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West Nile Virus Information Sheet
West Nile Virus (WNV) is a
neurologic disease that first appeared in the Western Hemisphere
in the fall of 1999, causing illness and death in horses, birds
and humans. The
virus is spread by the bite of an infected mosquito and is
harbored by birds, which have assisted in the disease’s spread
from its original epicenter in New York to other areas over the
past three years. WNV
has been recognized in 27 states.
Symptoms usually appear mainly in
the late summer and fall, however some believe it could become a
year-round cycle in warmer climates. The last count of confirmed equine cases in the United
States was 738. Initially it was estimated that WNV would spread across the
U.S. within four years, but many scientists think that it might
move faster.
Clinical
Signs of WNV:
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Flu-like signs, where the horse seems mildly
anorexic and depressed.
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Muscle twitching or weakness.
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Hyperesthesia or Hypersensitivity. Affected horses startle easily, or seem “jumpy”.
Some seem unwilling to be touched or handled and may
respond with aggression.
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Changes in mentality.
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Occasional drowsiness. Horses can go from being over-responsive to showing no
response to stimulation in a matter of minutes.
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Propulsive walking or wandering (driving forward,
often without control).
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“Spinal” symptoms, including asymmetrical
weakness. They may
also show incoordination on one or both sides.
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Other neurological signs include facial paralysis,
head tilt difficulty swallowing, and the inability to stand up.
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Testing/Treatment/Outcome
West Nile Virus has a 30%
mortality rate. The
majority of horses will get better with extensive supportive
care which is very costly. Advanced stages with paralysis have the higher
probability of not surviving. Horses in about 70% of the Florida cases (where WNV has
hit hardest due to year around warm temperatures) appeared to
make a full recovery, although some had prolonged weakness,
taking several months to return to normal.
Mosquito prevention is an
important factor in reducing the risk of West Nile Virus. Here are some steps to follow:
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House horses indoors during peak mosquito times
(dawn and dusk).
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Avoid turning lights on in the stable during
evening and overnight.
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Place incandescent bulbs around the perimeter of
the stable to attract mosquitoes away from the horses.
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Eliminate areas of standing water, such as
discarded tires, birdbaths, etc. Any stagnant water that has been standing for 4 days or
more is an ideal breeding ground for mosquitoes.
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Use repellants that are approved for horses.
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Use fans on horses in the stable, air movement
deters mosquitoes.
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Fog the stable area in the evening.
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The most effective prevention,
however, is vaccination and as with any new vaccine it should be
given twice, 3-6 weeks apart and boostered yearly, preferably
late spring to early summer.
Please
call us at 608-592-7755 if you would like to schedule an
appointment to have your horse vaccinated or if you would like
to have a booster dispensed to you. Don't hesitate to call our
office if you have any further questions or
concerns.
For more information, some
helpful web sites include www.TheHorse.com/WNV
and http://prevmed.vet.ohio-state.edu/Extension/WestNile/WNV.htm
(this is case sensitive).
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