Pool play. for the study, the larvae of Anopheles gambiae (presented as adults insert ) were collected in small pools of water in Burkina Faso
Kenneth Vernick. (Box) CDC
Most malaria researchers believe that most dangerous mosquito, AIA malaria parasites carrying the world's species called Anopheles gambiae , AIIS a homebody who prefers to bite people inside. But a new study challenges this view. The researchers found a large sub-population of the insect that prefers to live outdoors. These insects can play an important role, but so far hidden in malaria transmission.
"This is incredibly interesting," said Willem Takken, a medical entomologist at Wageningen University in the Netherlands. The "dogma" that malaria is transmitted mainly inside can not be correct, he said. If so, methods, Äîsuch internal control as nets and spray insecticides, Äîmay must be complemented by external strategies based.
One reason the newly discovered mosquito may have flown under the radar is that collecting mosquitoes is the hard outside and therefore rarely done, said Kenneth Vernick of the Pasteur Institute in Paris. Inside, you put a white sheet on the floor, spray insecticide on the walls and ceilings, and mosquitoes literally fall at your feet. Traps that use light to attract mosquitoes also work much better inside, said Takken.
But A. gambiae mosquito larvae begin life living in standing water. Vernick felt that some of these mosquitoes could stay outside when they become adults. His team collected A. gambiae larvae at sites along a line of 400 km in Burkina Faso, then check for a series of genetic markers currently used for typing A. gambiae . The team also trapped adult mosquitoes inside to neighboring villages.
They found that the puddles contained two different subpopulations. About 43% of larvae were genetically identical to the adult mosquitoes trapped inside houses. The remaining 57%, however, were genetically very distinct and are not found inside homes, suggesting they spend their adult lives outside. The team appointed them Goundry after a local village. The width of the genetic fracture suggests that there is little or no crossover between the groups, the team reports in the February 4 issue of Science .
Goundry mosquitoes are much more susceptible to infection with malaria: When fed blood spiked with malaria parasites, 58% were infected, against only 35% of the inhabitants of the house. This suggests that Goundry can contribute significantly to the transmission of malaria to humans, Vernick says, Äîand intense fight against malaria in the interior can actually give them an evolutionary leg up.
The researchers are not caught Goundry adult, however, and they do not know yet if they bite humans. In theory, they could feed on cattle, goats, sheep, and donkeys than people, says Vernick, in which case they would not be important for the transmission of human malaria.
"We need to know what this group is doing in terms of bite, but also in other aspects of its ecology," says Jacob Koella, an epidemiologist at Imperial evolution College London. The fact that the indoor control based methods work well in many places suggests that the outdoor mosquitoes are not major contributors to malaria, he said. Nevertheless, "this is clearly a major study"
The group Takken, meanwhile, has developed a tool that could help shed more light on the discovery. A trap that uses human scents or animal bait and which is more efficient than current methods. (An article on these traps is currently under investigation, said Takken.) with new traps, Vernick team took a lot of adult mosquitoes in the same areas Burkina Faso. He hoped that the strategy will reveal much about where exactly Goundry mosquitoes spend their adult lives, the species they feed on, and how much they contribute to deadly cycle of malaria.
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