The first appearance of West Nile virus in North America occurred in 1999, with encephalitis reported in humans and horses, and the subsequent spread in the United States.  As of May 2006, West Nile virus has been documented in the contiguous United States and the District of Columbia.

The Colorado Department of Agriculture recommends vaccinations for horses in an effort to stay vigilant against West Nile Virus (WNV).

In 2006, more than 1,000 cases of WNV were reported in horses nationwide.  West Nile Virus can cause an inflammation of the brain and spinal cord.  Mosquitoes transmit the disease and infected horses may display symptoms including head tilt, muscle tremors, stumbling, lack of coordination, weakness of the limbs or partial paralysis. 

Horses that have been vaccinated in past years will need an annual booster shot.  However, if an owner did not vaccinate their animal in previous years, the horse will need the two-shot vaccination series within a three to six week period.

In addition to vaccinations, horse owners also need to reduce the mosquito populations and their possible breeding areas. Recommendations include removing stagnant water sources, keeping animals inside during the bugs¿ feeding times, which are typically early in the morning and evening, and using mosquito repellents.

The Department¿s Rocky Mountain Regional Animal Health Laboratory can test equine serum for West Nile Virus. The fee is $6.75 per sample with results within 48 hours. Samples must be sent to CDA-RMRAHL, 2331 W. 31st Ave., Denver, Colo., 80211.  For more information on the test, call the Lab at (303) 477-0049.

If horse owners have questions or see symptoms of WNV in their horses, they are urged to contact their local veterinarian. 

For more information on West Nile Virus, visit the Colorado Department of Public Health and Environment.