Colorado animal health officials have confirmed the state's first reported equine case of West Nile virus (WNV) for 2014 in an Adams County horse.
This case was diagnosed by Colorado State University Veterinary Diagnostic Laboratory in Fort Collins.
Disease transmission from year to year and depends on a number of factors, including mosquito numbers. The WNV can be amplified and carried by infected birds and then spread locally by mosquitoes that bite those birds. The mosquitoes can then pass the virus to humans and animals.
Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); 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%.
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The clinical signs of WNV can be consistent with other important neurologic diseases such as equine encephalitis, rabies, and equine herpesvirus; therefore it is important to work with your veterinarian to get an accurate diagnosis through laboratory testing.
Horse owners should also consult their private practicing veterinarian to determine an appropriate disease prevention plan for their horses. Vaccines have proven to be a very effective prevention tool. 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.