Program Helps Local Officials Monitor West Nile Virus and Other Diseases in Hamilton County

The trap was waiting next to an abandoned house on Wilder Road for Drake Kovacs to return to recover his booty.

When the next morning's traffic was dispelled, Kovacs was back on the usual route through the Amnicola Highway. He turned the white Ford F-150 towards the tire shop and parked in front of the old house where, a month ago, his grip had been reported for a dangerous illness.

The location has everything Kovacs is looking for: stagnant water nearby, invasive scrub and tall grasses. This is the kind of place where, during the hot seasons, its target thrives. Old tires that contain pockets of water are favorite areas. It is also off the beaten track, so that a passerby is less likely to disturb the trap.

He caught a whiff of the spicy mixture – fermented hay, water and yeast – used to catch their catch while he was lifting the net filled with mosquitoes. It looked like a successful race. Because although most people do their best to avoid mosquitoes, Kovacs looks for them.

Mosquitoes are more than a nuisance. They carry life-threatening diseases, such as West Nile virus, that can affect humans and horses bitten by an infected mosquito.

There is no human treatment or vaccine against West Nile virus, and most healthy people do not notice when they are infected. However, some people develop fever and other symptoms, including headache, body aches, joint pain, vomiting, diarrhea or rash. In rare cases, infection with West Nile virus causes serious illness and can lead to death. The virus killed 167 people in the United States in 2018.

From 2012 to 2017, seven cases of West Nile Virus were reported to the Chattanooga-Hamilton County Health Department. It is also the most prevalent mosquito-borne disease in Hamilton County. That's why Kovacs' job as an environmental health technician in the health department is to trap the insects and send them to a state lab for them to be tested.

Kovacs uses what is known as a gravid mosquito trap designed to attract and catch female mosquitoes ready to lay their eggs. The smell of the fermented mixture draws them to the trap, where a fan sucks them into a net. There, they wait for the return of the Kovacs the next day and freeze them to death with dry ice.

He needs to preserve their fragile bodies to be able to look at them under the microscope and to spot the Culex mosquitoes – the yellowish brown mosquitoes with plain legs, without scratches. Culex is the carrier species of West Nile virus.

Using a tweezer, Kovacs selects each culex by hand, places up to 50 in a vial, indicating it with the address where the lot was trapped and shipped mosquitoes for them to be analyzed.

He repeats the operation from Monday to Thursday, from April 1 to September 30, as part of the mosquito surveillance program of the Ministry of Health.

The Chattanooga-Hamilton County Health Department launched its program last year as part of a statewide surveillance initiative. Grant from the Tennessee Department of Health to pay two trucks and eight traps, and the county pays the staff bill.

Last year, Kovacs and one of his colleagues also collected Aedes aegypti mosquitoes, which can transmit the Zika virus. The Zika virus is not yet established in the region but has become a major concern in 2015 and 2016 when epidemics in the Americas were linked to serious birth defects. Local transmission was limited to a few cases in Florida and Texas and no recent cases were reported in the United States. However, the virus remains a concern for travelers, especially pregnant women.

This year it's Culex and the West Nile Watch, which the health department also discovered last year in Hamilton County.

"The West Nile virus is the virus we see most often here, so it's the one we're worried about most," said Bonnie Deakins, director of environmental health sciences at the health department.

Kovacs took nearly four months to set traps all over the county, but he had the first sign that the virus was back in July. State laboratory results revealed that the mosquitoes trapped near the abandoned house were positive for the Flanders virus. The virus does not affect humans but indicates that West Nile virus is not far off.

"They told us to take it back, because apparently, if you find Flanders, normally you will find West Nile a few weeks later," said Kovacs. "That's exactly what happened."

West Nile also fell into a trap around the Amnicola road last year.

"It continues to appear for some reason," he said.

The most effective prevention against West Nile virus or any mosquito-borne disease begins "from the body to the outside," said Deakins.

Starting with the skin, use EPA approved insect repellents, wear pants and long sleeves, use mosquito nets on windows and doors and eliminate or reduce stagnant water – where mosquitoes breed – as far as possible.

"The Culex is what they call a container breeder." He likes small water containers, like plant-free plant pots, children's toys or even your gutters that can be stopped and restrained. of water, "she said. "If it's like a bird bath, you want to empty it once a week and rub it, then fill it again. Do not let the water stay there long enough for mosquitoes to come in." spend their entire life cycle. "

Meanwhile, the Kovacs will continue to hunt and trap mosquitoes until the end of their season in October. According to public health officials, most human cases of West Nile in the southeast occur in August and September.

People who think they are infected should consult a health care provider. More information on West Nile virus is available on the Ministry of Health website or by calling the Ministry of Health's Environmental Health Services Division at 423-209-8110.

Contact writer Elizabeth Fite at [email protected] or 423-757-6673.