The Equine Disease Communication Center (EDCC) reported Oct. 25 that the Oklahoma Department of Agriculture four additional West Nile virus (WNV) cases in horses in that state.

The EDCC report said the following equids tested positive for the virus:

• An unvaccinated 8-year-old pony gelding located in Choctaw County showed severe neurologic signs, including leg paralysis, and was euthanized.
• An unvaccinated yearling Quarter Horse filly from Payne County was showed moderate neurologic signs, including hind-limb ataxia.
• An unvaccinated 16-year-old Quarter Horse gelding in Beckham County showed mild neurologic signs and is recovering.
• A 7-year-old Quarter Horse gelding located in Atoka County was showed severe neurologic signs, including hind-limb paralysis, and was euthanized. That horse’s vaccination history is unknown.

The new cases bring Oklahoma’s case total to nine for the year.

West Nile is transmitted to horses and other equids 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 fasciculations; 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%