EEE in New Jersey horses

A 12-year-old Camden County, New Jersey, gelding has tested positive for Eastern equine encephalitis (EEE). This is the second reported case of EEE in New Jersey horses in 2018.

The horse had not been vaccinated against EEE and was euthanized on Aug. 27.

“With this being our second case of Eastern equine encephalitis reported in the last two weeks, we are reminding horse owners of the high importance of having their animals vaccinated against diseases spread by mosquitoes,” said New Jersey Secretary of Agriculture Douglas H. Fisher. “Vaccinated animals are much less likely to contract deadly diseases such as EEE and West Nile Virus.”

The first case of EEE in New Jersey horses in 2018 was confirmed in a Monmouth County mare last week.

In 2017, officials confirmed six cases of EEE in New Jersey horses.

EEE 101

A viral disease, EEE affects the central nervous system and is transmitted to equids by infected mosquitoes. Clinical signs in horses 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; and
  • Severe central nervous system signs, such as head-pressing, circling, blindness, and seizures.

The disease can progress rapidly, with death occurring two to three days after onset of clinical signs despite intensive care in some cases. Fatality rates can reach 75-80%. Equids that survive might have long-lasting impairments and neurologic problems.

Studies have shown that vaccines can be effective EEE prevention tools. Horses vaccinated in past years need an annual booster shot, but veterinarians might recommend two boosters annually—one in the spring and another in the fall—in areas with prolonged mosquito seasons. In contrast, previously unvaccinated horses require a two-shot vaccination series in a three- to six-week period. Full immunity takes several weeks to achieve.

In addition to vaccinations, owners should work to reduce the mosquito populations and possible breeding areas and horses’ exposure by:

  • Removing stagnant water sources;
  • Dumping, cleaning, and refilling water buckets and troughs regularly;
  • Keeping animals inside during the bugs’ feeding times (typically early in the morning and evening); and
  • Applying mosquito repellents approved for equine use.