Increase in mosquito-borne disease keeps equine industry vigilant

By Peter Kent

At a measly 3 milligrams, the common mosquito seems an unlikely match for a thousand-pound horse.

But each year, mosquitos bearing deadly viruses infect dozens of horses in South Carolina, claiming equine lives and threatening humans as well.

Boyd Parr, South Carolina State Veterinarian and director of Clemson’s Livestock-Poultry Health unit, leads the fight against such threats as Eastern Equine Encephalitis (EEE) and the West Nile virus – two diseases that can affect humans as well as horses.

According to Parr’s official count, a wet year and burgeoning mosquito population brought 49 cases of EEE in 2013 – more than three times the number a year before – and three cases of West Nile. Nearly half the counties in the state reported infections.

“These numbers are a vivid reminder of the threat that mosquito-borne diseases represent to horses in our state.” he said. “Maintaining protection by vaccinating horses is important every year.”

Parr urges horse owners to consult with their veterinarians to be sure vaccinations against both EEE and West Nile are up-to-date – an important p[recaution in a state with more than 80,000 horses valued at more than a third of a million dollars.

The EEE virus is maintained in nature through a cycle involving the freshwater swamp mosquito Culiseta melanura, commonly known as the blacktailed mosquito. Two to three days after becoming infected with EEE virus, a mosquito becomes capable of transmitting the virus. Infected mosquitoes that feed on both birds and mammals can transmit the disease to horses and humans.

Any livestock (including horses) that display neurologic signs – stumbling, circling, head pressing, depression or apprehension – must be reported to the state veterinarian at 803-788-2260 within 48 hours, according to the state law.

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