Confusing mosquitoes to fight mosquito-borne disease

to minute changes in carbon dioxide concentrations, they can sense carbon dioxide in our breath from long distances. Upon encountering a carbon dioxide plume, the mosquitoes orient and fly upwind, arriving eventually near us.

Most mosquito-trapping devices also use carbon dioxide to attract mosquitoes. These devices, however, tend to be expensive and bulky, and suffer from the usual difficulties associated with supplying carbon dioxide via gas cylinders, dry ice or propane combustion.

“Odor molecules that mimic carbon dioxide activity, on the other hand, can lead to the development of small and inexpensive lures to trap mosquitoes – a great benefit, especially to developing countries,” Ray said. “These highly portable, convenient and easily replenishable lures can be used wherever mosquitoes are a menace.”

The release notes that in the case of the “blinder” class of molecules, Ray’s group found that even a brief exposure to these odor molecules (presented in a blend of four odors: 2.3-butanedione, 1-hexanol, 1-butanal, and 1-pentanal) activated the carbon dioxide-sensitive neurons in mosquitoes for at least five and a half minutes, and evoked such a strong and prolonged response in the neurons that the mosquitoes’ responses to subsequent carbon dioxide stimuli were severely reduced for several minutes.

In collaboration with Ring Cardé, a distinguished professor of entomology at UC Riverside, Ray’s lab tested the effectiveness of this blend in wind-tunnels, and found that the flight of the blend-exposed mosquitoes toward sources of carbon dioxide in the wind-tunnels was disrupted.

Subsequently, Ray’s lab tested the effectiveness of the blend of odors in a semi-field study performed in Kenya in collaboration with scientists Tom Guda and John Githure at the International Centre of Insect Physiology and Ecology (ICIPE), Kenya.

The research team released Culex quiquefasciatus females in a large enclosed greenhouse that contained two hut-like structures with carbon dioxide-emitting traps placed in each of them. The researchers then included in one of the huts a source of the ultra-prolonged blend in the form of a small fan-driven odor dispenser. They found that only a few mosquitoes entered this hut and made it to the carbon dioxide trap.

“The majority of the mosquitoes were blinded by the blend, and their behavior was disrupted so that they could not detect the carbon dioxide trap,” Ray explained. “We observed no such disruption of attractive behavior in mosquitoes in the control hut — the one with just the carbon dioxide trap and no blend.”

The research was funded by a grant to Ray from the Bill & Melinda Gates Foundation through the Grand Challenges Exploration Initiative and a grant to Ray from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.

Ray was joined in the research by two members of his lab who contributed equally:Stephanie Lynn Turner, a former graduate student, and Nan Li, a former lab assistant. Collaborators Cardé, Guda, and Githure are the other authors of the research paper.

UC Riverside’s Office of Technology Commercialization has filed for patents and in 2010 licensed this intellectual property to a new start-up business, Olfactor Laboratories Inc., which has established a laboratory in the greater Riverside region for testing and development. The company, which is evaluating materials to produce insect traps and repellants that incorporate safe and effective odor-based compounds, expects the first product prototypes to be created in 2012.

— Read more in Stephanie Lynn Turner et al., “Ultra-prolonged activation of CO2-sensing neurons disorients mosquitoes,” Nature 474 (2 June 2011): 87–91 (doi:10.1038/nature10081)