West Nile Virus - New Treatment Option
A recently introduced antiserum
provides critical antibodies to the West Nile virus
A new weapon against the *West Nile virus in horses was
recently granted a one-year conditional license by the U.S. Department
of Agriculture. The product, a West Nile virus antiserum, does
not prevent infection but instead helps the horse fight off the
virus by delivering antibodies directly and instantly into his
"This antiserum is essentially purified antibodies collected from
hyperimmunized horses," explains Tom Robb, PhD, of Novartis Animal
Vaccines of Kansas, which manufactures the antiserum. "If you
have a horse who contracts West Nile, you can deliver this antiserum
and provide him with antibodies to fight it. We typically see
a marked improvement in the horse within 24 to 36 hours."
Under the conditional license, which is issued after a product
is determined to be safe, the antiserum can be sold while data
on its efficacy are collected. At press time, Robb anticipated
the antiserum would be available in all states.
A West Nile virus vaccine is available, but until now little beyond
intensive nursing could be done for horses who became ill. "We
saw a real need in the horse community for some type of West Nile
virus treatment," Robb says.
What's more, he adds, the antiserum can be used to protect at-risk
horses until vaccination is possible. "If one horse in the barn
comes down with West Nile virus, you might consider giving this
product to other horses until you can get them vaccinated. This
isn't a replacement for vaccination but a treatment to be used
until you can vaccinate."
Available only to veterinarians, the West Nile virus antiserum
is delivered via intravenous infusion. Robb estimates the cost
to horse owners to be $350 or more.
*West Nile virus - a flavivirus transmitted by mosquitoes.
West Nile virus can infect horses, humans, birds and other mammals.
In horses, as in people, infection with the virus usually causes
little or no illness. For reasons not yet determined, however,
West Nile infection sometimes triggers swelling of the brain (encephalitis)
that produces limb weakness, muscle fasciculation (twitching),
incoordination, behavioral changes, paralysis and recumbency.
In severe cases, West Nile encephalitis can lead to coma and death.
Reprinted from: EQUUS - November 2003, Issue
313: Equus staff writer, Christine Barakat
presented in this article is provided for educational and informational
purposes only. Decisions regarding the health and welfare of your
horse or pony should be made only after consultation with a licensed
For your horse's health, it is important that you
develop and maintain a good working relationship with your local
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