Scots team finds key to fever that blights Third World

Snail fever, or bilharzia, causes a chronic illness which can damage internal organs and impair growth and brain development in children.

Around 200 million people in Asia, Africa and South America are thought to be infected with the disease, which is caused by a parasitic worm.

Scientists at the University of Edinburgh have now made what they believe to be a crucial discovery about how the body defends itself against the infection.

They have pinpointed a particular type of immune cell, known as a dendritic cell, which is responsible for triggering the immune system's defence against the invading parasite.

The breakthrough came after researchers studied the immune response in infected mice. Scientists believe their findings could pave the way for new research into treatments for the condition.

Andrew MacDonald, who led the research, said: "Until now, we were unsure which of the many cells found in the immune system were crucial to fighting this parasite. We now know that dendritic cells are key to the process.

"If we can manipulate this immune response, we stand a chance of targeting the widespread suffering and chronic illness caused by this infection."

Dr MacDonald, of the university's School of Biological Sciences, said the dendritic cell is important for recognising the infection and sending out signals to neighbouring cells, "switching them on" to help fight the disease.

"We know we can say that these cells are important, and that's the starting point, but now we need to pinpoint why they're important - and that's the harder challenge," he said. "If we can identify a molecule, something that's produced by these dendritic cells that's critical for switching on the right type of protective response, then obviously we can help protect against these diseases."

Snail fever is a water-borne disease caused by flukes, or parasitic worms, found in freshwater snails in the tropics. It is common in many developing countries.

The disease, known for affecting tourists who kayak or swim in infected waters, is second only to malaria in terms of its devastating social and economic impact.

Dr MacDonald said: "Worms are just about everywhere in the world, apart from in the West, but relatively few of them are lethal. The particular species that we've been studying is a lethal infection, so there are probably about 600 million people at risk of infection from this disease. That's a huge number.

"Probably about 200 million people are actually infected.Upwards of 200,000 to 300,000 people a year are dying, just in sub-Saharan Africa, from this disease every year.

"It's a big public health problem in these socio-economically deprived tropical areas.

"These worms are also a risk to travellers. Not many people in Britain are aware of these infections, but as we become more global and travel more frequently and further afield, we get more and more exposed to these types of diseases."

The study, published in the Journal of Experimental Medicine, was carried out alongside researchers from the German Cancer Research Centre in Heidelberg.

It was funded by the Medical Research Council and the Wellcome Trust.