Scientists plan to eradicate an entire insect population from an African island in a bid to stop the spread of the disease river blindness.

Rivers on the small island of Bioko, part of Equatorial Guinea, will be sprayed with insecticide in the hope that bloodsucking blackflies, Simuliidae, can be totally eliminated from the area.

The flies transmit the parasitic worms that cause river blindness.

Such an approach is only possible on islands that are far enough from the mainland to prevent the flies returning.

River blindness is endemic in many parts of Africa and South America. In some regions, up to 15% of people have been blinded by the disease.

Global effort

Because the insecticide can also kill beneficial insects or pollute rivers and water sources, researchers from London's Natural History Museum have been monitoring the island and developing a strategy that will kill the blackflies without harming the rest of the island's fauna.

Dr Rory Post told the British Association's Festival of Science he believed this was possible and that spraying would start in April next year.

The researchers will monitor the project closely to see whether the strategy is working. Blackflies left alive will be tested.

Dr Post said it was possible to tell from characters such as DNA sequence, protein structure and body shape whether insects were locally bred or immigrants.

If the spraying succeeds, it is likely to improve health conditions on Bioko dramatically.

Eradicating river blindness by treating infected people with drugs would take many years. The World Health Organisation estimates that its global elimination programme will take at least 12 years.