Your backyard can be more than a place to garden, play with your dog, spend time with the family or relax. It can also be a place where people encounter mosquitoes capable of transmitting dengue, according to a University of Florida study.

With the rise of dengue cases in Florida this year, UF researchers at the Institute of Food and Agricultural Sciences (UF/IFAS) Florida Medical Entomology Laboratory (FMEL) are urging residents to take precautions, especially in the unprotected recreation spaces outside of their walls.

Researchers at UF were surprised to find that Aedes aegypti, the primary mosquito responsible for dengue, was relatively common in residential yards in Indian River County, where they expected to find more of a secondary dengue-transmitting mosquito known as Aedes albopictus.

“It was definitely surprising to find that we saw more Aedes aegypti,” said co-author Panpim Thongsripong, an assistant professor of vector-borne disease ecology at FMEL. “We expected to find more Aedes albopictus in suburban Indian River County because of the area’s vegetation and residential setting.”

The finding emerged from the study, “How often, when, and where do people get bitten by mosquitoes? Characterizing human–mosquito contact using Bite Diary,” which examined where and when people are bitten by mosquitoes, information that mosquito surveillance does not always capture.

Bite Diary, a temporary smartphone-based app developed by researchers at FMEL in Vero Beach, allowed people to report when and where participants were bitten by mosquitoes. Simultaneously, researchers were trapping mosquitoes in their residential yards to compare results. The researchers also worked closely with the Indian River Mosquito District in non–residential public areas where traps had been placed.

Eighty-three people participated in the study, with 71 registering for the Bite Diary smartphone app. Participants recorded mosquito bites and their outdoor activities over a four-day period. Researchers also trapped mosquitoes in 78 residential yards, collecting 3,788 female mosquitoes representing several species, including vectors that can potentially transmit mosquito-borne diseases.

The study’s bite records show that exposure often happened during ordinary activities close to home. Dog walking and gardening were among the activities frequently reported when participants recorded mosquito bites. Much of the exposure occurred around participants’ homes.

“This could help public health officials think differently about mosquito prevention. While many mosquito control and public health agencies already encourage personal protection and public awareness, our findings provide additional evidence supporting those efforts,” said Cynthia Lord, associate professor of population modeling at FMEL. “Public information campaigns about use of personal protection, activities that increase mosquito contact and awareness of the time of day may be beneficial.”

The study found that the number of mosquitoes collected in a yard did not correlate with the number of bites people reported. Instead, people who spent more time outdoors during evening hours were more likely to report being bitten.

“A lot of the time, we put mosquito traps in a park or an empty lot,” said Thongsripong. “But mosquitoes like Aedes aegypti really love to breed in containers around people’s homes.”

The findings do not mean dengue is circulating in Indian River County. But this underscores why researchers say residential yards can be important places to monitor mosquitoes and understand where people may encounter species capable of transmitting disease.

"People who spend more time outdoors during dawn and dusk, when mosquitoes are more active are at higher risk and should consider using bite protection tools such as repellents containing active ingredients like DEET, picaridin and PMD,” said Thongsripong.

The findings highlight several simple measures that can help lower the risk of mosquito bites and reduce mosquito populations around homes.

“Minimizing water-holding containers or dumping them frequently can reduce populations of key mosquito species such as Aedes aegypti and Aedes albopictus, likely reducing bites on people in the yard,” said Lord. “These species can lay eggs and develop in very small amounts of water.”

Another takeaway from the study demonstrates how technology can help researchers capture information that traditional mosquito surveillance cannot, said Thongsripong.

Incorporating information about human behavior alongside mosquito surveillance could provide a more complete picture of mosquito exposure and ultimately help improve how mosquito-borne disease risk is understood.

The study was funded by a UF/IFAS Faculty Seed Grant of $85,000 from the Innovation Hub for Urban Pest Management in the UF/IFAS Department of Entomology and Nematology.