Many people suffer from constant mosquito bites, while others don't notice any bites at all. This mystery has long puzzled scientists.
Previous research has suggested that human body odor may be the reason for its attraction to mosquitoes, but most previous studies examined only one type of mosquito at a time, making it unclear whether different types of mosquitoes prefer different human odors.
In a new study published in the scientific journal iScience, researchers decided to unravel this mystery through an experiment involving about 120 volunteers in Miami, Florida, USA.
The study found that skin bacteria and body odor are the two main factors behind why some people are frequently bitten by mosquitoes, while others are completely ignored.
During the study, researchers asked each volunteer to place their arm inside a special odor-analysis chamber called a "uniport olfactometer" to measure the odor emitted. At the other end of the tube, they placed three different types of mosquitoes: Aedes aegypti (the vector of dengue fever), Aedes albopictus (the Asian tiger mosquito), and Aedes albopictus (the southern house mosquito).
Because the five-striped mosquito bites at night, researchers had volunteers wear nylon sleeves covering their arms during the night hours, in order to absorb and trap the scent of the skin for later analysis.
The scientists also took air samples from the area surrounding each participant's arm and analyzed the chemical composition of their skin odors. In addition, the participants' forearms were swabbed and DNA was sequenced to identify the types of bacteria living on their skin.
The researchers then compared the most and least attractive volunteers for each of the three mosquito species.
The results were interesting, as the team found that the Aedes aegypti mosquito showed a slight preference for male participants, while the other two species showed no gender bias between males and females.
In contrast, the Aedes albopictus mosquito was attracted to people who carried specific scents such as ketone compounds.
The researchers explained that skin bacteria feed on sweat and natural oils secreted by the body, converting them into specific odors that mosquitoes can easily detect. Overall, the scientists found 246 different types of skin microbes among the participants, including Corynebacterium kefirresidentii, Cutibacterium granulosum, and a variant of Staphylococcus epidermidis.
The researchers wrote in their study, "Each mosquito species exhibited distinct responses to human individuals, confirming the existence of unique and shared signals for targeting their hosts." They added that "uncovering this complexity will aid ongoing efforts to develop microbial-based mosquito repellents that produce repellent compounds or reduce attractant signals."
These findings open the door to developing new and innovative methods of mosquito control, based on modifying skin bacteria or producing natural compounds that repel insects, instead of relying on traditional chemicals.
