Whew, that stinks!

If you've ever smelled a mosquito gravid trap, you know it's not heaven-scent. This isn't about the aroma of summer roses or the whiff of freshly baked cinnamon rolls or the fragrance of vanilla-laced skin cream.

No. This is something that stinks to high heaven. Probably low heaven, too.

It's s-o-o bad (how b-a-d is it?)  that you just want to distance yourself from the stench: you hold your nose, mutter  “P.U.” and make like a Lightening Bolt (Olympic gold-medal sprinter Usain Bolt).

Said UC Davis chemical ecologist Walter Leal:  “It smells like a latrine."

So he and his researchers set out to find a synthetic mixture that attracts mosquitoes but is odorless to humans. And they have. Their mixture, containing the compounds trimethylamine and nonanal in low doses, lures Culex mosquitoes just as effectively as the current gravid trap attractants. But look, ma, no smell!

They did it with what Leal calls "reverse chemical ecology."

The results are  published in the current edition of the Public Library of Science Journal or PLOS One.

This research could play a key role in surveillance and control programs for Culex species, which transmit such diseases as West Nile virus, encephalitis and lymphatic filariasis.

What are gravid traps? They're chemical- and water-infused traps,  sometimes called oviposition traps or ovitraps. They're meant to attract blood-fed mosquitoes searching for places to lay their eggs.  Scientists monitor these traps to determine the presence of West Nile-infected mosquitoes.

 “The gravid traps are more important (than carbon-dioxide traps) for surveillance,” Leal said, “as they capture mosquitoes that have had a blood meal and thus, more opportunity to become infected.”

Leal said that another advantage of the gravid traps is that with the capture of one female mosquito, that eliminates not only her, but hundreds of her would-be offspring. “Each female mosquito has the potential to produce about 200 eggs, and she can have as many as five cycles. So when we capture a gravid mosquito, that can remove as many as 500 females.”

Piglets shown by the UC Davis School of Veterinary Medicine are a key attraction at the California State Fair, but bees are drawing a lot of attention, too. (Photo by Kathy Keatley Garvey)The compounds used in the research, Leal said, are “simple and inexpensive” and would be of great benefit “to not only us but third-world countries where Culex quinquefasciatus is a problem.” Piglets shown by the UC Davis School of Veterinary Medicine are a key attraction at the California State Fair, but bees are drawing a lot of attention, too. (Photo by Kathy Keatley Garvey)The researchers did preliminary field testing in Davis and Sacramento but when aerial sprays mitigated the levels of West Nile virus-infested mosquitoes, they set up traps in Recife, Brazil, a city endemic for lymphatic filariasis. Leal is a native of Brazil. 

Other scientists involved in the study included UC Davis researchers Wei Xu, Yuko Ishida, Zain Syed, Nicolas Latte, Angela Chen and Tania Morgan; associate professor Anthony Cornel, associate professor of entomology at UC Davis and director of the Mosquito Control Research Laboratory, based at the Kearney Agricultural Center, Parlier; and Rosângela M. R. Barbosa and André Furtado of the Department of Entomology, Centro de Pesquisas Ageu Magalhaes-Fiocruz, Recife, Brazil.

Piglets shown by the UC Davis School of Veterinary Medicine are a key attraction at the California State Fair, but bees are drawing a lot of attention, too. (Photo by Kathy Keatley Garvey)(See more information on the UC Davis Department of Entomology Web site).