We’re all familiar with the annoying summertime feeling of mosquitos constantly buzzing around us, looking for a bite to eat. Even worse, many mosquitoes can carry deadly infectious diseases, such as the Zika virus or malaria. The latter, in particular, poses significant health threats around the world, with about half of the world’s population living in areas known to have high rates of malaria transmission. In fact, the CDC estimates that 627,000 people die every year from malaria. To make matters worse, many of these mosquito species seem to have developed an evolutionary exclusivity for humans.
But how exactly do mosquitoes know how to seek out humans and target us with such precision? A new research study published in Nature may have some answers.
Researchers at Princeton University suspected that for a species to thrive so well, despite being dependent on a single species for eating, there must be a complex mechanism at work to help mosquitoes find their only prey. To test these mechanisms, researchers focused specifically on how mosquitoes detect smell and how they distinguish between human smells and those of other species, paying particular attention to the connection between brain activity captured through imaging technology and the signals mosquitoes pick up on to detect human smells. Basically, what do mosquitoes smell, and how do they smell it?
Imaging mosquito brains was no easy feat. The mosquitoes had to be genetically engineered so that their brains would light up. Then, while inside the research team’s novel imaging tool, researchers would present mosquitos with both human and non-human animal smells. But because the compounds forming human odors and the odors of other animals overlap in significant ways, researchers looked for compounds that were more pronounced in human odors. They identified decanal and undecanal as more prevalent in human odors, and developed odors that were very obviously human.
Surprisingly, however, mosquitoes actually used a fairly simple way to identify human odor over other types of mammal odors. Basically, the mosquitoes had two areas of their brain active when being presented with the different types of odors. One was active in a range of smells, while the other was active only for human smells. Researchers postulate that this either-or cognition, though simple, is how mosquitoes can target humans with such a degree of accuracy.