Model of schistosome infection is created

Hong Kong -- Scientists have found a parasitic infection common in China and Southeast Asia could be effectively reduced by controlling snail populations.

Schistosomiasis infection with schistosomes of various species affects some 200 million people worldwide, and can cause serious chronic illnesses, including liver failure.

Steven Riley of the University of Hong Kong and colleagues analyzed infection patterns of the parasitic worm Schistosoma japonicum in 50 Philippine villages and found differing rates of infection among humans and animals.

The researchers then developed a mathematical model incorporating fecal parasite test results from thousands of people and animals to explain the differences.

Schistosomes, the scientists said, are passed from mammals to fresh-water snails via feces, and then cycle back to infect mammals that contact water inhabited by infected snails. Using their mathematical model, the team found transmission from snails to mammals was a more important factor in explaining the differences among villages than was transmission from mammals to snails.

Riley said the findings suggest reducing the snail population and the exposure of mammals to parasite-containing water might reduce human infection levels more effectively than interventions interrupting other parts of the parasite's life cycle.

The research appears in the journal PLoS Medicine.

Copyright 2008 by United Press International.