There has been a recent case of West Nile reported in Idaho September 2015.
If your horse has not been vaccinated or is overdue for vaccination, it’s not too late to help protect it against this life-threatening disease with a booster. July through October coincides with peak mosquito activity in some locations, which can place your horse at the highest risk of contracting West Nile virus (WNV) during this time of year.
A viral disease, WNV is transmitted by mosquitoes—which feed on infected birds—to horses, humans, and other mammals.
Vaccination remains the most effective way to help protect horses against West Nile and other mosquito-borne diseases, such as Eastern equine encephalomyelitis (EEE) and Western equine encephalomyelitis (WEE).
Remember, WNV does not always lead to signs of illness. In horses that do become clinically ill, the virus infects the central nervous system and might cause signs such as loss of appetite and depression. Other clinical signs can include fever, weakness or paralysis of hind limbs, impaired vision, ataxia (incoordination), aimless wandering, walking in circles, hyperexcitability, or coma. Horse owners should contact a veterinarian immediately if they notice signs of WNV infection in their horses, especially if they are exhibiting neurological signs. The case fatality rate for horses exhibiting clinical signs of WNV infection is approximately 33%.
By providing proper vaccination and helping to manage mosquito populations, horse owners can do their part to help prevent WNV infections.