West Nile Virus Still a Threat to Horses

West Nile Virus Still a Threat to Horses

With the right vaccine and preventive measures, it's not too late for horse owners to help protect their horses against this life-threatening disease.

Photo: Erica Larson, News Editor

West Nile virus (WNV) remains a threat to horses. However, with the right vaccine and preventive measures, it's not too late for horse owners to 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. As of Sept. 3, 33 states have reported 186 cases of WNV in horses, with Louisiana and Texas having the most confirmed cases--26 and 16, respectively.

The number of reported WNV cases fell from 1,069 in 2006 to 146 in 2010, and the decline is said by health experts to reflect both vaccination and naturally acquired immunity.

"It is a good sign that the number of cases has declined over the last decade; however, there has been an increasing number of both human and equine cases, especially over the last couple months," said Tom Lenz, DVM, MS, senior director of equine technical services for Pfizer Animal Health.

Vaccination remains the most effective way to help protect horses against West Nile and other encephalic or mosquito-borne diseases, such as Eastern and Western equine encephalomyelitis. A trusted vaccine is commercially available to help offer demonstrated protection against WNV, Eastern and Western equine encephalomyelitis, and tetanus all in a single vaccine. According to the American Association of Equine Practitioners guidelines, WNV is considered a core vaccination, along with both Eastern and Western equine encephalomyelitis, tetanus, and rabies.

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 lead to signs of illness. Horses that do become clinically ill, the virus infects the central nervous system and can cause clinical signs such as loss of appetite and depression. Other clinical signs can include fever, weakness or paralysis of hind limbs, impaired vision, ataxia, 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%.

No matter the location, horses can be at risk. By providing proper vaccination and helping to manage mosquito populations, horse owners can do their part to help prevent WNV infections.

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Pfizer Animal Health

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