When I moved my horse to Falcon in 2003, the West Nile virus had just hit Colorado in full force, and the first West Nile vaccination for horses had just been developed in 2001.The U.S. Department of Agriculture had confirmed 378 equine cases of West Nile in 2002. It seemed like every horse-related publication carried an article about the virus. At that time, veterinarians were advising horse owners to have their horses vaccinated in the early spring, followed by a booster shot six weeks later.As the number of human and equine cases of West Nile increased, public health departments pulled together plans to control the virus, focusing on mosquito control. Media attention to the problem made the general public more aware of prevention techniques, and horse owners began to routinely vaccinate their horses.The U.S. Geological Survey has kept records of reported cases of West Nile in all states. In 2003, Colorado reported 393 positive veterinary results (99 percent of “veterinary” test results were from horses), and 44 of those were in El Paso County. In 2004, only 31 cases were reported in the entire state, with two in El Paso County.While still a threat to both horses and humans, the incidence of the virus has declined significantly in the past two years. Randy Parker, DVM, of Range View Equine Associates, now typically gives horses only one vaccination a year. “We have a lot more experience with the vaccination now,” says Parker. “We didn’t know when the virus got here, how prevalent it would be, but we had very few cases last year.”Fort Dodge Animal Health, manufacturer of the original vaccination, is now working on a vaccine called West Nile-Innovator(r) DNA, which causes the horse’s cells to begin making proteins from the virus, which in turn triggers an immune response.It’s still important to take precautions to keep the mosquito population from growing. The most important step in accomplishing this is to remove any standing water on your property. Replace the water in buckets and troughs at least every three days, and don’t let water collect in drains, bird baths or puddles. If you can’t remove water, you may need to treat it with Mosquito Dunks, small pellets containing a microbial larvicide that is toxic to mosquito larvae.If possible, horses should be taken inside at dawn and dusk, when mosquitoes feed. This is especially important from August until the first frost, when horses are most likely to be infected. Check with your vet about how to strengthen your horse’s immune system so he can fight off the virus if he contracts it.To monitor current reports of West Nile cases or to see data for previous years, go to http://westnilemaps.usgs.gov/co_veterinary.html.
