Louisiana Horse Owners Warned about EEE, WNV Threats

An increase in Eastern equine encephalitis (EEE) and West Nile virus (WNV) cases in horses has prompted Louisiana Department of Agriculture and Forestry (LDAF) Commissioner Mike Strain, DVM, to warn owners to vaccinate their horses.

"The rain we've been having creates breeding grounds for mosquitoes," said Strain. "If a mosquito bites an infected bird, Eastern equine encephalitis or West Nile can be spread to horses, dogs, cats, even alligators and, of course, humans."

So far this year, the LDAF Office of Veterinary Health is reporting eight WNV and 10 EEE cases in horses. According to the USDA Animal and Plant Health Inspection Service (APHIS), Louisiana reported three EEE cases in horses, but did not report any equine WNV cases.

"Horses are infected the same way humans become infected, by being bitten by infected mosquitoes," said Strain. "We want people to also be mindful of mosquitoes and to take preventative measures to stay safe."

Prevention includes avoiding mosquitoes, using mosquito repellants that are safe for horses and humans, and vaccination for horses. So far, there is no vaccination approved for people.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Its fatality rate in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures. Sixty equine EEE cases were confirmed in the United States in 2011, according to APHIS equine disease surveillance.

Clinical signs for WNV include flu-like 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 (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%. The APHIS reported 83 cases of WNV in U.S. horses in 2011.

Strain advised horse owners to contact their local veterinarian regarding proper vaccination protocol during this time of increased risk.

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