Eastern equine encephalomyelitis (EEE) virus is quite active this year, and more than 120 cases have been reported in Florida. The state veterinarian’s office in Tallahassee, Fla. predicts levels equal to 2003 in which there were 200 cases of EEE in horses. 

During the 2003 outbreak, most of the infected horses were not vaccinated and were younger than three years of age. Horses that were vaccinated but became ill were also vaccinated less frequently overall. Some had only primary immunizations while others had primary immunizations and only yearly boosters. Vaccination against EEE should be performed at a minimum of two times per year and three times is recommended during years of high activity.

All horses that have not been previously vaccinated for EEE should receive two initial injections one month apart. Foals should be vaccinated at four, five, and six months of age if the mares have been vaccinated previously. If there is questionable immunity in the foals, vaccination can commence as early as two to three months.

Some EEE vaccines can be obtained over the counter. If any vaccine becomes warm while transported, it can be rendered inactive after only a short period; therefore, owners run the risk of inappropriate vaccination when performing their own immunizations