Mosquito genes affecting malaria transmission in Africa revealed

Field study shows switching off a gene inhibits parasite growth<em> - News</em>

By Danielle Reeves
Wednesday 28 May 2008

Mosquito genes that control how many malaria parasites can successfully develop inside the body of the mosquito have been identified by researchers, according to new research published this month in the journal PLoS Pathogens.

The parasites that cause malaria develop inside the bodies of mosquitoes for almost three weeks before they are transmitted to humans when the mosquito bites and takes a human blood meal.

Now in a field study in Cameroon, researchers have shown for the first time that if particular mosquito genes are deactivated, the number of malaria parasites that are able to successfully grow and develop inside the body of the mosquito can change dramatically.

Over half the school children tested in the Cameroon study were infected with the malaria parasite

The researchers hope that understanding the roles different mosquito genes play in controlling the growth of malaria parasites may one day lead to new ways of stopping the transmission of the disease.

Lead author of the paper, Dr Dina Vlachou from Imperial College London's Department of Life Sciences, explains: "This new research gives us an important new insight into how different genes in the mosquito's body can affect how well malaria parasites can grow inside it. The more we know about the complex relationship between malaria parasites and mosquito hosts in real-world scenarios, the better our chances are to develop ways to combat the disease."

Dr Vlachou and her colleagues at Imperial carried out the new research in collaboration with scientists from France and Cameroon. They collected blood samples from over 3,000 school children from a small town in Cameroon, and found that over half were infected with the deadly malaria parasite called Plasmodium falciparum, with 6 per cent of the infected group carrying parasites that transmit the disease.

The scientists then allowed mosquitoes in which specific genes had been switched off to feed on the infected blood. They then monitored how well the parasites fared inside the bodies of these genetically modified mosquitoes.

Their study showed that turning off a gene which plays a role in moving fats around the mosquito's body dramatically reduced the parasite's ability to develop. Conversely, the researchers showed that if they turned off a different gene which regulates the 'scaffolding' of mosquito cells, the number of parasites successfully developing increased over four-fold.

Understanding how manipulating these two genes has contradictory effects on the parasite's growth gives researchers a greater insight than before into the parasite/host relationship.

Dr Vlachou says the results prove for the first time that mosquito genes identified in lab experiments, and tested using malaria parasites that infect animal models, have the same effect on human parasites circulating in the blood of infected children in Africa.

Malaria is an infectious disease that threatens half the global population. Almost half a billion people are infected every year, and of those between one and three million die – mostly children under five in Africa.

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