JANUARY 7 2009 23:29h
Although there are effective drugs, people tend to get infected repeatedly because they are constantly exposed to the parasite.
In China, schistosomiasis -- its scientific name -- is primarily caused by the parasite Schistosoma japonicum. Victims suffer fever, abdominal pain, cough, diarrhoea, fatigue and distended bellies in advanced stages of the illness, which renders them too weak to work.
Although there are effective drugs, people tend to get infected repeatedly because they are constantly exposed to the parasite, which thrives in paddy fields, freshwater lakes and rivers.
In an article published in the New England Journal of Medicine, the scientists described how they broke the life cycle of the parasite in four Chinese villages by replacing cattle, a key host of the parasite, with tractors from 2005 to 2007.
At the same time, villagers were given the drug praziquantel to flush the parasite from their bodies.
Both measures were necessary because infected people and cattle shed the parasite in their stools, which in turn infect freshwater snails in paddy fields and lakes.
These snails shed larvae, which tunnel through tiny pores on the skin of cattle and people, causing repeat infections.
"The central message was the need to isolate cattle from the grasslands and to improve sanitation for villagers because bovine and human feces are sources of ... infection in snails, which in turn cause infection in humans and cattle," the scientists wrote.
Villagers were later examined and experts found the rate of infection fell to 0.7 percent from 11.3 percent in one village, while the rate fell to 0.9 percent from 4 percent in another.
The number of infected snails in sampling sites also fell to 0.1 percent from 2.2 percent in a grassland area, while the rate in another site fell to zero from 0.3 percent.
"These interventions have been adopted as the national strategy to control schistosomiasis in China," the article said.