Researchers Hope to Prevent Disease by Turning off Biting Behavior in Mosquitoes

This is a mock press release created with a max word count of 600 words. The paper used was Bradshaw et al. (2018) Evolutionary transition from blood feeding to obligate nonbiting in a mosquito. PNAS 115: 1009-1014. Article Link


Wouldn’t you like to enjoy your outdoor picnics without the nuisance of mosquitoes dining on you? University of Oregon researchers identified genes associated with the feeding behavior of the mosquito Wyeomyia smithii, and they ultimately hope to prevent the biting behavior of mosquitoes with this new information. They outline their findings in the January 30th issue of the Proceedings of the National Academy of Sciences. Mosquitoes are known as the world's "Most Dangerous Animal" because they spread several diseases in humans and animals by biting. Some of these diseases include Malaria, West Nile, Zika, and Dengue. In fact, nearly half of the world’s population lives in areas at risk for Malaria transmission by mosquitoes.

Wyeomyia smithii has both biting (blood feeding) and nonbiting (nectar feeding) natural populations depending on its geographic location. In general, female mosquitoes are infamous for their blood sucking behavior to develop and lay eggs. However, not all mosquitoes require blood in their diet. Some mosquito species do not require blood to lay a single set of eggs and some only require blood to lay more than one set of eggs.

The presence of two different feeding behaviors in Wyeomyia smithii led the researchers to investigate if they could select for a specific behavior. In this study, the authors took a nonbiting population from Florida (FLdis) and imposed a direct selection for blood feeding biting mosquitoes in their laboratory. After seven generations, their population exhibited 100% biting behavior (Flavid).

The researchers found the FLavid and FLdis populations of mosquitoes to have differences in gene expression. Since the FLavid population was derived most recently from FLdis, the authors associated these differences with the new biting behavior. Additionally, when Flavid was compared to a nonbiting population of W. smithii from Maine, 95% of the genes found to be differentially expressed between the two Florida mosquito populations were positively associated with genes expressed by the Maine mosquitoes. In other words, genes that were turned on or off in the biting population were also likely to be turned on or off in the nonbiting populations of Florida and Maine. Many of the genes impacted function during food metabolism and egg laying. Blood feeding mosquitoes specifically upregulate genes important for blood protein digestion and ovary development.

The question still remains as to why different feeding behaviors have evolved within the same species. Christina Holzapfel, the senior author on the paper, says “Blood feeding is not a free lunch.” Although there are nutritional benefits to eating blood, there is significant cost to the mosquito when finding and surviving on a host. First, there is the heat shock associated with consuming a warm blood meal (40°C) when mosquitoes function best at air temperatures around 27°C. Additionally, the breakdown of hemoglobin from the blood meal releases toxic heme and iron that the mosquito has to neutralize. Conversely, the authors show how nonbiting populations have different metabolic genes upregulated to use different nutrients they may encounter.

The hope is to further narrow down specific genes or pathways that are important for the evolution of the nonbiting behavior in mosquitoes. Once these are identified across different species, the idea would be to target those pathways to turn biting mosquitoes into nonbiting. Holzapfel says, “If Mother Nature has done it in the not so remote past in W. smithii, we have to think this idea is feasible for mitigating mosquito-borne diseases….Who wouldn’t also enjoy the benefit of enjoying backyard picnics in the middle of the summer without the annoyance of getting bit!"

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