus
About 1 infected person in 150 becomes seriously ill with central nervous system infection (encephalitis &/or meningitis) - severe headache, weakness, high fever, neck stiffness, disorientation, tremors, convulsions, paralysis and coma.

Bird Mortality
More than 140 bird species reported with West Nile Virus

- chickadees, doves, grackles, gulls, herons, kingfishers, pelicans, sparrows, swans, turkeys, warblers, woodpeckers and wrens.

- Natural immunity protects some individuals

- Past fall significant impact on raptors, will this lead to an increase in rodent populations?

- Spread to the winter tropics range where mosquitoes are active year around.

Mortality in other species
- 14,000 horses reported infected in the past year

- Other mammals including reindeer, squirrel, wolf, cat, dog, mountain goat and sheep, black bears

- Harbor seal at the New Jersey State Aquarium died of the disease

- In zoos - penguins, seals, emus and flamingos

- Florida alligator farms lost 200 + alligators from the disease

How is it spread?
- WNV is transferred via the bite of several species of mosquito. It is typically spread back and forth - mosquito to bird - bird to mosquito - mosquito to another bird.

- Occasionally the virus does spread from mosquito to mammal, such as humans or horses.

- Raptors can acquire the virus by eating infected prey

- Some birds can apparently spread the virus in their droppings.

- There's also evidence that some birds can pass the virus directly to their chicks while they're still inside the egg.

- West Nile virus can be transmitted directly from adult mosquitoes to their eggs, so that newly hatched aquatic larvae are born infected.

- The virus can persevere through the winter, even in many Northern states. Winter host unknown, allows the disease to spread year round and earlier each year.

- 36 mosquito species carry the virus.

- Handling of infected birds with cuts

- Mother to unborn child

Prevention
- eliminate potential breeding areas for mosquitoes

- wear long sleeve shirts and pants as well as mosquito repellent

Vaccine
- A horse vaccine has been available in some areas for about a year and is proving to be very effective

- The horse vaccine was tested on birds and proved not to be effective

- In November, veterinarians at the Los Angeles and San Diego zoos injected condors an experimental vaccine to try to confer immunity before the spring egg-laying season. Results look positive so far.

- Human vaccine may be available for testing in mid to late 2003.

Resources:

National Wildlife Health Center

Center for Disease Control

The American Birding Association also published an informative article 2002.


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