A yearling Paso Fino filly in Hillsborough County, Florida, tested positive for Eastern equine encephalitis (EEE) on Aug. 10. The under-vaccinated filly showed signs of incoordination starting on July 21 and is currently still alive.
This marks the fourth confirmed case of EEE in Florida in 2026.
EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.
EEE 101
Eastern equine encephalomyelitis is caused by the Eastern equine encephalitis virus, with wild birds serving as the natural reservoir. Mosquitoes that feed on EEE-infected birds can transmit the virus to humans, horses, and other birds. Horses do not carry high enough virus levels in their blood to be contagious to other animals or humans. Due to the high mortality rate in horses and humans, EEE is considered one of the most serious mosquito-borne diseases in the United States.
Preventive tips for mosquito-borne diseases include:
- Avoid mosquito bites: Use insect repellent when outdoors, especially from dusk to dawn.
- Choose EPA-labeled products containing DEET, picaridin, or oil of lemon eucalyptus.
- Apply more repellent as needed, following label instructions, if mosquitoes are biting.
- Mosquito-proof your home: Install or repair window and door screens, and eliminate standing water where mosquitoes can breed.
- Protect your horses: Veterinarians recommend EEE vaccines for all U.S. horses, administered at least once a year. It’s not too late to vaccinate your horses this year.
- Use approved insect repellents to protect horses.
- If possible, keep horses indoors during peak mosquito times of dusk and dawn.
- Remove standing water, empty water containers, and clean water troughs weekly.
- Introduce mosquito-eating fish to water tanks or use mosquito dunks to control larvae.