Photo: Gbohne/Wikimedia Commons

Idaho has reported its seventh confirmed case of West Nile virus (WNV) in horses in that state, the Equine Disease Communication Center (EDCC) announced Oct. 10.

The Idaho Department of Agriculture said the yearling Quarter Horse filly with no vaccination history began showing signs of disease on Sept. 16, the EDCC said; clinical signs included facial nerve deficits and ataxia (incoordination) in all four limbs. The EDCC said the filly is responding to treatment.

West Nile is also 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. There are no specific treatments for WNV, however supportive care can help horses recover in some cases. Equine mortality rate can be as high as 30-40%