Louisiana Horse Tests Positive for Both EEE, WNV

Louisiana Horse Tests Positive for Both EEE, WNV

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A 2-year-old horse residing in Maurepas in Livingston Parish, La., has reportedly tested positive for both Eastern equine encephalitis (EEE) and West Nile virus (WNV) and was humanely euthanized by a local veterinarian.

Commissioner Mike Strain, DVM, with the Louisiana Department of Agriculture and Forestry, is strongly advising horse owners to vaccinate their animals for EEE and WNV. Reports indicate that the horse was not vaccinated.

“Heavy rainfall, which we’ve had in recent weeks, creates a breeding ground for mosquitoes which can carry both EEE and WNV,” said Strain. “Just like humans, horses are infected the same way—by being bitten by infected mosquitoes. I urge horse owners to get their horses vaccinated. Contact your local veterinarian regarding proper vaccination protocols.”

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%.

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.

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

By the same time last year, there were seven cases of WNV and 10 cases of EEE in Louisiana horses.

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