The Equine Disease Communication Center (EDCC) reported Oct. 2 that the Iowa state veterinarian has confirmed two new equine West Nile virus (WNV) cases. There have been 12 confirmed cases of WNV in Iowa horses so far this year, according to EDCC data.
“A 2-year old Quarter Horse mare and a 4-year old Quarter Horse mare in Polk County first developed ataxia (incoordination) on Sept. 24,” the EDCC said. “The horses are being treated symptomatically. Neither horse was vaccinated.”
Last year there were two confirmed cases of WNV in Iowa horses, according to USDA Animal and Plant Health Inspection Service data.
West Nile virus is transmitted to horses via bites from infected mosquitoes. Not all infected horses show clinical signs, but those that do can exhibit:
- 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’re daydreaming or “just not with it”;
- Occasional drowsiness;
- Propulsive walking (driving or pushing forward, often without control); and
- Spinal signs, including asymmetrical weakness; and
- Asymmetrical or symmetrical ataxia.
West Nile has no cure, however some horses can recover with supportive care. Equine mortality rates can reach 30-40%.
Studies have shown that vaccines can be effective WNV prevention tools. Horses vaccinated in past years need an annual booster shot, but veterinarians might recommend two boosters annually—one in the spring and another in the fall—in areas with prolonged mosquito seasons. In contrast, previously unvaccinated horses require a two-shot vaccination series in a three- to six-week period. It takes several weeks for horses to develop protection against the disease following complete vaccination or booster administration.
In addition to vaccinations, owners should work to reduce mosquito population and breeding areas and limit horses’ mosquito exposure by:
- Removing stagnant water sources;
- Dumping, cleaning, and refilling water buckets and troughs regularly;
- Keeping animals inside during the bugs’ feeding times (typically early in the morning and evening); and
- Applying mosquito repellents approved for equine use.