Malaria is a vector-borne disease provoked by the single-celled parasite Plasmodium, endemic in parts of Asia, New Guinea, Africa, and central and South America.
The vector of the parasite is the Anopheles mosquito.
Annually, the parasite causes disease in 400 million people and inflicts 1-3 million deaths worldwide. About 90% of the cases are in sub-Saharan Africa, where a child dies of malaria each 30 seconds. It is a disease associated with poverty and which causes poverty.
Many methods have been tried to eliminate the mosquito (interrupting this way the parasite's cycle) but they were ineffective and many times too contaminant.
Now a genetically-modified (GM) strain of malaria-resistant mosquito which survives better than disease-carrying insects has been developed. The new insect carries a gene impeding infection by Plasmodium and researchers hope that by releasing them into the wild populations, they will replace the malaria carrying type.
In lab experiments, when equal numbers of GM and wild mosquitoes were fed on malaria-infected mice, GM mosquitoes survived more and after nine generations, they represented 70% of all mosquitoes.
The researchers also put a gene for green fluorescent protein (GFP) into GM mosquitoes, which turned their eyes green phosphorescent, enabling the research team from Johns Hopkins University in Baltimore, Maryland, to distinguish easily the GM mosquitoes from the wild ones. "To our knowledge, no-one has previously reported a demonstration that transgenic mosquitoes can exhibit a fitness advantage over non-transgenics", said lead researcher Mauro Marelli.
The GM mosquitoes presented a higher survival rate and laid more eggs. But when both sets of insects were fed with non-infected blood they competed similarly.
The GM mosquitoes should survive better than wild mosquitoes even when not exposed to malaria in order to eradicate the latter. "The results have important implications for implementation of malaria control by means of genetic modification of mosquitoes. GM mosquitoes that interfered with development of the malaria parasite would make it more difficult for the organism to become re-established after it had been eradicated from a target area," they said.