The number of equine West Nile virus (WNV) cases identified this year in the United States continues to rise as Connecticut, Florida, and Kentucky all reported new cases this week.
Connecticut--According to a Sept. 11 press release from the Connecticut Department of Agriculture, two resident horses tested positive for the virus in late August. Neither horse had a documented WNV vaccination history, the release said.
A 4-year-old horse from Southbury became lethargic and began stumbling on its front fee Aug. 27, the release said. The animal's clinical signs progressed to include fever, depression, and ataxia (incoordination), the release read, and a positive WNV test result was returned shortly thereafter. The horse has been under veterinary care and is currently recovering, the release said.
Meanwhile, on Aug. 29, the owner of a 31-year-old horse from South Windsor found the animal recumbent and unresponsive. As the animal's condition continued to deteriorate, he was euthanized by a veterinarian. Test results later confirmed WNV.
WNV is transmitted to horses and humans via mosquitoes. "Horse owners should review their animals' vaccination records with their veterinarians to ensure that WNV and Eastern equine encephalomyelitis (EEE) vaccinations are current and their horses are protected during the mosquito season," said Mary Jane Lis, DVM, MS, PhD, state veterinarian for the Connecticut Department of Agriculture.
Florida--Also on Sept. 11, the Palm Beach County, Fla., Health Department announced that a Loxahatchee horse euthanized last week was confirmed positive for WNV. "This is the second horse statewide to be reported with WNV infection with onset during 2012," a news release said.
Kentucky--Finally, Kentucky animal health officials announced the commonwealth's tenth case of equine WNV in 2012, according to a Sept. 11 statement from Kentucky Equine Programs Manager E.S. "Rusty" Ford.
The affected horse--a yearling Quarter Horse filly from Metcalfe County--presented with mild ataxia, lethargy, and proprioceptive deficits (lack of physical awareness of limbs and their placement) on Sept. 6, Ford said in his statement. The horse received veterinary care and is reportedly improving, Ford said. The filly had no previous WNV vaccination history, he added.
"Nine of the 10 cases have occurred in horses reported to have occurred in unvaccinated horses or horses not adequately vaccinated," Ford relayed. "Five of the animals have survived."
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%.
The USDA Animal and Plant Health Inspection Service reported 87 cases of WNV in U.S. horses in 2011.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.