It’s that time of year again. West Nile virus (WNV) has been detected in mosquitoes in Salt Lake County, Utah. Now is the time for area horse owners to call their veterinarian for appropriate vaccinations for your work, pleasure, and companion equine partners.

West Nile is transmitted to horses via bites from infected mosquitoes. Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculation; hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia. Equine mortality rate can be as high as 30-40%.

There are a multitude of vaccinations available for equids, but that doesn’t mean your horse needs all of them. It is best to develop a program or plan with your local veterinarian that reflects what your animals’ specific needs are based on risk of disease even if you vaccinate them yourself. Some basic parameters to consider are the animal’s use, location, age, and lifestyle, such whether they travel to shows and other venues or remain on the ranch or farm.

The American Association of Equine Practitioners (AAEP) considers several vaccines “core,” meaning nearly all horses should receive them each year. These vaccines include those that protect against tetanus, Eastern and Western equine encephalomyelitis, WNV, and rabies. The AAEP considers other vaccines “risk-based.” Veterinarians recommend risk-based vaccines depending on the horse’s region, population, and disease risk. These include: anthrax, botulism, equine herpesvirus type 1 and 4, equine viral arteritis, equine influenza, Potomac horse fever, rotaviral diarrhea, snakebite, and strangles