New Mosquito Subgroup is Highly Susceptible to Malaria-Causing Parasites
Most studies of malaria vectors, such as Anopheles gambiae, have focused on mosquitoes that rest indoors, since they are more likely to have contact with humans and transmit the malaria parasite. Larval stage and outdoor-resting mosquitoes are not as well-studied because they are more difficult to find and collect.
Differences Between Outdoor- and Indoor-Resting Mosquitoes
Because outdoor- and indoor-resting mosquito subgroups live in such separate environments, they do not interbreed and have grown to differ genetically. For example, multiple recent studies have documented the beginnings of speciation between A. gambiae subgroups M and S, but this emerging speciation is taking place only among indoor-resting mosquitoes. In a NIAID-funded study published in February 2010 in the journal Science, researchers collected and genetically analyzed A. gambiae larvae from three village sites in Burkina Faso. The investigators were led by Kenneth Vernick, Ph.D., of the Institut Pasteur in Paris.
What These Differences Could Mean for Malaria Control
Analyzing the genomes of the larvae, they found two A. gambiae subgroups. One was genetically indistinguishable from indoor-resting adult mosquitoes in the Burkina Faso area, but the other did not match any subgroup of adult mosquitoes that had been described so far. The researchers found that mosquitoes belonging to this second group, named GOUNDRY after the area in which they were found, were much more susceptible to the parasite that causes malaria; the prevalence of Plasmodium falciparum infection among GOUNDRY mosquitoes was 58%, compared to 35% among the indoor-resting mosquitoes.
Although there is no evidence of GOUNDRY mosquitoes biting humans, any human feeding by these mosquitoes is of concern. Also, it should be noted that current malaria control measures such as bed nets and insecticide spraying focus on indoor-resting mosquitoes and are less effective against outdoor-resting subgroups.
Reference:
Riehle MM, Guelbeogo WM, Gneme A, Eiglmeier K, Holm I, Bischoff E, Garnier K, Snyder GM, Li X, Markianos K, Sagnon N'F, Vernick KD. (2011). A cryptic subgroup of Anopheles gambiae is highly susceptible to human malaria parasites . Science. 331(6017):596-598.