Insecticide malaria impact clue

05 Feb 2009
BBC News
UK scientists have identified genetic differences in malarial mosquitoes which may reveal their level of resistance to insecticides.

The find may help researchers work out which areas cannot rely on insecticides to help minimise the risk of malaria, reports the journal Genome Research.

The Liverpool School of Tropical Medicine team linked two genes in one type of African mosquito to resistance. Another UK expert said similar genes might be at work in other varieties.

Malaria kills more than a million people every year in tropical and sub-tropical parts of the world.

It is caused by a parasite carried by mosquitoes, which is passed on to humans when the mosquitoes feed on their blood.

Those working at the front-line of malaria prevention in Africa and elsewhere have long relied on the pyrethroid insecticides, which are sprayed inside homes and on bed netting designed to keep mosquitoes at bay.

However, the rise of resistance in recent years has meant that pyrethroids are not as effective as they used to be.

Alternative insecticides are available, but it currently requires time-consuming testing to work out whether they are needed to tackle resistant mosquitoes in a particular area.

The Liverpool discovery could make that decision easier by allowing a simple genetic test on small numbers of mosquitoes.

Quicker and simpler

Researchers focused on the Anopheles funestus mosquito, one of the major carriers of the malaria parasite in large parts of Africa.

By studying strains of An. funestus known to be resistant to pyrethroids, and comparing their genetic code to those which have no resistance, they narrowed down the genetic differences to a couple involved in getting rid of toxins.

Dr Hilary Ranson, one of the lead authors of the research, said: "Routine use of these molecular markers for resistance will provide early warning of future control problems due to insecticide resistance and should greatly enhance our ability to mitigate the potentially devastating effects of resistance on malaria control."

Dr Jo Lines, from the London School of Hygiene and Tropical Medicine, agreed and said there was a good chance that the genetic variations would also be found in An. gambiae, the other major malaria carrying mosquito in Africa.

He said: "This is very important work. It is currently very time-consuming to test mosquitoes for their resistance to insecticides - this would allow a far simpler and quicker test to be carried out. "This is the first case in which we have been able to pin these genes down definitely."