Mosquitoes in Cuyahoga County are testing positive for West Nile virus – a fact known because of a dedicated public health effort to kill, trap and track the biting bugs.
As of late July, four of 44 mosquito samples the Cuyahoga County Board of Health submitted to the state this summer tested positive for West Nile. One sample can include approximately 20 to 30 mosquitos.
“Historically, we see more infected mosquitos in late July and August, so this activity is normal,” the county board of health wrote about the results.
West Nile virus can cause fever and flu-like symptoms and, in the worst cases, swelling in the nervous system, according to the Cleveland Clinic. Mosquitoes can spread the virus to humans by biting them. The county health board has not reported any human cases of West Nile virus this summer.
The county is warning residents to be extra vigilant about wearing bug spray and avoiding the outdoors during peak mosquito hours – around sunrise and sunset.
The county health board tracks viruses such as West Nile through its mosquito control program: an effort that includes both killing mosquito larvae and trapping and testing the adults for diseases that can be spread to humans. So far this summer, the program has trapped about 1,900 mosquitoes. About 80% of those have been tested.
“You’re never going to get them all,” said Mason Leuthaeuser, a registered environmental health specialist who oversees the mosquito control program. “But we can try our best to knock down all our problem sources.”
The mosquito control program was born 50 years ago in response to a local outbreak of mosquito-borne encephalitis, according to the board’s website. Encephalitis is a dangerous virus that inflames the brain and spinal cord. In 1975, hundreds of people across Ohio contracted it.
Since then, Ohio has experienced several outbreaks of West Nile virus cases, including in 2002 and 2012, Ideastream reported.
The mosquito control program costs just about $47,000 a year to run, funded by the county health board’s general fund. The Ohio Department of Health sometimes gives out grants, too – and it’s the state that actually tests the mosquitoes for diseases. Historically, the state only tested mosquitoes for West Nile virus. But this year, it expanded the program to test for a variety of other diseases, including Eastern equine encephalitis and La Crosse virus.
In addition to Leuthaeuser, the program employs four summer workers – typically college students interested in public health. The team identifies standing bodies of water that can breed the bugs. In the springtime and early summer, the team treats the water with a substance that kills mosquito larvae before they hatch. Then, in the later summer, they focus on trapping adult mosquitoes to test whether they carry viruses.
The program used to spray neighborhoods with insecticides to kill adult mosquitoes, a process called “adulticide.” That’s not so common anymore because it’s the least effective way to kill the bugs, Leuthaeuser said. Plus, the chemical spray often scared people, even though it’s not harmful, he added.
The board of health provides mosquito control across all Cuyahoga County cities except Cleveland, which has its own public health department and mosquito prevention program. In addition to working with municipalities, the board of health responds to concerns from individual residents about high numbers of mosquitoes on their properties.
Mosquito complaints this year are already double last year’s. Leuthaeuser credits that to a particularly wet spring that had a few high-temperature days.