Why Some Mosquitoes Have a Taste for Non-Human Blood

Link between mosquito genetics and feeding preference could lead to improved malaria control.

Scientists have discovered that mosquito meal preferences are written in their genes. Mosquitoes carrying a specific chromosomal anomaly — an inversion, in which a section of the third chromosome is flipped around — prefer to feed on cattle than human blood, according to a study published in PLOS Genetics. 

The findings could have implications for curbing malaria transmission, as human exposure to malaria is greatest when mosquitoes prefer to feed on human blood rather than the blood of other animals.

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A team of researchers collected mosquitoes in the Kilombero Valley, Tanzania. They focused on the species Anopheles arabiensis, which is the only malaria vector remaining in many parts of Africa.

By sequencing the genomes of 23 mosquitoes that fed on human blood and 25 that fed on blood of cattle, the researchers found that the chromosome inversion mattered when it came to the mosquitoes’ food choices.

In Aedes aegypti, the mosquito that spreads dengue and zika, differences among individuals in an odor receptor gene have previously been linked to preference for biting humans versus animals. But until now, no such links between genes and feeding behavior have been uncovered in the malaria-transmitting species.

"Whether there is a genetic basis to feeding preferences in mosquitoes has long been debated," study lead author Bradley Main, a researcher at the University of California, Davis School of Veterinary Medicine, said in a press release. "Using a population genomics approach, we have established an association between human feeding and a specific chromosomal rearrangement in the major east African malaria vector.”

“This work paves the way for identifying specific genes that affect this critically important trait," he adds.

Though the authors note that testing in a larger geographic area is still required to confirm the connection between the chromosomal inversion and feeding preference, they suggest that future malaria control strategies could involve selecting for genes that drive zoophily — a preference for non-humans — in wild mosquito populations.

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