By RAY WYCHE

The first case of Eastern equine encephalitis (EEE) reported in North Carolinas this year has led to the death of a horse in the Riegelwood area.

The state Department of Health and Human Services confirmed after tests that the horse had the disease, caused by the bite of an infected mosquito, and had to be euthanized. The mortality rate for equines (horses, mules and donkeys) that contact EEE runs from 75 to 90 percent. The small number of animals that survive EEE usually suffer permanent neurological damages and are normally put down.

The horse had not been vaccinated with a serum that would have immunized it from EEE, according to Debbie Crain of the N.C. Department of Health.

EEE is one of three viral diseases caused by bites of infected mosquitoes. The virus attacks the brain and spinal cords of the animals and early symptoms include fever, depression and muscle weakness. As the sickness progresses, head pressing, compulsive circling and blindness become evident, and in the last stages, the animal goes into convulsions.

There is no treatment for the disease.

Mosquito-borne viral diseases usually appear in the summer months when people are outdoors and mosquitoes are numerous and active. In the state thus far this year, a young girl in Buncombe County in the western part of the state has been infected with LaSalle encephalitis, the most benign of the three viral diseases caused by mosquito bites.

EEE can attack humans and can cause about a 50 percent mortality rate, mostly among the elderly and young people who have become infected. West Nile virus is the second most common mosquito-borne illness in the state, the state Department of Health says. EEE, while rarely occurring, is the most deadly of the three.

Brandon Grigsby, environmental health specialist with the Columbus County Health Department, said that the worst period of the year for mosquito bites is now beginning, and that people should take precautions.

“Fall is the worst time,” Grigsby said. “August and September are the worst months.”

In the county thus far this summer, Grigsby said calls about problems with large populations of mosquitoes have not been excessive. When the local health department receives a large number of complaints about mosquitoes in a certain area, health department technicians conduct a “landing count,” counting the number of mosquitoes observed landing on bare flesh within a specified period. If the landing count is high enough, a truck spraying insecticide is dispatched to the area.

Grigsby said reports from the state health department have recorded two cases of west Nile virus in Craven and Beaufort counties, and a case of EEE virus in a sentinel flock of chickens in Carteret County.

Groups of chickens are kept in several eastern North Carolina counties and blood samples from the flocks are periodically examined by state health department technicians for the presence of any mosquito-borne viruses.

A sentinel flock at the Whiteville Wastewater Treatment Plant near White Marsh east of Whiteville has not shown any positive results from tests thus far this summer, Grigsby said.

State health officials said 16 cases of EEE virus were found last year in the state, while five were reported in 2004.

Grigsby and state health officials are continually warning people to help reduce problems caused by mosquitoes by emptying outside containers of water that offer breeding places for the pests, and to apply insect repellants before going outdoors.

People should avoid outside activities in the early morning and late afternoon hours, if possible, when mosquitoes are likely to be more active.