Weather Conditions "Ripe" for WNV Activity

Kentucky Agriculture Commissioner James Comer has issued a warning that weather conditions are ripe for an outbreak of West Nile virus (WNV) and cited Kentucky State Veterinarian Robert Stout, DVM, who advised horse owners to consult their veterinarians about vaccinating their horses against the disease.

"While we do not wish to cause unnecessary alarm, we are concerned about the equine population's vulnerability to this potentially deadly disease," said Comer. "I am confident that Kentucky's equine owners will act in the best interests of their horses and seek guidance on vaccinations."

West Nile is spread by mosquitoes, and mosquitoes thrive in the warm, wet conditions Kentucky has experienced in the last few weeks. No horse in Kentucky that has undergone a full West Nile vaccination regimen is known to have contracted the virus since 2003, according to Stout. West Nile was first discovered in Kentucky in 2001. The commonwealth confirmed 513 equine cases of the disease in 2002 and 102 cases in 2003. Kentucky recorded just one equine case in 2011.

Clinical signs for WNV include flulike conditions where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia, or 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 (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%.

The American Association of Equine Practitioners recommends vaccinating all horses against WNV as a preventative measure. In addition to vaccination, minimize mosquito populations by eliminating breeding and resting areas, and by keeping mosquitoes away from horses. For example, reduce or eliminate sources of stagnant or standing water in close proximity to horses, remove manure from areas near the horses, keep horses stalled during peak mosquito periods (i.e., dawn and dusk), use equine approved mosquito repellents or protective fly gear (i.e., fly masks or sheets), and place fans in barns or stalls to maintain air movement, as mosquitoes don't fly well in wind.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More