This 2006 file photo provided by the Centers for Disease Control and Prevention shows a female Aedes aegypti mosquito in the process of acquiring a blood meal from a human host. A study published Tuesday, Oct. 18, 2022, in the journal Cell, found that certain people really are “mosquito magnets” who get bitten more than others — and it probably has to do with the way they smell. Centers for Disease Control and Prevention via AP

James Gathany

The Mercer County Conservation District will return to Franklin Township and the surrounding areas this week or next to learn more about the number and types of mosquitoes infected with West Nile virus.

The conservation district detected the virus in mosquitoes collected from the township last week. There have been no reported cases in humans in the Butler County.

Officials from the conservation district will continue setting traps this week around the county, according to spokeswoman Megan Miller.

Businesses and residents in Franklin Township and the surrounding areas should take extra precautions against mosquito bites by using insect repellent, wearing long sleeves, checking that window and door screens are secure, and eliminating stagnant water, which creates mosquito breeding grounds, a news release from the conservation district said.

The disease is spread to humans by mosquitoes and presents nonspecific symptoms including fever; head and body aches; weakness; stiffness; numbness; and, in extreme cases, blindness, paralysis and vomiting.

“That is the hard part about it,” Miller said. “West Nile virus has nonspecific symptoms, so it can be hard to diagnose at first.”

Health care providers can test for specific West Nile virus antibodies to diagnose the disease, and it’s typically diagnosed by ruling out other diseases.

About 1 in 150 people infected will develop severe illness with symptoms lasting from a few days to several weeks, according to the Pennsylvania Department of Health. About 20% of infected patients will exhibit the minor symptoms, while 80% won’t exhibit any symptoms.

The department said people older than 60 or with health conditions — such as cancer, diabetes, high blood pressure, kidney disease and organ transplant recipients — are at greater risk of developing severe illness. About 1 in 10 people with severe illness affecting the central nervous system die.

Those who believe they are infected should seek immediate treatment, the conservation district said.

There is no vaccine or specific treatment for West Nile virus, the department said. Pain relievers can reduce fever and mitigate symptoms, but severe cases often require hospital treatment.

Gravid traps attract adult female mosquitoes. Submitted Photo

The conservation district, which covers testing for Butler, Mercer and Crawford counties, tests mosquitoes using gravid traps, Miller said. The traps look like a small toolbox with stagnant water in the bottom that traps mosquitoes while a battery-powered fan keeps them from escaping.

Residents can limit the mosquito population by removing standing water or receptacles that may accumulate standing water, drilling holes in the bottoms of containers to eliminate standing water and cleaning clogged gutters.

The Department of Health also recommends chlorinating swimming pools, removing discarded tires that can become larvae habitats and using bacillus thuringiensis israelensis, or bacillus sphaericus tablets to kill mosquito eggs in stagnant water.

The virus is spread to mosquitoes when they feed off infected birds or cattle, but only mosquitoes can spread it to humans. The virus is commonly reported each summer, and the risk will dissipate as the weather gets colder and mosquitoes die in late fall, the conservation district said.