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Researchers have found that the larvae and eggs of the parasitic worm that causes schistosomiasis release sugars that act like a flag, attracting the immune system and allowing them to go undetected.

The research, published in the September issue of Molecular and Cellular Proteomics, may help in the development of new treatments or a vaccine against the parasite.

Schistosomiasis, caused by worms of the genus Schistosoma, affects up to 200 million people in Africa, Asia and South America, according to the WHO.

The worms infect people who come into contact with the contaminated water by penetrating their skin. Infection can lead to liver damage, blood loss and death.

Researchers from the UK-based University of York and Imperial College London analysed sugars secreted by the parasite larvae and eggs, and discovered that many are not found in humans.

These sugar molecules cause a strong immune response in humans, co-author Alan Wilson, from the University of York, told SciDev.Net.

This is unusual, says Wilson, because parasites normally hide from the host immune system. It looks like the parasite uses the sugars to distract the immune system, so that the larvae and the eggs go undetected, he says.

Although this work is promising, Wilson says efforts on developing a vaccine have yet to bear fruit.

"If we are to beat the worm with a vaccine, we have to confront all the strategies that it uses, including this 'smoke screen' one for which we have provided a molecular basis," he says.

Wilson told SciDev.Net that future research will focus on sugars secreted by the adult parasite that can live for more than 30 years in the human blood stream.

"Obviously it must deploy some very clever mechanisms to remain unaffected in that very hostile environment," he says.

Morad Ahmed Morad, a professor of medicine at Egypt's Tanta University told SciDev.Net that this work gives insight into the lifecycle of the parasite, and could help overcome some of the difficulties associated with vaccine development.

Link to abstract of the paper

Reference: Molecular & Cellular Proteomics 6, 1485 (2007)

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