Birth control methods for mosquitoes – combatting infectious diseases

Birth control methods for mosquito's – combating infectious diseases
© iStock/Mukhina1

University of Arizona, USA, have discovered a protein that prevents mosquitoes from hatching – could such birth control methods be developed into drugs for mosquito populations?

Researchers at the University of Arizona (UA) have discovered a protein in mosquitoes that is critical to the process of producing viable eggs, and this research could be the birth control methods we need to control mosquito populations.

Depending on where an individual lives in the world, the buzz of a nearby mosquito can be a nuisance, or it can be deadly.

Birth control methods for mosquitoes

Worldwide, more than 500 million people suffer from diseases transmitted by the blood-feeding insects, including malaria, Dengue Fever, Zika, and West Nile, and nearly a million deaths are attributed to mosquito-borne illnesses each year.

When researchers selectively blocked the activity of the protein, which they named Eggshell Organizing Factor 1, or EOF-1, in female mosquitoes, the mosquito’s laid eggs with defective egg shells, leading to the death of the embryos inside.

In the report, the research team showed that EOF-1 exists only in mosquitoes. Therefore, any drug developed to render the protein dysfunctional would only affect mosquitoes and no other organisms.

Researchers are hopeful that the approach might offer a way to interrupt mosquito egg formation, without harming beneficial insects such as honey bees and implementing such birth control methods could reduce mosquito populations in areas of human disease transmission.

Jun Isoe, research leader, explains: “We specifically looked for genes that were unique to mosquitoes and then tested for their functional role in eggshell synthesis.”

“We think there are other discoveries to be made using this same species-directed approach.”

Details of the study

Isoe first used a bioinformatics approach to search for and identify genes that are unique to mosquitoes, none of those genes were previously known with regard to their function. The research team then created small RNA molecules that specifically inhibit each of the proteins the genes code for. Known as RNA interference (RNAi) the technique works by suppressing messenger RNA molecules that serve as blueprints for proteins.

Focusing on the previously identified candidate genes one at a time, the RNAi molecules were injected into female mosquitoes right before a blood meal. Males mosquitos visit flowers to drink nectar, whereas female mosquitoes bite because they need a blood meal to produce eggs and once a female mosquito has had a blood meal, her follicles develop, and it takes three days to lay eggs.

Each individual mosquito was screened for viable offspring. Out of the 40 mosquito-specific genes the team tested, only one, the EOF-1 gene, was found to disrupt eggshell formation and result in the death of the mosquito embryo.

A female mosquito needs a second blood meal in order to produce next the batch of fertilized eggs. Usually, the effects of RNAi injection last only through one egg-laying cycle, but in the case of EOF-1, the researchers were surprised to find that treated females could no longer produce viable eggs for the rest of their two- to three-week life span, even after three consecutive blood meals, thus bringing researchers a step closer to establishing birth control methods for mosquitos.

Administering birth control methods for mosquitoes

“This lasting effect makes the EOF-1 protein a very attractive target for drugs,” says Roger Miesfeld, professor and head of the department of chemistry and biochemistry, University of Arizona.

Images obtained through electron microscopy revealed that when mosquitoes are deficient in the EOF-1 protein, the females lay eggs with abnormal-looking egg shells. Although the exact function of the protein remains to be clarified, researchers believe that EOF-1 might act as a master switch at the onset of the insects’ ability to produce viable eggs in response to a blood meal.

“The inhibitors currently available to control mosquitoes have been used for so long that the pests are becoming resistant to them,” Miesfeld adds.

“Our idea is to knock their populations down to a level where you can break the cycle of disease transmission between mosquitoes and humans.”

As a first step toward turning the discovery into an application that could be commercialised, the team has filed a provisional patent on the species-specific discovery process through the UA’s technology transfer office, Tech Launch Arizona.

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