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.
