The Massachusetts Department of Public Health (MDPH) last week confirmed two additional cases of Eastern equine encephalitis (EEE) in horses, according to press releases from the agency.

On Sept. 6, the MDPH announced that a horse residing in Belchertown had tested positive for the mosquito-borne virus. On Sept. 7, the agency announced that a horse stabled in New York state had contracted the virus, and it is believed the horse was exposed while recently in the Massachusetts town of Halifax.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Its fatality rate in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures. Sixty equine EEE cases were confirmed in the United States in 2011, according to USDA Animal and Plant Health Inspection Service equine disease surveillance. Last year Massachusetts confirmed one EEE case in a horse in Worcester County.

In late August, Massachusetts’ first equine EEE case was identified in a Georgetown horse