Jan 8, 2009

Lifestyle - Toilet-Trained Fishermen Help Cut Snail-Spread Parasite Disease

Simeon Bennett

Jan. 7 (Bloomberg) -- Chinese fishermen who defecated into containers on their boats instead of the lake helped slash infections from a debilitating disease spread by snails, according to a study in the New England Journal of Medicine.

Removing cattle from snail-infested grasslands and improving water and sewer systems also reduced cases of schistosomiasis by as much as 94 percent in two Chinese villages, said researchers led by Wang Long-De at China’s Ministry of Health. The government has since adopted the measures. The malady can cause kidney failure, bladder cancer and learning difficulties in children.

Eliminating schistosomiasis, a disease the study said “just will not go away,” will take drug treatment, water management, sewage treatment and snail control, wrote Charles King, a professor of international health at Case Western Reserve University in Cleveland.

“Human treatment alone cannot prevent the environmental transmission of a parasitic disease,” King wrote in a commentary in the journal. “The elimination of schistosomiasis will be a long-term process requiring a long-term investment” and “decades-long commitment.”

Schistosomiasis, the world’s second-most-common tropical disease, after malaria, affects about 200 million people worldwide, according to the Geneva-based World Health Organization. In China, infections fell to about 726,000 people in 2004 from 11.6 million in the mid-1950s, Wang and colleagues wrote. Further progress reducing infections “appeared to be stagnating,” they said.

Parasitic Worms

The disease is caused by parasitic worms called schistosoma that grow in some freshwater snails. The worms leave the snails and enter the water, where they can penetrate the skin of humans who are wading, swimming, bathing or washing. The worms lay eggs inside people’s bodies, and the eggs can travel to the liver or intestines. When infected humans or animals defecate or urinate in water, the cycle begins again.

Over a 30-month period, the researchers removed cattle from snail-infested grasslands, built wells, toilets and public latrines and supplied tap water to two villages near Poyang Lake, China’s largest freshwater body. They also gave fishermen containers in which to defecate and urinate.

In one village, infections fell to 0.7 percent of people in October 2007 from 11.3 percent in November 2004. In another, infections fell to 0.9 percent. There was “no sustained decline” in infections in two other villages where no changes were made, the study said.

The number of worm-carrying snails in previously infested grasslands also fell, and the infection threat from lake water was eliminated, the study said.

Strategy Adopted

China’s government, aiming to reduce infections to less than 1 percent by 2015, has adopted the measures used in the study as a national strategy. The government has begun the controls in more than 90 counties in five provinces where the disease is endemic, the authors wrote.

“We believe that the new national strategy can substantially reduce the burden of schistosomiasis in China,” the study said.

To contact the reporter on this story: Simeon Bennett in Singapore at sbennett9@bloomberg.net

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