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Equine Veterinarian Lucinda Earven pulls a blood test on a client’s horse while talking about West Nile Virus, a potentially fatal mosquito-borne illness that causes neurological problems in horses.

WHETSTONE — West Nile Virus first arrived in the U.S. in 1999.

“Within two years, it had spread across the country,” recalls Veterinarian Devon Kartchner of Farm & Ranch Veterinary Service, a mobile practice for horses, cattle and other livestock. “Birds are the carriers, or reservoir, but mosquitoes are the vectors. If a mosquito bites an infected bird, it can transmit the disease to horses, humans or other mammals. So, anywhere there are mosquitoes, there is also potential for this virus.”

While West Nile Virus is potentially fatal to horses, it is preventable through proper vaccination, Kartchner said.

“It’s easy to vaccinate and needs to be done every year. I recommend the vaccination to all my clients with horses because it’s a safe, effective type of prevention.”

Veterinarians recommend vaccinating between the spring and early summer — sometime around April through June — to give horses plenty of time to build up immunity.

It takes between 10 days and two weeks for horses to build immunity against the virus once vaccinated, so it’s best to vaccinate prior to peak mosquito season in September and October, said equine Veterinarian Lucinda Earven, whose mobile practice is Earven Equine Veterinary Services.

“If you have unvaccinated horses, it’s best to get it done now, before more time goes by. We’re so fortunate there is a vaccine for horses, so most equine vets advise their clients to take advantage of it.”

West Nile virus is spread between birds by mosquitoes. Horses and humans are considered dead-end hosts and do not contribute to the transmission cycle.

“The virus can not be transmitted from horse to horse or horse to human. It’s transmitted by infected mosquitoes,” Earven said.

Earven said she mails vaccination reminders to her clients every spring and fall and an overwhelming number of her horse owners want their animals vaccinated.

“It’s good, preventative medicine, yet there’s no treatment for the disease if a horse comes down with West Nile,” Kartchner said. “Horses receive supportive care and you hope for the best. Even though horses can survive the virus, the disease course can get serious very quickly.”

Horses with symptoms of West Nile Virus often exhibit a range of neurologic problems.

“Anytime you have a neurologic horse, it’s very difficult to manage, no matter the cause,” Kartchner said. “That’s why the vaccine is so important.”

Both Kartchner and Earven include West Nile Virus on their list of core vaccines and recommend it for all their clients’ horses.

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