Florida officials have already tallied 51 confirmed cases of Eastern equine encephalitis (EEE) in 2005 as of June 17 (46 of them since May 1), and the state could be approaching a record year for EEE infections. Florida practitioners received a letter last week from Michael A. Short, DVM, veterinarian manager of equine programs in Florida’s Division of Animal Industry, urging them to submit samples from suspected cases.

The situation is reminiscent of the high-level years 1982 and 2003, in which reports topped 200 EEE cases. At least 20 of the 2005 cases have died or been euthanatized as a result of the infection. Central Florida has experienced the most cases so far, and most of the affected animals have not been current on their EEE vaccinations.

Eastern equine encephalitis is caused by a virus found in wild birds that is transmitted to horses and humans via the bite of an infected mosquito. Horses do not develop high enough levels of the EEE virus in their blood to be contagious to other animals or humans. Onset of clinical signs can be rapid and severe; signs can include fever and neurologic signs such as ataxia (incoordination), head pressing, or muscle fasciculations (twitching).

“Most of the animals that contract EEE die,” said Short. “The majority of EEE cases that we follow up on have either been euthanized or died from the disease. I believe the literature usually states the EEE is fatal in approximately 90% of cases and this is accurate in my own experience