||Texas Sees Its First Case of West Nile
Virus in a Horse
Preliminary tests on a sick horse that was euthanized Saturday, June
29, near Katy in far west Harris County, indicate that the animal was
infected with West Nile Virus (WNV), a form of "sleeping sickness" first
detected in Texas in two dead blue jays June 18 on the northwest side
of Houston. According to the Texas Department of Health (TDH), another
29 infected birds have since been found.
"We were notified today (July 3) that tests run on samples of the horses's
blood and spinal fluid were positive for WNV. The tests were run both
at the Texas Veterinary Medical Diagnostic Laboratory (TVMDL) in College
Station, and at the National Veterinary Services Laboratory (NVSL) in
Ames, Iowa," said Dr. Linda Logan, Texas' state veterinarian and executive
director for the Texas Animal Health Commission (TAHC), the state's livestock
health regulatory agency.
"The NVSL is running additional confirmation tests on the blood samples,
but more than likely, we are seeing Texas' first case of West Nile Virus
in a horse. Diagnosing WNV must be based on laboratory confirmation, as
the signs of the disease, including staggering or the inability to rise,
can mimic other diseases, including rabies, or other encepalitic diseases,
such as Western Equine Encephalitis (WEE) and Eastern Equine Encephalitis
WNV was unheard of in North America until l999, when it was detected
in birds in New York. The virus, which can cause brain swelling and severe
illness in horses, previously had been confined to Africa, Europe, Asia,
and the Middle East. WNV has spread to 20 US states, following the migratory
flight patterns of birds along the Eastern Seaboard and west as far as
Texas. In 2001, 738 horses, donkeys or other members of the equine family
were diagnosed with the disease in the U.S., and about 20 percent of the
animals had to be euthanized, due to the severity of their illness.
"Blue jays, crows and more than 70 other species of birds can carry the
virus, but it is the mosquito that puts the disease cycle in motion,"
explained Dr. Logan. "After feeding on infected birds, mosquitoes ingest
the virus, and about one percent of the pests then become infected and
capable of spreading the virus to horses or humans. There have been no
documented cases of animals or humans spreading the disease. Dogs and
cats appear to be resistant to the disease."
"Home and stable owners should take precautions to prevent mosquito bites,"
said Dr. Joe Garrett, a veterinarian with the TDH's Zoonosis Control Division.
"Get rid of stagnant water, drain flowerpots, keep bird baths clean and
cut weeds down to discourage mosquito breeding grounds. Apply insect repellents,
and put up screens to protect your home or stable from being 'invaded'
by mosquitoes. There is no vaccine for people, but fortunately, human
cases of WNV are extremely rare. However, see your physician immediately
if you develop signs of the disease, which include fever, headache, body
aches and swollen lymph glands. More severe infection may be marked by
headache, high fever, neck stiffness."
"We continue to work with other agencies to urge horse owners to have
their animals vaccinated against WNV, and with the diagnosis of this disease
in the Houston area, all possible preventive efforts are import to stop
the spread of this disease," said Dr. Richard Ferris, area-veterinarian-in-charge
for the U.S. Department of Agriculture's Veterinary Services in Texas.
"We are investigating other potential cases in horses in Harris County
and are awaiting test results. If you live in the Houston area, protect
your horses from mosquitoes. While a vaccine is available for horses,
the animal must receive two doses of WNV vaccine three to six weeks apart,
and full protection does not begin until at least four to six weeks after
the second dose of vaccine is administered," he said. "I'd urge owners
to take action now to get horses protected."
"If your horse becomes ill and goes off feed, sways, develops head tremors,
muscle twitches or cannot rise, contact your veterinarian, so he or she
can collect and send in samples to us for diagnostic testing," said Dr.
Lelve Gayle, executive director of the TVMDL. Laboratory confirmation
of cases is particularly important for tracking the movement of WNV within
the state. Dr. Garrett said the TDH is continuing its WNV disease surveillance
statewide, which includes testing mosquitoes, dead crows, blue jays, hawks
and sampling zoo birds. Dead crows, blue jays or hawks can be submitted
for laboratory examination, by calling the nearest regional Texas Department
of Health office or the Texas Department of Health in Austin at 1-512-458-7255.
"If you are picking up a dead bird, wear gloves and wash your hands afterward,"
explained Dr. Garrett. "The bird could have had parasites of other illnesses,
and it's always advisable to keep a barrier---like gloves--between you
and the dead bird."
Dr. Logan reminded livestock owners that, as always, the TAHC operates
a 24-hour hotline at 1-800-550-8242 for taking reports of unusual signs
in livestock, including:
- staggering, falling, or inability to rise
- illness affecting a large percentage of animals
- sudden death loss
- blistering around an animal's lips, teats or hooves
- unusual ticks or maggots
Additional information about WNV can be accessed on the internet at: