SATURDAY, SEPTEMBER 24, 2016

Researchers learn how mosquitoes detect humans

Ring Cardé, a professor of entomology, conducted the latest mosquito study. | Courtesy of eurekalert.org

Researchers at the University of California at Riverside recently determined that indoor, malaria-carrying mosquitoes can detect a human’s presence by changes in carbon dioxide levels, instinctually telling the insect to begin feeding.

Researchers plan to use this information in the fight against malaria.

One of the most common malaria-spreading mosquitoes is a female from the Anopheles gambiae species. This mosquito spends the majority of its life inside. The release of carbon dioxide greatly increases the chances of the mosquito choosing to land on a human’s skin. Even the slightest increase in carbon dioxide attracted the mosquitoes.

The misquotes displayed what the researchers called a “sit-and-wait” strategy, in which the mosquitoes would endure the scent of humans in an empty house until the living human arrived in person. This conserves the mosquito’s energy until it can feed.

Researchers wanted to see whether skin odor influenced the mosquitoes’ feeding tendencies. To determine this, the team collected mosquitoes from Cameroon. To collect skin odor, they affixed white polyester gauze onto a subject’s skin for four to six hours. They used a night-vision video camera to record the mosquitoes’ activities.

Indoor mosquitoes are surrounded by human smells from clothing, bedding and other items, but the female Anopheles gambiae has only a weak response to the odors naturally released by human skin.

"Responding strongly to human skin odor alone once inside a dwelling where human odor is ubiquitous is a highly inefficient means for the mosquito of locating a feeding site," Ring Cardé, a professor of entomology, whose lab conducted the research, said. "We already know that mosquitoes will readily fly upwind toward human skin odor but landing, the final stage of host location, which typically takes place indoors, does not occur unless a fluctuating concentration of carbon dioxide indicates that a human host is present. It may be that upwind flight toward human odor has more to do with locating a human dwelling, which emits human odor even when its occupants are absent, than locating a feeding site per se."

Researchers plan to use this information to create new innovations for mosquito control.

Scientists plan to continue their research in other, related areas, such as the exact extent to which the skin odor affects the mosquitoes and whether carbon dioxide levels trigger the mosquito’s responses just as strongly in outdoor environments.