A horse in the town of Morristown has died of Eastern equine encephalitis, a virus carried by mosquitoes, St. Lawrence County Public Health Director Susan J. Hathaway said.
The horse is the first EEE case found in New York State this year.
There have been three human deaths over the last three years in Central New York, including a child in Oswego County last year, due to the EEE virus. The virus rarely is transmitted to people but can cause serious illness or death.
Last year, EEE was also responsible for the death of a horse in St. Lawrence County.
People who are infected may have a range of symptoms, from a mild, flu-like illness to more serious complications such as seizures and coma.
People should protect themselves when outdoors by using insect repellent containing DEET, picaridin or oil of lemon eucalyptus, and by wearing long pants and long sleeves.
Free treatments to rid areas of standing water such as pools or ornamental ponds are available from the county Soil & Water Conservation District, which is open from 8 a.m. to 4:30 p.m. Monday through Friday at 1942 Old DeKalb Road in Canton.
The county started off with 19 cases of the larvicide and has five left, Manager Dawn C. Howard said.