Tricking the mosquito’s “nose”  pg. 5

The project’s goal is to develop the first target BDOCs in late 2006, and deliver them for testing in Tanzania the next year.

Zwiebel and his colleagues decided to work on chemical interventions, as opposed to the genetic approaches proposed by some of their colleagues, in part because they feel that chemical methods will be adopted more readily by the people who live in the areas where malaria is endemic.

“There is a long history of chemical intervention and insecticides,” Zwiebel says. “People have been slapping everything from mud to animal feces all over themselves for thousands of years to protect themselves from insect attacks.

“We are essentially bringing 21st century technology to a very well-established set of paradigms. I don’t think we have to convince many people that developing new, safe, economically effective repellants is a good idea.”

Surgical strike

Other Grand Challenges projects are pursuing genetic strategies to interfere with the ability of mosquitoes and other insects to transmit diseases. There are concerns, however, that development and release of transgenic insects may have unpredictable and undesirable ecological consequences.

In comparison, the Vanderbilt-led team is trying to target the mosquito’s sense of smell with compounds that will have a minimal impact on the environment. “We don’t have to worry about making an environmental faux pas with regard to releasing something that is never coming back,” Zwiebel comments.

The potential of an olfactory strategy has been demonstrated by the use of scented baits to kill the African tsetse fly. The program, which has replaced the practice of treating large tracts of land with persistent insecticides, is widely considered to be an environmental and technological success.

“One of the concerns that we have from an ecological point of view is to only target the disease vector mosquitoes that we want to repel,” says Zwiebel. “Many insects play critical roles in ecosystems in agricultural and other contexts that we do not want to affect unnecessarily. This can be potentially very devastating.”

Instead, the researchers are focusing on the receptors they have characterized that are considerably different from those found in other insects. They figure that this gives them the opportunity to develop a “surgical strike capacity” that will target the Anopheles mosquito and leave all of the other insects alone.

“We are not talking about eradicating anything and we are not talking about species replacement. We want to take as ecologically benign an approach as possible in order to reduce the contact between humans and Anopheles mosquitoes. That is where our interest ends,” Zwiebel says.

Fortunately, he and his colleagues have plenty to work with. They have characterized 77 novel odorant receptors as potential targets. Not only does this increase the odds that they can find odorant blends which are highly selective, it also gives them an opportunity to eliminate the problem of resistance.

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View Related Article: How to trick the mosquito's nose: Malaria control at the molecular level