Ashley Falat, an intern with the Henrico County Vector Surveillance and Control team (Photo courtesy Henrico County Vector Surveillance and Control)
It’s a mellow summer afternoon. The day is filled with radiant sunshine, a slight jasmine-scented breeze and, wait — is that the shrill of a mosquito?
Despite its small size, the dreaded insect can easily ruin summer reveries. They’ll stalk victims until they’re covered in itchy, irritating bites, some of which could transmit pathogens. It’s why Henrico County has assembled a team to protect residents.
Made up of medical entomologists and those with other scientific and stormwater management backgrounds, the Department of Public Works’ Vector Surveillance and Control group, also known as the Mosquito Team, spends April to about mid-November tracking, investigating and deterring these insects. Staff members also provide free mosquito inspections for county residents, and they give presentations to schools and other groups.
The Mosquito Team targets two of Henrico’s most prevalent species, (from left) the Asian tiger mosquito (Aedes albopictus) and the house mosquito (Culex pipiens). (Photo via iStock)
Though there are about 40 mosquito species in Henrico and about 55 in Virginia, there are two of primary concern: Asian tiger and house. The former is considered more of a nuisance, but the latter is known for transmitting West Nile virus, causing a disease that can induce fever, nausea and body aches in most cases and potentially death in severe infections. It’s a problem that tends to spike around August to the end of September.
Around 400 surveillance sites and 600 treatment sites are scattered across the county. These sections are determined based on population density and distance. “In more populous areas like the West End, we have monitoring sites potentially every few miles,” says medical entomologist Wes Robertson, who is a county environmental and vector management specialist. “In more rural areas such as the East End, it tends to be more spread out.”
But this all depends on numerous variables, as mosquito populations ebb and flow yearly. “A few years, numbers will be on the rise, and [some years] numbers peak out. [Other] years, they’ll crash and, after the crash, the numbers will rise back up,” Robertson says. It’s a wild ride affected by aspects such as drought and heat.
To thwart proliferation, the team relies on various methods, including spraying or hand-applying Bti, which is an eco-friendly granular larvicide made up of soil bacteria spores that naturally destroy mosquito larvae.
For adult mosquitoes, the team uses carbon dioxide and gravid traps. The first mimics a large organism breathing; it attracts mosquitoes who attempt to feed on it but find themselves instead captured by its strong vacuum suction. Gravid traps specifically target females. Featuring a mixture of heavily polluted and smelly water, the trap simulates a desired egg-laying spot. The adults are then collected and tested for pathogens.
Henrico’s mosquito squad formed in the early 2000s after the West Nile virus began spreading throughout the U.S., including in western Henrico. It was a way to help handle resident concerns and eventually grew into a comprehensive surveillance program. Today, the team consists of three full-time staff members with several seasonal workers, all on a mission to safeguard and educate locals about the insects.
The team’s success has led them to recently focus on other initiatives as well. In the past year, they’ve begun monitoring ticks for Lyme disease, as well as a pollinator program, something that could be key for fighting mosquitoes as some pollinators, like aquatic beetles, feed on them.
“Once biodiversity increases, we may have more natural control on pests,” Robertson says. “It’s another tool in the toolbox.”
This article has been updated since it was first published in the April 2024 issue.
