EEE: Massachusetts and Florida Feel the Sting of Mosquito-Borne Horse Disease

Yes, it’s that time of year. The mosquitoes are here. And with them come the fear, if not the reality, of diseases that could affect our horses or ourselves.

Here in Massachusetts, we’ve already had our first case of Eastern Equine Encephalities (EEE); a seven-month old Paso Fino colt was euthanized this week, as you’ll see in this video.

Florida averages over 70 reported cases of Eastern Equine Encephalitis in horses each year. In years when conditions favor the spread of the EEE, the number of reported cases can exceed 200, with over 90% of affected horses dying.

EEE is a viral disease that affects the central nervous system of many species of animals but is most often detected in birds and horses. The disease is transmitted to horses, and sometimes humans, by mosquitoes that have become infected after feeding on birds, which are circulating the virus. This is known as the mosquito/bird transmission cycle. It is important to remember that the virus is not transmitted directly from an infected horse to other horses or people.

Signs in infected horses can be varied but usually begin with fever, depression and listlessness, which then progress to more serious neurologic signs such as in-coordination, stumbling, circling, head pressing, coma and usually death. Once a horse becomes infected with the EEE virus and develops neurologic signs, the disease is fatal in roughly 90% of cases.

In most reported cases, the infected horses are four years or younger and are not current on vaccination against EEE. Older horses may be at risk as well. The initial series of two vaccinations should be given four weeks apart followed by semiannual boosters. In years with an above-average incidence of EEE, vaccination boosters given three times a year may be recommended. Ask your veterinarian at what age to begin and the frequency of foal vaccination, as it differs from adult horses.

All the literature I have (and that’s a lot), says that it is not enough to depend on a vaccination. It is still important to control mosquitoes and to prevent mosquitoes from biting your horse, even if your horse is vaccinated.

Center for Disease Control (CDC) map shows provisional veterinary cases of Eastern Equine Encephalitis in Florida in 2010. This is incentive to call a veterinarian for vaccination boosters!

In other disease-related news, a Quarter horse undergoing routine testing required for interstate transport tested positive for equine piroplasmosis in New Mexico last week, adding to worries about the resurgence in that disease, which affects transport of horses throughout the United States. Be sure that your horses’ health certificates are up to date if you are on the road this summer.

by Fran Jurga | The Jurga Report at Follow @FranJurga on for more horse health news!




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