West Nile virus (WNV) remains a threat to horses. But with the right vaccine and preventive measures, horse owners can help protect their horses against this life-threatening disease.

West Nile encephalomyelitis is an inflammation of the central nervous system that is caused by an infection with WNV. It is transmitted by mosquitoes—which feed on infected birds or other animals—to horses, humans, and other mammals.

Horses in (http://www.thehorse.com/articles/32089/grimes-co-texas-horse-tests-positive-for-wnv) Texas and Ohio have tested positive for WNV, the first equine cases reported in the United States this year. In 2012, when 690 cases were reported nationwide, only eight states (Alaska, Delaware, Hawaii, Kansas, Maine, New Hampshire, Rhode Island, and West Virginia) had no reports of equine WNV.

Vaccination remains the most effective way to help protect horses against West Nile and other encephalic or mosquito-borne diseases, such as Eastern equine encephalomyelitis and Western equine encephalomyelitis. Already this year, 14 cases of Eastern equine encephalomyelitis have been reported in Florida and Georgia.

In conjunction with vaccination, use good techniques for managing mosquitoes. This includes:

  • Destroying any mosquito breeding habitats by removing all potential sources of stagnant water; and
  • Cleaning and emptying any water-holding container, such as water buckets, water troughs and plastic containers, on a weekly basis.

Remember that WNV does not always prompt signs of illness. Horses that become clinically ill from the virus can suffer a loss of appetite and depression due to