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Vaccinate
Horses for West Nile Virus and Other Diseases
Auburn, Aug 30, 2002
--- Horse owners should have all their animals vaccinated
immediately for West Nile virus. In 2002, there have been nine
confirmed cases of WNV in horses in Alabama.
"Horses are
affected by WNV more often than other domestic animals," says
Dr. Tony Frazier, the state veterinarian. "The simplest way to
ensure their horses do not contract this potentially deadly disease
is to have the animals vaccinated."
The U.S. Department of
Agriculture issued a conditional license for an equine WNV vaccine
late last summer. Conditional licensing means that the product has
been shown to be safe, pure and have a reasonable expectation of
efficacy in preventing illness caused by WNV.
Frazier, whose office is
a division of the Alabama Department of Agriculture and Industries,
says horse owners should have their animals revaccinated even if
they were inoculated last fall.
"Since this is a
new vaccine, it's not firmly established how long the vaccination
will last," says Frazier.
Dr. Cindy McCall, an
animal scientist with the Alabama Cooperative Extension System, says
the vaccine will only be available from veterinarians.
"The vaccine
manufacturer recommends giving two intramuscular doses three to six
weeks apart," says McCall.
McCall says the vaccine
may be more expensive than the more routine vaccinations given to
horses.
"Cost may be
higher, but that's not really surprising," says McCall.
"There is only one manufacturer, and they probably have not
brought their production up to full capacity yet."
WNV was first identified
in the United States in 1999 in New York and has been spreading for
the last two years. It is a mosquito-borne virus that can cause
encephalitis (an inflammation of the brain) in animals and sometimes
in humans. The virus is spread by mosquitoes that get the disease
from infected birds.
Many horses infected
with WNV do not develop any illness, but more than 35 percent of
those that became sick in 1999 and 2000 died or were euthanized.
Other livestock and poultry do not commonly show illness if infected
with WNV.
Like humans, horses are
particularly vulnerable to both WNV and Eastern equine encephalitis.
Last year in Alabama, more than 160 horses were screened for both
diseases.
In 2001, there were four
equine cases of WNV in Alabama. Three of the animals made full
recoveries, but one had to be euthanized as a result of the disease.
In neighboring Florida, there were more than 450 horses infected
with WNV.
EEE was identified in 15
Alabama counties, primarily across the southern part of the state.
Thirty-six horses tested positive for EEE in 2001.
McCall says there is
little reason for a horse to contract EEE because there is a safe
and inexpensive vaccine available.
"Horse owners in
Alabama should vaccinate their horses twice a year for EEE or
sleeping sickness," says McCall. She adds that the best time to
revaccinate is mid to late summer, such as in August when some cases
of EEE are seen in Alabama. Revaccinating before this time will
increase protection against the disease.
Frazier agrees,
"Owners should get EEE boosters now for their horses and again
in six months."
"EEE is far worse
than WNV in horses," says Frazier. "The mortality rate of
horses infected with EEE is over 90 percent, and from what we know
about WNV, the mortality of infected horses is about 30 to 40
percent."
EEE is almost always
fatal in horses and is characterized by the progressive failure of
the horse's central nervous system.
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