Methods for controlling mosquitoes usually take two tacks: luring the mosquitoes into a trap away from humans, or discouraging them from biting at the source. Both methods can be expensive, unhealthy, cumbersome, or disgusting (the smell of rancid butter, anyone?) and generally aren’t scalable for the countries that suffer the most from mosquito-borne disease. New research explores how a mosquito’s neurons actually detect humans, and presents a promising class of chemicals, screened for safety, cost, and an appealing scent, some of which attract mosquitoes and others of which mask the smell of tasty human skin.
Previously, a lab at the University of California Riverside highlighted new chemicals that functioned similarly to DEET in inhibiting a mosquito's response to humans.
That same lab's new research expands the focus and the results by identifying the primary mosquito receptor involved in detecting carbon dioxide (from a human’s mouth or skin) and body odor. This receptor, referred to as cpA, binds with CO2 and chemicals in our B.O., but these receptors can be confused by other chemicals that fit into the receptor’s binding sites.
Modifying a computational method they had previously established for a fruit fly study, the team led by Dr. Anandasankar Ray was able to screen just under half a million potential chemicals for their potential to act as a binding chemical, or ligand, in cpA. The matches were then further screened for cost, human safety, and a pleasant smell.
With these 138 matches in hand, the researchers had a manageable pool of potential chemicals to test on mosquitoes. Through electrophysiological testing, where an electrode is placed in the mosquito's antenna, they directly measured how the mosquito receptors responded to a potential match.
Some of the matches increased the firing rate of the receptor as much as CO2 would, and thus could be a replacement for mosquito traps which rely on CO2 production (through things like dry ice or burning fuel). A minty-scented cyclopentanone was tested in a greenhouse setting, successfully luring the oblivious mosquitoes. To the team’s knowledge, no other chemical before has been able to lure mosquitoes significantly, and definitely not to the degree of CO2.
Other chemical matches inhibited the firing of the cpA receptor and could have use as an applied repellant, along the lines of DEET. Ethyl pyruvate is already a flavoring agent in food and is redolent of fruit, sweetness, rum, and caramel. In further studies with this chemical, mosquitoes were not able to respond to human body odor.
The research was published in the December 5th issue of Cell.
In the video below, researcher Genevieve Tauxe demonstrates the electrophysiology technique used in this study and the manner in which body odor was “collected."