The USDA National Veterinary Services laboratory in Ames, Iowa has confirmed that three horses submitted for testing by the Virginia Department of Agriculture and Consumer Services are positive for Eastern Equine Encephalitis (EEE). Results are still pending on two other horses and another case was unsuitable for virus culture attempts even though it did have brain lesions compatible with viral encephalitis.

Six horses that died in the Chesapeake and Suffolk area in the last two weeks with central nervous system symptoms were referred to the state Regional Animal Health Laboratory System for testing. (Scroll down for July 31 story.) At that time, veterinary officials recommended that horse owners vaccinate their animals every six to twelve months against the disease. This is particularly important in the Southeastern region of Virginia, where they recommended the six-month vaccination interval.

These cases of equine encephalitis followed a familiar pattern where the virus resides most of the year in wild bird or mammal hosts and only becomes a problem when there are enough mosquitoes present to transmit the virus from the reservoir into horses or people. Rainfall and temperature patterns this year have been favorable for the production of mosquitoes.

Typical symptoms of encephalitis include staggering, circling, depression, loss of appetite and sometimes fever and blindness. There is no cure for the disease, but there is an excellent vaccine, which is effective for 6 – 12 months. In an area where the disease occurs frequently, horses should be re-vaccinated every six months. Other prevention methods include destroying standing water breeding sites for mosquitoes, use of insect repellents such as DEET, and removing animals from mosquito infested areas during peak biting times, usually dusk to dawn