EEE Hitting Louisiana Horses

Eastern equine encephalitis (EEE) has caused the deaths of eight horses in Lafourche Parish, La. Veterinarians also suspect the virus in two additional cases of equine illness.

Louisiana Department of Agriculture and Forestry Commissioner Bob Odom released a statement Aug. 3 on the mosquito-borne virus' emergence in the state.

"Since there is no cure for Eastern equine encephalitis [only supportive care], I am urging horse owners to vaccinate their animals," Odom said. "This is a very preventable disease, but often horse owners wait until it's too late."


The progression of EEE is swift and ugly. Affected horses will struggle with muscle tremors, weakness, and staggering gaits, and they might circle aimlessly or tilt their heads at odd angles.

Horses that have not been vaccinated for EEE should have two doses of the vaccine given about two weeks apart. An annual booster protects horses that have been vaccinated.

Odom noted that veterinarians in Louisiana should report any suspected case of equine neurologic encephalitis.

Eastern equine encephalitis is of special interest to veterinarians and human health authorities, as the virus can also infect humans. The virus cannot pass directly from horses to humans (mosquitoes are required to transmit it to mammals from infected birds), but horses can act as sentinels to alert public health officials that the virus is present in the area. There is no vaccine for humans.

According to the Department of Agriculture and Forestry statement, clinical signs of EEE in horses include depression, ataxia, a sleepy appearance, circling, and recumbency. The virus causes swelling of the brain, and the mortality rate is around 90%.

"Only rarely do horses recover from Eastern equine encephalitis," Odom stated. "Even when an animal doesn't die, it is almost always brain-damaged and is never usable again."

According to the equine arbovirus reports compiled by the USDA's National Animal Health Surveillance System (NAHSS), a national reporting system for equine disease, there were there were 16 cases of EEE in Louisiana horses last year.

There are an average of five humans cases of EEE per year detected nationally, according to the Centers for Disease Control.

For more on EEE see

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care.

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