Horse Dies of Rare Encephalitis Virus

Public health officials are warning that a horse in the Moorpark area died last month of a form of encephalitis that is rare in the West, but could lead to a serious, and sometimes fatal, disease in humans when transmitted by mosquitoes.

Scientists believe the horse was infected with eastern equine encephalitis virus, the first reported infection west of the Mississippi and Texas.

Mosquitoes that were found near the horse’s stable tested negative for the virus, which leads health officials to believe that the threat to people and other horses in the county is minimal.

“For the spread of this disease to occur there has to be widespread infection of mosquitoes and birds,” said Dr. Robert Levin, a county public health officer. “We have demonstrated that this is simply not the case right now in our county.”

Officials said they were not sure where the horse contracted the virus, but it had appeared at shows in Utah and two other locations in California in the weeks prior to its death. In addition, the horse, and 27 others in the stable had been inoculated the week before with a vaccine that included the eastern equine encephalitis virus. None of the other horses have become ill.

The county environmental health department has year-round mosquito-control programs to regularly clear channels, streams and creeks.

It is recommended that residents concerned about mosquitoes drain all standing water on their property and wear protective clothing and insect repellent before engaging in outdoor activities where mosquitoes might be present.

Officials said they are continuing to investigate the source of the horse’s infection.