COLUMBUS - The number of Ohio horses infected by the West Nile virus has increased more than fourfold in less than a month.

        Ohio Department of Agriculture spokeswoman Melanie Wit said that as of Friday, 524 horses in as many as 76 Ohio counties had the virus. Three weeks ago, 101 had it.

        Holmes County had 114 cases and Wayne County had 80. Agriculture officials said that was largely because of nearby Killbuck Marsh, an ideal home for mosquitoes.

        Dave Glauer, Ohio's state veterinarian, said that just because an animal tests positive for West Nile doesn't mean it's about to die. About 30 percent of infected animals die of the virus, which causes swelling of the brain.

        “The key is to notice any type of unexplained lameness,” he said.

        Among humans, Ohio has five confirmed cases and 307 probable cases of the virus, and it's suspected in 14 deaths, the state Health Department said Friday.

        The number of horses infected with the mosquito-borne virus has increased dramatically this year. Last year, the U.S. Department of Agriculture reported 738 equine cases in 20 states. This year, at least 7,462 horses have it.

        Dr. Glauer said owners who notice a horse is having trouble balancing, seems depressed or is not eating should immediately consult a veterinarian.

        Heidi Immegart, a veterinarian who serves the Delaware County area, said most cases of West Nile found in horses manifest themselves before that. When a horse continually twitches around the muzzle and chin, that's usually a good indication it's been infected. The virus can progress quickly, downing horses sometimes in 48 hours.

        West Nile, although it is not contagious, is treated in horses the same way people are treated for the flu.

        “You take an aspirin and get plenty of rest,” Dr. Glauer said.

        A vaccine for the virus has been available for horses since August.

        So far only three vaccinated horses in Ohio have been infected by the virus.

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