Infertile Mosquito Study Means Good News for Malaria Research

Mosquitoes are the pesky little critters that bother people in the summer with itchy red bumps and for many in developing areas, malaria. Each year, malaria, an incapacitating parasitic disease spread through mosquitoes, affects more than 300 million people, resulting in almost 800,000 deaths. Africa is especially affected by this disease because, on average, a child dies from malaria every 45 seconds.

Currently, doctors treat malaria using a slew of medications such as chloroquine and quindine. The widespread use of chloroquine in regions like Southeast Asia and East Africa has led to a resistance to the drug and a more difficult time treating the disease. 

Medical researchers are working on eradicating malaria, but money is a limiting factor. People realize that better tools are needed to reach this goal. Recently, however, a leap in malaria research may solve the problem.  

A new study from Imperial College London, led by Dr. Flaminia Catteruccia, gives hope to the idea that scientists will be able to control mosquito populations. Researchers chose to focus on the Anopheles gambiae, the mosquito species that is most commonly responsible for malaria transmission in Africa.  The results from the study indicate that female mosquitoes cannot tell whether a male has sperm or not.

Researchers chose to focus on the Anopheles gambiae mosquito species because it is most commonly responsible for malaria transmission in Africa. The study involved observing isolated mosquito mating couples in a laboratory. Scientists looked for certain behaviors between the couples such as, whether the female laid the same number of unfertilized eggs as they would with a fertile male.

For the study, researchers created 100 spermless mosquitoes by putting a protein into regular eggs that interrupts the creation of testes in the male, thus making it impossible for the mosquitoes to produce sperm. Despite preventing the development of the testes, this did not interfere with sexual behaviors.  

Female mosquitoes only mate once in their lifetime, which is followed by a blood meal and then lays eggs.  Dr. Catteruccia’s study determined that after females mate with a sterile male, her behavior does not change, despite the eggs not being fertilized.

Originally, the researchers expected to see that the female mosquitoes had evolved a method for determining if mates are infertile so that they guarantee their eggs will produce offspring. They based this idea upon female fruit flies who are capable of mating with more than one partner.

“In the fight against malaria, many hope that the ability to genetically control the mosquito vector will one day be a key part of our armory. In order for these currently theoretical control strategies to work, we need to make sure that the insects continue to mate as normal, unaware that we have interfered with their sexual mechanisms. This study strongly suggests that they cannot tell the difference between a fertile and a spermless mate,” stated Dr. Catteruccia.

These results can contribute to malaria eradication because it can help to control the number of mosquitoes carrying malaria. The current idea is that the females would mate with males who have experienced a genetic change to make them infertile and then would not produce fertilized eggs.

Charles Godfray, a professor from the Zoology department at the University of Oxford and co-author on the study explained, “this is an exciting time with modern genetics providing a series of new ideas about how to control the major insect vectors of human disease, including the mosquito Anopheles gambiae — perhaps the single most dangerous insect species for mankind. A number of these techniques involve disrupting natural mating patterns and to get these to work a really good understanding of mosquito mating and reproduction is essential.”

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