Malaria is a life-threatening disease transmitted to humans by the bites of infected female Anopheles mosquitoes, and about half of the world’s population is at risk. Malaria can spread faster in areas where mosquitoes prefer to bite humans rather than other animals.
In a recent study from PLOS Genetics, Bradley Main of the University of California, Davis, and his colleagues investigated whether genetics influence host choice in Anopheles arabiensis. This species has become the primary vector of malaria in East Africa due to its broader host range and the frequent use of pesticide-treated bed nets, which kill off other species that live in close association with humans, leaving a bigger niche for A. arabiensis to fill.
The researchers sequenced the genomes of human-fed and cattle-fed mosquitoes in Tanzania and found that mosquitoes are more likely to feed on cattle than on humans if they carry a specific chromosomal rearrangement in their genome, reducing their odds of transmitting the malaria parasite.
“Whether there is a genetic basis to feeding preferences in mosquitoes has long been debated,” Main says. “Using a population genomics approach, we have established an association between cattle feeding and a specific chromosomal rearrangement in the major East African malaria vector.”
The study is the first to use genomic tools to find a genetic basis for earlier observations that a type of chromosomal rearrangement known as inversion can be linked to a preference for cattle feeding. While the findings provide strong support that the observed inversion in A. arabiensis is linked to cattle feeding, more testing across a larger geographic area is needed to confirm the connection.
Using genetics to better understand and track mosquito behavior could help improve local control strategies. This knowledge may also open new avenues for stopping malaria’s spread, such as genetically modifying mosquitoes to prefer cattle over people. As Main says, “This work paves the way for identifying specific genes that affect this critically important trait.”
Research Article: Main BJ, Lee Y, Ferguson HM, Kreppel KS, Kihonda A, Govella NJ, et al. (2016) The Genetic Basis of Host Preference and Resting Behavior in the Major African Malaria Vector, Anopheles arabiensis. PLoS Genet 12(9): e1006303. doi:10.1371/journal.pgen.1006303
Image Credit: Dr. Yoosook Lee, University of California, Davis CA