INDIANAPOLIS (1 November 2001)--A North Central Indiana horse has tested positive for the West Nile virus. This animal marks the first confirmed equine case reported in Indiana.

Blood and tissue samples from the 7-year-old mare were submitted to the USDA's National Veterinary Services Laboratory in Ames, Iowa for testing after the animal was euthanized. The mare began exhibiting unusual clinical signs two weeks ago.

West Nile virus is a mosquito-borne organism that causes encephalitis, or inflammation of the brain. A horse infected with the disease will typically show clinical signs such as listlessness, stumbling and incoordination, weakness of limbs, ataxia, partial paralysis or death.
Fever is not generally observed. Symptoms of West Nile are similar to other diseases of the central nervous system, such as Eastern Equine Encephalitis, Western Equine Encephalitis and St. Louis Encephalitis. Mosquitoes spread the West Nile virus by feeding on infected birds, then biting people or horses. Horses and people are dead-end hosts; the virus cannot be spread from man-to-horse, horse-to-man, man-to-man, or horse-to-horse.

According to Dr. Sandra Norman, Director of the Indiana State Board of Animal Health's Equine Division, the infected horse was one of two equine on the farm. Neither animal had travelled outside the state in recent months; therefore, exposure likely occurred on the home farm. Although the second horse on the premise appears healthy, BOAH veterinarians collected blood samples for testing for exposure to the virus. Most horses infected with the West Nile organism can recover with supportive care and treatment. Recovered animals do not pose a threat to other animals or people, and do not need to be destroyed. In August, USDA granted conditional approval for a West Nile virus vaccine for use in all equine. "Conditional approval" means the product has been shown to be safe, pure and have a reasonable expectation of efficacy in preventing illness. Two doses must be administered 3 weeks to 6 weeks apart, then boostered annually thereafter. The vaccine is readily available only through licensed veterinarians.

Although the season for mosquito activity is waning, Dr. Norman encourages horse owners to continue to be vigilant in minimizing their animals' exposure to the insects and eliminating potential pest breeding sites. Until 1999, West Nile virus was not known to exist in North America. Since the disease was identified in New York three years ago, the virus has killed 12 humans and resulted in the deaths of more than 30 horses (some due to euthanasia). Officials with the Indiana State Department of Health have reported 44 positive birds in seven Indiana counties this year. Anyone who notices clinical signs consistent with West Nile virus in their animals should contact a local veterinarian for further diagnosis. Anyone finding a dead crow or blue jay should contact his/her local health department to submit the bird for testing. (State laboratory officials will not accept other bird species for West Nile virus testing at this time.)

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