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mosquitoes resistant malaria - recognizable in this image by the green fluorescence of their eye facets -. fare better when feeding on infected blood
Johns Hopkins University
If you want to protect people against malaria, the disease keep on mosquitoes. It is an interesting approach, but its implementation is more difficult than it sounds: In nature mosquitoes malaria-free tend to be less well than their susceptible counterparts. Enter a genetically modified mosquito to fight against the disease. A new study, transgenic insects beat mosquitoes nonengineered when both feed on the blood of infected parasites. If confirmed, the study means that the plans to replace the entire populations of mosquitoes with those resistant to disease may have better chances of success.
After mosquitoes bite a host with malaria, the parasite that causes the disease proliferates in the insect, is preparing to infect the next human victim. It is not fun to be infected, and one would think that mosquitoes have developed resistance to the malaria parasite over time. But several studies have suggested that mosquitoes designed to build defenses against malaria are less fit than the insects that have chosen to live with pests.
Now it is necessary to take heart. It several years ago, a group of medical entomologists at Johns Hopkins University has created a strain of Anopheles stephensi (a mosquito that bites rodents) with a gene called SM1 makes the mosquitoes resistant to infection Plasmodium berghei , a parasite of rodents malaria. In the new study, published online this week in Proceedings of the National Academy of Sciences , the group conducted a series of experiments in which 250 of these insects were placed in a cage with 250 counterparts wild type and allowed to feed on mice infected with malaria. Resistant insects lived longer and produced more eggs than those who lived not resistant to the parasite, and after nine generations, some 70% of the population was resistant. Researchers think the realization SM1 is a cheaper strategy than what the defenses against mosquitoes resistant to malaria develop in nature.
Yet the apparent benefits of resistance may not be large enough to help the spread of genes in a population in the wild, where all hosts are infected, says co-author Jason Rasgon. However, he said the study is the first demonstration that natural selection can help, rather than harm, genetically insects. And mosquitoes with SM1 gene could help keep malaria when he was licensed from an area using other means, such as bed nets, drugs, or future vaccine, he adds.
entomologist Bart Knols of Wageningen University in the Netherlands warned that the conditions of the cage are very different from those of the field where many other factors affect the survival of an insect; what is more, the results may not hold in the human malaria, he said. Yet it is "very encouraging" to see if mosquitoes engineering laboratory made in the edge of evolution, said Kenneth Vernick of the University of Minnesota
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