China's schistosomiasis scourge: Hello again, God of Plague

来源:The Economist 日期:2009-06-22

Slow progress against snail-fever

PAINT flakes off the signs that dot the shore of Poyang lake, rendering the faded red characters unreadable. But local villagers know the message all too well: “Danger! Don’t touch the water.” For fishermen and farmers whose fortunes are bound to China’s largest freshwater source, disobedience is the only option. The price is daily exposure to the water-borne, parasitic worm Schistosoma japonicum which is carried by the millions of tiny fingernail snails that infest the marshland. It tunnels through human skin, invades the bloodstream and lays eggs. Victims of schistosomiasis, also called snail-fever, suffer chronic diarrhoea, fatigue and fever. In severe cases, infection can lead to swollen stomachs, bladder cancer, liver damage and death.

It is the world’s second-most prevalent tropical disease after malaria, affecting 207m people of whom 726,000 are Chinese, according to the most recent official figures, from 2004. People around Poyang, one of the areas where the disease is endemic, laud Chairman Mao for ensuring the number is no higher. He ordered a fierce, if rudimentary, campaign in the late 1950s when cases neared 12m. Scores of peasants were told to sharpen their chopsticks and spear as many snails as they could find. The campaign reduced cases by several million in a decade and Mao penned a poem: “Farewell, God of Plague”.

As in so much else, the Chairman was overhasty. Subsequent efforts to eradicate the disease failed, despite the arrival in the 1980s of Praziquantel, a drug scientists say is highly effective in controlling the disease but fails to prevent reinfection. A note of optimism, though, sounded earlier this year. Chinese researchers announced they had reduced infection rates in two villages near Poyang to less than 1% by replacing water buffaloes, a parasite host, with tractors, and improving sanitation.

In Xinhe, one of the villages, educational posters adorn houses. The God of Longevity is plastered on the living-room wall of Hu Zhanping, the local Communist Party secretary. Next to this is a photograph of his father, who died of snail-fever 30 years ago. Mr Hu has the worm but the free medicine keeps it at bay. Next door, Mr Fu is a village anomaly: he has lived past 80. In his youth, he recalls, it was not pregnant women who had the biggest bellies, it was the men. Then they would waste away.

Mr Hu hopes Xinhe will be an example to the world. Experts say China can take a lead in tackling the disease in Asia and Africa but not before it cleans up its own backyard. Nine-tenths of the world’s schistosomiasis sufferers live in Africa and studies have shown the disease leaves sufferers more susceptible to HIV infection.

A protracted struggle beckons on the shores of Poyang and China’s other big lakes. East of Xinhe is the town of Li Hong, home to a ramshackle clinic billed as a Snail-Fever Control Centre. It still receives up to 30 patients a day. A fisherman lies groaning on a grubby bed, clutching his distended belly with one hand, clasping his wife’s hand with the other. He spends two months a year here. The medical bills devour his income, so he only seeks treatment when the pain becomes unbearable.

Residents of a 600-strong settlement outside Li Hong speak of the latest death. The diagnosis came too late; but hardly as a surprise, since 90% of the hamlet’s population is infected. Ignorance about the disease and how to treat it remains shockingly high. Some refuse to take Praziquantel, believing it will hamper their ability to work. Students and migrant workers often miss their chance of treatment. Villagers also rail against the government policy of using molluscides to kill the snails. They pay workers not to scatter the powder in the water as it depletes shrimp stocks and endangers eel farms.

Deeper flaws are emerging. Substituting tractors for buffaloes could prove too costly. The economic slowdown has driven migrant workers home, increasing populations in affected areas. But the chief concern is the impact of that emblem of controversy, the Three Gorges Dam. Scientists fear changes in water levels along the Yangzi could create new snail habitats in areas previously untouched by the disease. Ohio State University is tracking the changing shape of Poyang by satellite as it tries to predict high-risk areas. But experts agree the long-term solution is to find a vaccine. Whenever that comes, for thousands of China’s lakeside villagers, it will be too late.

    A+
声明:本文转载自其它媒体,转载目的在于传递更多信息,并不代表赞同其观点和对其真实性负责。