GREENE TOWNSHIP, Mercer County — A rare mosquito-transmitted viral infection that can spread to humans has been found in northwestern Mercer County.
Officials from the Pennsylvania Department of Agriculture and the Department of Environmental Protection confirmed to The Meadville Tribune that eastern equine encephalitis has been found near Jamestown.
Eastern equine encephalitis (EEE) is one of a group of mosquito-transmitted viruses that can cause inflammation of the brain (encephalitis), according to the Centers for Disease Control.
Blood samples were taken Sept. 5 from a single horse in Mercer County’s Greene Township near Jamestown, Shannon Powers, press secretary for the Department of Agriculture, told the Tribune late Tuesday afternoon. Lab results from the Pennsylvania State Veterinary Lab confirmed the samples as containing the virus.
EEE is a virus carried by birds, but when mosquitoes bite an infected bird, the mosquitoes then can transmit the virus when they bite humans, horses and other birds. Disease transmission does not occur directly from person to person, according to the CDC.
EEE cases occur primarily from late spring through early fall. The last discovery of EEE in northwestern Pennsylvania was in September 2019 in Erie County. Spraying to prevent mosquitos potentially carrying EEE was done in northern Mercer County in September 2019 as well.
In the United States, an average of 11 human cases of EEE are reported annually, according to the CDC. However, EEE is considered one of the most serious mosquito-borne diseases in the U.S. due to its high fatality rate. About a third of patients who develop encephalitis due to EEE infection die, and many of those who survive have mild to severe brain damage, according to the CDC’s website.
Most people who become infected with EEE show either no symptoms or mild symptoms such as fever and joint or muscle pain, according to the CDC.
But severe cases of EEE infection include encephalitis, a swelling of the brain, or meningitis, a swelling of the membranes that surround the brain and spinal cord. The infection may begin with the sudden onset of fever, chills, headache and vomiting. The illness may then progress into disorientation, seizures and coma, according to the CDC.
It takes four to 10 days after the bite of an infected mosquito to develop symptoms of EEE, according to the CDC.
The Department of Environmental Protection has been monitoring for EEE periodically throughout the season in Crawford, Erie and Warren counties, said Tom Decker, spokesman for DEP’s s Northwest Regional Office in Meadville.
Mosquito traps were deployed in the Greene Township area of Mercer County and collected Tuesday, Decker said.
“Samples are being shipped to a DEP lab in Harrisburg for identification of the mosquitoes and possible testing if the main carriers of EEE are found,” Decker said in an email to the Tribune.
“The main carrier of EEE is Culiseta melanura, an uncommon mosquito that reproduces in acidic forested wetland environments,” Decker said. “DEP will continue to monitor the area until the mosquito season ends.”
The best way to reduce the chance of getting EEE is to prevent mosquito bites, according to the CDC as there is no approved vaccine for people or preventive drug.
Both state and federal officials recommend the following to reduce the risk to both humans and animals:
• Use mosquito repellant.
• Wear long sleeves and pants when weather permits.
• Stay inside at dusk and dawn when mosquitos are most active.
• Have secure, intact screens on windows and doors to keep mosquitoes out.
• Eliminate mosquito breeding sites by emptying standing water from flower pots, buckets, barrels, and other containers.
• Keep horse vaccinations up to date as there is an EEE vaccine for horses.
EEE symptoms in horses usually starts with a fever that may reach as high as 106 degrees for one to two days.
Additional symptoms may include: abnormal gait, aimless wandering, circling, difficulty breathing, drooping ears, drowsiness, head pressing, hyperactivity, inability to swallow, paralysis, restlessness, and sensitivity to sound.
Keith Gushard can be reached at (814) 724-6370 or by email at kgushard@meadvilletribune.com.
