Typically, malaria is spread when a female mosquito bites someone who is already infected with the malaria-causing parasite Plasmodium.The parasite follows the inhaled blood into the insect's gut, where it enters the next stage of development.Once this stage is reached, it is transferred to the mosquito's salivary glands so that it can infect the next person bitten by the mosquito.
According to scientists at Imperial College London's "Transmission:Zero" project, only about 10% of parasite-carrying mosquitoes live long enough for the parasite to reachinfection stage.With this fact in mind, researchers have set out to slow the growth of the parasite in the insect's gut, so that the mosquito dies before the parasite reaches its salivary glands.
To do this, scientists genetically modified Anopheles gambiae mosquitoes - the main species that transmits malaria - so that they produce two types each time they inhale bloodThe "antibacterial peptide" molecule.Obtained from Xenopus laevis and honeybees, these molecules interfere with the parasite's energy metabolism, impairing its development.
As an added bonus, they also shorten the lifespan of mosquitoes, increasing the likelihood that the insect will die before the parasite becomes contagious.Typically, the lifespan of an adult female mosquito is about six weeks.
In laboratory tests, genetically modified mosquitoes were shown to be much less successful than regular mosquitoes at transmitting the malaria parasite.The researchers' idea is that if released into the wild, the genetically modified mosquitoes would hybridize with other mosquitoes, gradually spreading their parasite-unfriendly genes throughout the population.
Unfortunately, however, their short lifespan will put them at a distinct disadvantage in this regard - the process of natural selection will rapidly remove their uniqueness from the gene poolfeature.For this reason, scientists are looking at further engineering mosquitoes by adding "gene drives," a genetic component designed to force the spread of modified genes in a population.
Researchers plan to field test the genetically modified mosquitoes at a facility in Tanzania.To reduce the risk of damaging the ecosystem, two types of mosquitoes will be tested separately - one with only the parasite inhibitory molecule and the other with only the gene drive.If neither presents an ecological hazard, then they can be combined into a single species.
"For years, we have tried to create mosquitoes that cannot be infected by parasites, or mosquitoes that can use their immune systems to get rid of all parasites, to no avail," the research paper said.said co-author Astrid Hoermann, a postdoctoral researcher."Delaying the development of parasites in mosquitoes is a conceptual shift that offers more opportunities to block the transmission of malaria from mosquitoes to humans."
This paper was recently published in the journal Science Advances.