Eastern Equine Encephalitis (EEE) is a viral disease that affects the central nervous system of several different species of animals, but more often than not, it is most detected in birds and horses. After feeding on EEE infected birds, mosquitoes can transmit the disease to horses and sometimes humans. It is crucial to understand that EEE is transmitted through the mosquito/bird cycle and not a virus directly transmitted from an infected horse to other horses or humans, according to the Florida Department of Agriculture and Consumer Services. EEE is a huge concern especially for the Florida horse community. There has been over 70 reported cases of EEE annually in Florida, and, when conditions are favorable for the spread, that number can go up past 200 cases, leaving 90 percent of the affected horses dying. Signs of EEE in horses is varied with each individual animal, but the virus usually begins with “fever, depression and listlessness, which then progresses to more serious neurologic signs such as in-coordination, stumbling, circling, head pressing, coma and usually death,” according to the Florida Department of Agriculture. The virus attacks the brain and spinal cord and can also cause paralysis and muscle twitching, according to Vetlearn.com. Once a horse is infected and develops the neurologic signs of EEE, the disease is extremely fatal in 90 percent of cases. There have been two cases of EEE in horses in Madison County just this month, according to Dr. Lewis of Madison Veterinary Clinic, LLC.
The Florida Department of Health has also confirmed a case of EEE in a horse in Jefferson County this month. Florida Department of Agriculture reports that EEE occurs in hot, rainy weather. This climate is perfect for the expansion of mosquito populations, and outbreaks are expected from mid-summer to August in both humans and horses. August is especially considered the peak month for EEE. However, the risk of exposure of EEE varies from year-to-year, and the risk of infection exists wherever mosquitoes may be in the U.S. EEE is found more in the eastern parts of the United States. There is a vaccine to reduce the risk in EEE in horses. The American Association of Equine Practitioners considers the vaccination for EEE a “core” vaccination, meaning it is crucial for a horse's health. In adult horses, two vaccinations four to six months apart should be followed by a yearly booster. More frequent vaccination may be needed for places like Florida that have mosquitoes year round. The EEE vaccine has been out for 50 years, according to Lewis. Horses are to go through the standard procedure of vaccinations twice a year, one in the spring around February and March, and another in the late summer in August or September. “If the horses are vaccinated, they don't get [Eastern Equine Encephalitis],” said Lewis. “If they don't, then they have a pretty high risk of getting the virus.” The vaccination is “very effective” and, if given at the standard procedure, will prevent many horses from getting EEE. Owners of horses are encouraged to stable their animals during peak mosquito feeding times at dusk and dawn. Insect screening and fans may also reduce a mosquito's access to a host. The Department of Agriculture also encourages horse owners to purchase repellents containing DEET.
While there is no vaccine for EEE in humans, the Center for Disease Control and Prevention (CDC) has several recommended approaches for reducing risk, such as wearing repellent, long-sleeves and pants, having secure screens and doors to keep mosquitoes out and ridding of any stagnant water around. Water buckets, troughs, wading pools, bird baths, wheelbarrows or any other containers that hold water should be cleaned or emptied on a weekly basis. Signs of EEE in humans, according to the CDC, include a sudden onset of headache, high fever, chills and vomiting that may progress into disorientation, seizures or coma. EEE is one of the most severe mosquito-transmitted diseases in the U.S., leaving 33 percent mortality and significant brain damage in most survivors. Contact your veterinarian if you see any potential signs of Eastern Equine Encephalitis in livestock, and be sure to consult with your healthcare provider if you think you or someone you know has EEE. Reading this article could save the lives of those who walk on two legs or four!