New model reveals pesticide-free method that takes a bite out of mosquito-borne disease

Research published in Genetics proposes a system for spreading disease-resisting genes in mosquito populations. Scientists have modeled a system that may be used to control mosquitoes and the diseases they transmit, without the use of pesticides. In the proposed system, mosquitoes are engineered to carry two genes. The first gene causes males to transmit a toxin to females through their semen. The second gene, when expressed in females, makes them immune to this toxin. This research, published in the February 2011 issue of Genetics (http://www.genetics.org), describes a system that can be created using currently available molecular tools and could confine the spread of mosquitoes to isolated populations. It also allows the genes to be recalled if necessary.

The gene transfer system was modeled using mathematical equations that describe how genetic alterations in the mosquitos' DNA are inherited from one generation to the next, and predict how these alterations will either spread or be eliminated from the population. The system has two basic components—a toxin expressed in the semen of transgenic males that either kills female recipients or renders them infertile, and an antidote expressed in females that protects them from the effects of the toxin. An all-male release should result in population suppression because wild females that mate with transgenic males produce no offspring. A release that includes transgenic females propagates the desired gene because females carrying the toxin gene are favored at high population frequencies.

The scientists used simple population genetics models to explore the utility of this gene-transfer system, and found that it can work under a wide range of conditions. It requires a high frequency of gene transfer, which is desirable because it means that genetically altered insects released accidentally are unlikely to persist in the wild. Furthermore, it means that those released intentionally can be spatially confined and that the altered genes can be removed from a population through sustained release of wild-type insects. The scientists found few technical barriers to implementing this system, increasing prospects for engineering and testing in the coming years.