Mild Winter Brings Early Onslaught of Mosquitoes: Have Equids Vaccinated Against Sleeping Sickness

After a mild winter, Louisiana already has reported its first case of Eastern Equine Encephalitis (EEE), or "sleeping sickness" in a six-year-old unvaccinated Shetland pony in Vernon Parish, adjacent to Texas' Newton County. "We recommend that owners have their equine vaccinated against this mosquito-borne disease, if they live east of Interstate 35, or if they plan to travel to the area with their animals," said Dr. Terry Beals, Texas' state veterinarian and executive director of the Texas Animal Health Commission (TAHC), the state's livestock health regulatory agency.

"Veterinarians in Texas should report any cases to the TAHC or to the Texas Department of Health, so the incidence of the disease can be tracked."

Dr. Joe Garrett, a veterinary epidemiologist with the Zoonosis Control Division of the Texas Department of Health, said encephalitis cases in equine signal public health authorities that infected mosquitoes are or have been in the vicinity. Although no cases have been reported in Texas in 20 years, humans also can contract the virus from infected mosquitoes. He advised that ordinary precautions be taken, such as controlling pests and wearing mosquito repellent. Symptoms of the infection in humans include fever, headache, vomiting, lethargy, neck stiffness, convulsions and coma.

Equids affected by "sleeping sickness" or encephalitis develop central nervous system disorders, such as an irregular gait and circling, grinding of the teeth, drowsiness, and an inability to swallow. Affected animals may have paralysis of the limbs and be unable to rise. The TAHC and public health officials advise owners to have symptomatic animals tested, because the signs for rabies and "sleeping sickness" often mimic each other, and appropriate preventive measures must be taken, if an owner is exposed to rabies. In addition to horses, donkeys and mules, many species of birds, such as emus, ostriches and rheas also are susceptible to the "sleeping sickness" virus.

Dr. Beals said private veterinary practitioners can administer a vaccine to equine that will provide protection against the Eastern and Western strains of equine encephalitis. A "three-way" vaccine also will protect against the Venezuelan strain (VEE), which is considered to be a foreign animal disease and is recommended for equine residing or traveling in South Texas. In l996, several cases of VEE were diagnosed in Southwestern Mexico, and a widespread vaccination campaign curbed the outbreak. The VEE vaccine will cause a "false-positive" test result, so it should not be used on animals that must be tested prior to international travel.

To protect animals and humans from mosquitoes, Garrett suggested keeping window screens in good condition and urged outdoor enthusiasts to wear mosquito repellent. Outdoor containers, such as flower pots and rain gutters, should be drained to prevent a "breeding ground" for mosquitoes he said, and water in birdbaths should be changed frequently.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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