The very real prospect that drug resistant strains of nematodes may appear drives an urgent need to understand...where the resistance is occurring

Lyndy Holden-Dye, Southampton University

The worm has been under the spotlight in the past as the first animal to have its whole DNA sequenced.

The disease is caused by an infestation of nematodes and affects more than 20 million people in parts of Africa, Central and South America.

It is transmitted from person to person by small, fiercely-biting black flies which breed in, and always remain near, fast-flowing streams.

Lyndy Holden-Dye, lecturer in physiology and pharmacology at Southampton said: "Parasitic worms infect around a quarter of the world's population and in some African villages about 90% of children are affected.

"The very real prospect that drug resistant strains of nematodes may appear drives an urgent need to understand...where the resistance is occurring."

She said that currently the only treatment available is a mass chemotherapy programme using the drug Ivermectin.

River blindness affects more than 20m people

The drug is also used in veterinary medicine and immune strains of nematode have already appeared in animals.

Concerns are growing that the same problem will start occurring in humans.

The scientists have received funding from the Biotechnology and Biological Sciences Research Council (BBSRC) to find out how the drug works and how resistance to it might develop.

Their research is part of international efforts - sponsored by the World Health Organisation - to save millions from the effects of river blindness and other tropical diseases.

River blindness, or onchocerciasis, causes lumps or nodules under the skin, each of which contains at least one male and one female adult nematode.

The female releases thousands of microscopic worms that are carried throughout the body in the bloodstream causing tissue damage.

If they enter and die near the eyes the reaction can cause blindness.