New mosquito research may help create better repellents

Scientists have been researching what attracts annoying mosquitos to humans. The team of researchers from Florida International University's (FIU) Laboratory of Tropical Genetics has identified the olfactory receptor that is used to detect odors in Aedes aegypti mosquitoes. This type of mosquito is known to transmit sometimes deadly diseases such as yellow fever and Zika.

The newly identified receptor is called Ionotropic Receptor 8a or IR8a. One of the researchers, biologist Matthew DeGennaro, says that science has known for 40 years that what attracted the insect was sweat and lactic acid. However, no one knew how the insect sensed those things.

Through a process of creating mutant mosquitos with missing genes, the team found that the IR8a mutant insects struggled to pick up the desired aroma of lactic acid and were unable to detect other acidic components of human odor. The insects could still detect CO2 and heat emitted by humans. However, the team says that the inability of the insects to smell the acidic volatiles in a human left half of the mosquitos uninspired to feed.

The researchers say that there are no redundant receptors in the mosquito that allows it to sense the acidic volatiles in sweat. DeGennaro says that blocking the IR8a pathway could be "an important" strategy for repellent design.

Removing the function of that receptor would eliminate about 50% of the host-seeking activity according to the scientists. He also notes that odors that mask the IR8a pathway could enhance the effectiveness of current repellents like DEET or picaridin. The team is currently looking at chemical screens that may disrupt the IR8a pathway.