With the spike in the mosquito population coming this summer, and with four travel-related cases of the Zika virus in the county, the Alachua County Health Department has started trapping mosquitoes to gather data for the summer season.
Clarke Mosquito Control, a national county-contracted company, oversees the surveillance of mosquitoes and controls the mosquito population by putting larvicides, or bacteria that targets mosquito larvae, in the county-maintained basins. Alachua County does not spray for mosquitoes, but will allow larviciding when needed.
Clarke Mosquito Control collects data through the use of chickens, who are placed throughout the county where they are bit by mosquitoes and then tested for diseases. Chickens are used because they attract the mosquitoes that carry West Nile virus and Equine encephalosis virus. The chickens are unharmed because they have built up immunity against the diseases.
There also are 10 strategically placed Center for Disease Control light traps that run for 24 hours, attracting 33 different mosquito species. The company will issue weekly reports with the data until October.
The amount of each species that is found is reported to the Florida Department of Health, said Anthony Dennis, the environmental health director at the Alachua County Health Department.
During the first two weeks of data collection, two Aedes albopictus mosquitoes, known for carrying multiple viruses including yellow fever, dengue, chikungunya and Zika, were captured in the CDC light traps. The more aggressive Aedes mosquito, Aedes aegypti, has not been captured in Alachua County.
“I think that before the season is over we will have a locally transmitted disease in Florida,” said Casey Parker, a master's student at the UF Institute of Food and Agricultural Sciences Department of Entomology and Nematology, who has created a device geared specifically towards controlling the Aedes mosquito population.
This means by the end of September, it's likely that a mosquito from Florida will be infected with Zika and able to infect humans.
The number of A. albopictus is expected to go up as the rainy season continues. They are urban mosquitoes, meaning they are found near people, their preferred host, 80 percent of the time, Parker said. These mosquitoes looks for small amounts of standing water in which to lay their eggs, making many backyards perfect breeding grounds.
In general, mosquitoes don’t travel more than one-eighth of a mile once they find a place to lay their eggs. They stay where they have standing water and a blood-meal—humans, Dennis said.
A. albopictus are hard to control because of where they breed. They look for dark wet areas from gutters to flower pots. If adulticiding, or spraying to kill the mosquitoes, became necessary, it would have to be done
“Feet on the ground, in the backyards, backpack spraying; It’s the only way to get all those little crevices that could be breeding mosquitoes,” Dennis said.
The number of A. albopictus mosquitoes collected from CDC light traps doesn’t necessarily reflect the actual population in the area, as these mosquitoes aren’t particularly attracted to the lights. In addition, the surveillance of chickens doesn’t detect Zika because it’s a human virus. It focuses more on West Nile and other vector mosquito diseases, Dennis said.
A BG-Sentinel trap is more effective for collecting Aedes mosquitoes, Dennis said. The city of Gainesville is already using them and Dennis plans to start placing them on the ground near the CDC light traps.
The trap is an open-topped white cylinder with a fan at the bottom that releases a synthetic human smell out in the air. A cooler of dry ice is hung over the cylinder, which pulls in carbon monoxide. The combination of the human smell, used as bait, with the carbon monoxide acts as a lure for Aedes mosquitoes.
After the trap sits out for 24 hours, Dennis will collect the mosquitoes from the trap and send them to Peter Jiang, an entomologist with Gainesville Mosquitoes Control, who will determine the species.
With the data collected from the summer program, fliers with information on how to protect against mosquito bites and breeding will distributed through the county to schools to inform students and their parents about prevention methods.
The Alachua County Health Department's biggest defense against mosquitoes this summer is people who are misinformed, Dennis said.
“For us, it’s surveillance and communication, communication, communication,” Dennis said.