Mosquitoes are one of the deadliest creatures in the world. If we want to wipe out their blood-sucking buzz, perhaps some tiny-sized “birth control” is in order. In this case, that means wiping out a protein key to the formation of their delicate eggshells.
Female mosquitoes are the vectors of diseases such as malaria, yellow fever, and Zika – they feed on blood to produce eggs, which are covered in a protective shell. Tens of millions of people worldwide suffer from diseases transmitted by the insects, with millions of deaths each year, according to the World Health Organization. In a study published in PLOS Biology, researchers have conceived of a potential new route to an insecticide.
"Our goal is to help alleviate human suffering in areas of the world where mosquitoes are transmitting human pathogens," team lead Roger Miesfeld, University of Arizona (UA) professor of chemistry and biochemistry, told IFLScience.
In the lab, the UA team used an artificial glass feeder to nourish the female insects on expired human blood donated by the American Red Cross. Only the fully engorged mosquitoes were used in the study, with the females capable of laying around 100 eggs three days after such a feast.
The team discovered that a certain protein, which they aptly named Eggshell Organizing Factor 1 (EOF-1), is critical to the development of eggshells in Aedes aegypti mosquitoes. When they blocked the activity of this protein, it resulted in nearly 100 percent of females laying nonviable eggs due to a faulty eggshell layer.
More than 3,500 mosquitoes species exist, but only a few affect our health. The team made sure to identify genes unique to mosquitoes and not to loosely related insects such as honeybees. However, an RNAi injection typically only lasts for one full egg-laying cycle, but that didn't seem to be the case here. To the team’s surprise, the females could no longer produce viable eggs for the remainder of their life, even after three bountiful blood meals.
The team proposes developing a small-molecule inhibitor drug to selectively target the EOF-1 protein in regions where mosquito-borne human diseases are prevalent. This strategy may lower the chance of harming other organisms.
"DDT worked to reduce the level of mosquito-borne human disease because it broke the cycle of infection, however it also had undesirable side effects," said Miesfeld. "We propose to use a safer alternative to accomplish the same thing, which is selectively reducing mosquito populations to break the infection cycle."
But are the scientists walking on eggshells by changing the ecological landscape? Past research suggests that wiping out malaria mosquitoes (Anopheles gambiae) could be fine, although ecosystem changes will happen. However, recent research is a bit more cautious about the unintended consequences. The team themselves note that they don’t intend to eliminate mosquitoes from our ecosystem. Instead, they’d like to reduce mosquito populations at specific times of the year, such as the rainy season when disease transmission is highest.
"Eliminating any species from the ecosystem is a bad idea, even mosquitoes. Aedes aegypti mosquitoes have eggs that survive with live embryos for up to six months in between rainy seasons, which is why we think we found the EOF-1 gene to be unique to mosquitoes; these eggs are unique in that they are desiccation resistant."
"Using existing technologies to apply EOF-1 inhibitors to bed nets and sprayed around where people live is an easy transition, we just need new insecticides," added Miesfeld. Transgenic mosquitoes are another approach.
The team has taken a step to bring this discovery to the field where it is needed most, filing a provisional patent on the discovery through the UA's technology transfer office.