West Nile Virus is the leading cause of encephalitis in horses and humans in the United States. In 2009, Arizona had 20 human West Nile cases and no horse cases. During 2010, the number of cases increased dramatically with 164 human cases, 12 of which resulted in death, and 5 horses also tested positive for the disease.
Our practice diagnosed and treated two of those West Nile cases which both resided in Apache Junction. One horse, with an unknown vaccination history, exhibited neurologic signs in late October and unfortunately had to be euthanized. The second horse was vaccinated for West Nile in the spring of 2010 and contracted the disease in late November. This horse survived after extensive treatment. With the late surge of West Nile in 2010, we feel our clients should take special precautions this spring against this deadly disease.
There are several key points to consider with West Nile Virus:
• Horses in irrigated and non-irrigated regions of the valley are at risk of contracting
West Nile Virus.
• Vaccinated horses have a much higher survival rate than unvaccinated horses.
• Do not postpone having your horses properly vaccinated.
• Eliminate all standing water in your horse’s environment.
• Use fans in stalls to help deter mosquito travel.
• Do not leave barn lights on overnight.
• A topical mosquito repellant can be helpful.
• There is no known horse to horse or horse to human transmission.
