Posted: 09.26.2011

The mosquito-borne disease strikes the horse’s central nervous system and has a mortality rate of 90 percent or higher. It has been detected in Price, Lincoln, Taylor, Clark, Marathon, and Dunn counties to date.

He advised horse owners to call a veterinarian if their horses show any signs of central nervous system disease: depression, loss of appetite, drooping eyelids and lower lip, aimless wandering and circling, blindness and sometimes paralysis.

“EEE looks a lot like other diseases of the central nervous system – other strains of encephalitis, West Nile virus, equine herpes virus-1, even rabies,” Ehlenfeldt said. “That’s why it’s important that you call a vet and get a definite diagnosis if possible. You need to know if other animals are at risk, or if there’s a human health risk, because the same mosquitoes that infect horses may infect humans in some cases.”

More cases are likely to be confirmed, Ehlenfeldt said. He noted that fairly warm weather is predicted for next week that might allow mosquitoes to be active. The risk remains until overnight temperatures routinely fall below freezing. In addition, some preliminary results are still awaiting confirmation at the National Veterinary Services Laboratories.

It may be too late for initial vaccines to be effective, because it takes several weeks for immunity to build up. But boosters are effective in a matter of days for horses that have already been vaccinated, so owners should consider that option. Owners should also eliminate any standing water that they can, and keep horses in the barn between dusk and dawn if possible, to limit their exposure to mosquitoes.

Wisconsin last experienced a large-scale outbreak of EEE in 2001, when 69 cases were confirmed. Since then, cases have occurred sporadically

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