Florida Owners Encouraged to Vaccinate Horses against EEE

Florida Owners Encouraged to Vaccinate Horses against EEE

Vaccinating horses against EEE coupled with mosquito control are the most important ways to minimize an animal's chances of becoming infected.

Photo: Anne M. Eberhardt/The Horse

The Escambia County, Florida, Mosquito Control Division is encouraging horse owners to take preventive actions by vaccinating their horses against Eastern equine encephalitis (EEE) in the light of increased production of mosquito species that could carry and transmit this widespread disease.

Recent local weather events have contributed to the emergence of both the primary and secondary vectors of EEE, a severe to fatal disease transmitted to horses by several distinctive mosquito species. Horses are “accidental hosts” of this disease, with a natural cycle that typically involves birds and the primary vector, Culiseta melanura, inhabiting cypress hammocks and other freshwater swampy areas.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures.

The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care; fatality rates reach 75-80% among horses. Horses that survive might have long-lasting impairments and neurologic problems.

Vaccinating horses against EEE coupled with mosquito control are the most important ways to minimize an animal's chances of becoming infected. In the northern regions of the United States, most veterinarians recommend vaccinating horses in the spring prior to peak mosquito levels. In the south, where mosquito populations are present year-round, veterinarians might recommend more frequent vaccination.

Minimizing mosquito populations near your horses by eliminating mosquito breeding and resting areas will reduce the chances these insects bite and infect horses and the people who care for them. For example, reduce or eliminate sources of stagnant or standing water, remove muck from areas near the horses, stable horses during peak mosquito periods (i.e., dawn and dusk), use equine-approved mosquito repellants, place fans inside barns or stalls to maintain air movement, keep weeds and grass trimmed, and avoid using incandescent bulbs inside stables at night. Instead, place incandescent bulbs away from the stables to attract mosquitoes to areas away from horses.

Humans can take actions on their own to prevent their exposure to mosquitoes by avoiding activity at the times of dawn and at dusk when mosquitoes are active, dressing to cover exposed skin, using a mosquito repellent that contains DEET and by draining large and small water-filled containers, as may breed nuisance pests.

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