New ‘outdoor’ mosquito could hamper malaria control

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[NAIROBI] Scientists from Kenya and the United Kingdom have discovered a new potentially dangerous malaria-transmitting mosquito, which they say does not behave like other mosquitoes.

The mosquito, known only as type A, was found in western Kenya and has biting patterns that the researchers say will make it harder to control than the commonly known Anopheles mosquitoes.

Anopheles mosquitoes rest and feed on humans at night indoors while this newly identified mosquito bites people outdoors earlier in the evening, soon after sunset.

Lead author Jennifer Stevenson, research fellow at the UK’s London School of Hygiene and Tropical Medicine (LSHTM), said: "80 per cent of the ‘unidentified species’ were caught outdoors, and of those, 70 per cent were caught before 10.30pm."

She told SciDev.Net that the new mosquito had subtle differences in its physical appearance to the known mosquitoes in the area, and that the researchers had been finding it difficult to definitively identify it.

The mosquito has differences in its DNA compared with Anopheles and the researchers have sent samples of the new species to the University of Notre Dame in the United States for detailed DNA analysis.

The researchers are now calling for increased surveillance of the mosquitoes to detect any change in their behaviour that might affect malaria control, as well as a focus on integrating a wider range of malaria control tools to deal with the threat of outdoor transmission.

"We still advocate universal access to and use of treated bednets. However, our study and others from East and West Africa have shown that some malaria-transmitting mosquitoes are resting or feeding outdoors. So, if outdoor transmission is shown to be of significance, it may be advisable to use a mix of interventions," said Stevenson.

Willis Akhwale, head of the department of disease prevention and control in Kenya’s Ministry of Public Health, said the mosquito could complicate the fight against malaria in Kenya and Sub-Saharan Africa.

"The new species, coupled with recent findings which show the ordinary mosquito is also changing its feeding patterns and preferring an earlier meal before people go to bed, may require new control tools," said Akhwale.

Jo Lines, reader in malaria control and vector biology at the London School of Hygiene and Tropical Medicine (LSHTM) and former coordinator for the WHO’s Global Malaria Programme, said: "These findings remind us that the basic biology of malaria transmission is subtle and complex and there are still plenty of gaps in our knowledge and local variations that we do not understand".

The research was published in Emerging Infectious Diseases on 27 August.


This article has been produced by SciDev.Net’s Sub-Saharan Africa desk.