Bed nets and insecticides that are used to control malaria, could fail to fully protect the population, scientists have warned following the discovery of a potentially dangerous new malaria-transmitting mosquito in Kenya.



The London School of Hygiene and Tropical Medicine, which made the discovery recently, said the new species had never been linked to the transmission of malaria before.



The commonly known Anopheles mosquitoes transmit malaria by generally resting indoors and feeding on humans at night. The new mosquito, however, was found to be active outdoors and bites people earlier in the evening soon after sunset.

"We observed that many mosquitoes we caught, including those infected with malaria, did not physically resemble other known malaria mosquitoes," lead author Jennifer Stevenson who is also a research fellow at the London School of Hygiene and Tropical Medicine said in the study document.

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Analysis indicated that their DNA differed from sequences available for known malaria-transmitting mosquitoes in Africa.

"These unidentified mosquitoes are potentially dangerous because they are outdoor-active and early-biting, and so may evade the current indoor-based interventions to control mosquitoes.

"In this way, they may prevent the complete suppression of malaria transmission in the area."



The study was carried out in a village in Kisii in the highlands of western Kenya, an area with seasonal and unstable malaria transmission. It was aimed at outlining how researchers set up indoor and outdoor mosquito traps.



The Kenya Medical Research Institute under the Malaria Transmission Consortium, funded by the Bill and Melinda Gates Foundation carried out the study.

Over 65 percent of mosquitoes caught were outdoors and 348 mosquitoes were identified using DNA sequencing techniques of which over 40 percent were found to be of this unidentified species.



The researchers called for increased entomological surveillance and a focus on integrating a wider range of malaria control tools to deal with the threat.

Malaria is the leading cause of death in Africa. And about 25 million people out of a population of 34 million Kenyans are at risk of contracting the disease.



"These findings remind us that the basic biology of malaria transmission is subtle and complex: there are still plenty of gaps in our knowledge, and local variations that we do not understand," the researchers said.

"We do not yet know what these unidentified specimens are, or whether they are acting as vectors on a wider scale, but in the study area they are clearly playing a major and previously unsuspected role.

"The practical implication for malaria control programmes is that there is no substitute for careful monitoring of mosquito populations.

"In order to be effective, such monitoring must be carried out by specialist experts who have the skills to recognise and investigate unexpected entomological observations," Jo Lines,  a researcher in malaria control and vector biology at the school said.



The findings are reported in emerging infectious diseases. 

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