Eastern equine encephalitis (EEE) case reports have risen into the hundreds already this year, with confirmation of equine cases in at least nine states. Florida has been hit hardest, with a total of 183 equine cases reported from 47 counties as of July 31. The EEE mortality rate is up to 90% in some areas, and veterinarians continue to advise horse owners to vaccinate their animals against the disease.

Bumper mosquito crops, warmer temperatures, and rains producing mosquito breeding havens have been implicated in the high number of cases, which began appearing in April. However, veterinarians in the Southeast have said that the disease is cyclic and that they were due a difficult EEE year.

Other states experiencing EEE include Alabama, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, and Virginia. (See comparisons of equine case totals in 2002 and 2003 in the accompanying chart.) EEE has been found in birds in Indiana and West Virginia.

Venaye P. Reece, DVM, equine programs coordinator and state animal emergency response coordinator with South Carolina’s state veterinarian’s office, said her state’s “case numbers are up near 80, and climbing, and in 23 counties so far. Numbers are increasing almost daily.” She added that most of the cases are in non-vaccinated or not recently vaccinated horses