Horse Owners Beware: Eee Has Been Found in Massachusetts’ Mosquitoes

Author: Mosquito Squad of Chelmsford & Cambridge

Deadly for humans and horses, Eastern Equine Encephalitis (EEE) has been found in mosquitoes in Massachusetts for the first time this year. EEE “Triple E” is a rare virus carried by mosquitoes and transmitted to humans and horses. It is normal to see some EEE activity within the mosquito population starting around mid-July each year. The first EEE-positive mosquito in Massachusetts in 2016 came from a sample in Middleborough, but there have been no human or horse cases this year.

The Trouble with Triple Eee

While EEE is extremely dangerous to humans with a 33% mortality rate, it is not as common for humans to become infected. The type of mosquitoes known to carry EEE prefers swampy wetlands where people don’t normally spend a lot of time. Horses and other equine are at a higher risk and typically there will be few EEE cases in horses each year before any human cases occur. While there is a vaccine available for horses, EEE has a 75-100% mortality rate.

Symptoms of Eee in Horses

According to the University of Connecticut, horses with EEE can experience non-specific symptoms that can include fever, poor appetite, and stiffness. When EEE progresses, and it most often will, an incubation period of 1-3 weeks will pass. The symptoms that follow incubation can include propulsive walking, depression, and drowsiness, aggression and excitability. Some may become frenzied after stimulation, and later symptoms can include head pressing, blindness, circling, head tilt, and limb or facial trembling or twitching which is a sign of severe brain dysfunction. Death can occur as early as 2-4 days after these severe symptoms appear. Call your veterinarian immediately if you suspect EEE in your horse. Supportive care is the only treatment, and those who survive may experience permanent damage.

Follow your veterinarian’s advice for how often your horse should receive the EEE vaccine for the best protection, especially now that EEE has been found in Massachusetts’ mosquito population. Follow to view daily updates on mosquito testing in Massachusetts. With EEE and West Nile Virus in the area, it is good to know how close it has been found to home.