For years, scientists believed that mosquitoes were able to find us by zeroing in on the carbon dioxide in our breath. However, new research has shown that it is a combination of CO2, human odor and heat that lead the pesky insects to us.
A team of researchers led by Conor McMeniman at the Laboratory of Neurogenetics and Behavior, Rockefeller University, New York, were able to mutate a gene in the CO2 receptor in Aedes aegypti, a common type of mosquito which spreads yellow fever. The mutated insects were not able to detect or respond to CO2.
But they found humans to bite anyway. For mosquitoes, access to blood is crucial. It is only the female mosquitoes that bite, and the blood they collect is necessary to produce fertile eggs.
It turns out that when CO2 detection was taken away, the mosquito’s response to heat and odor cues where heightened. While attraction to live hosts was diminished, it didn’t stop them from finding people.
“Because blood feeding is such an important behavior for the mosquito, evolution has built in these mechanisms that ensure the most efficient use of the insect’s energy,” said McMeniman. “There are a lot of things that give off heat, and it would be a waste for a mosquito to try to bite all of them. But with several factors present, the insect can increase her chances of a fruitful bite in a cluttered sensory environment.”
The long-term goal of the research is to help design chemical repellents to block host-seeking behavior in mosquitoes that spread malaria.
Interestingly, loss of CO2 detection did make them less likely to find a mouse in the same test environment as the humans. The researchers concluded that without carbon dioxide as a cue, the effect of odor and heat are diminished as the insect moves farther away from the host.
The findings are recorded in a paper titled, "Multimodal Integration of Carbon Dioxide and Other Sensory Cues Drives Mosquito Attraction to Humans."
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