Schistosomiasis is a chronic and debilitating disease that also exacerbates poverty.
The disease is endemic in the tropics and subtropics, including China.1, 2 Worldwide,
almost 800 million individuals are at risk. About 200 million people are infected,
over half of whom have various degrees of morbidity,
which leads to a disease burden that might be as high as 4·5 million disability-adjusted
life-years. This estimate of burden, however, might considerably underestimate the
true burden of schistosomiasis.
Schistosomiasis is often neglected, because it mainly affects poor rural communities
in developing countries.
In China, however, the public-health and socioeconomic importance of schistosomiasis
was recognised already in the 1950s, as documented in Mao Zedong's poem Farewell,
God of Plague.
Political will, sustained financial and technical support, and an integrated approach
readily adapted to different eco-epidemiological settings and fine-tuned over time
have substantially reduced the burden of schistosomiasis. For example, although there
were more than 10 million individuals infected with Schistosoma japonicum in 12 provinces
of southern China in the mid-1950s, this number was reduced to less than 1 million
half a century later.
In parallel, transmission was interrupted in five provinces.
However, further progress has been hampered by many factors, such as climate change,
profound demographic and ecological transformations, market-based reforms of the health
sector, and the termination of the World Bank loan project on schistosomiasis control
in 2001.5, 7, 8 Re-emergence of schistosomiasis, at least in hilly environments of
Sichuan province, is a growing concern.
At present, most schistosomiasis cases are concentrated in lake and marshland regions.
Since 2004, after the outbreak of severe acute respiratory syndrome
and fuelled by the potential re-emergence of schistosomiasis in China, the disease
has moved up as one of the top public-health priorities, and is now in the same league
as HIV/AIDS, tuberculosis, and hepatitis B.
Several features in the life cycle of S japonicum govern its epidemiology and need
to be taken into account for disease control. First, Oncomelania spp, the intermediate
host snail of S japonicum, is amphibious. These snails can, therefore, proliferate
in an array of habitats, such as networks of water in lakes and marshlands and in
different kinds of microhabitats in hilly and mountainous environments. Second, more
than 40 species of mammals can act as reservoir hosts. Domestic water buffaloes in
marshland regions are of particular relevance: these buffaloes can contribute up to
90% of the transmission of S japonicum.
The Chinese authorities noted some of these issues more than 50 years ago, which guided
the initial design of the national control programme. With the ultimate aim to eliminate
schistosomiasis, many approaches have been used, and the overall strategy has been
adapted as new approaches and evidence emerged in response to the changing epidemiology
of schistosomiasis.5, 8 Early efforts focused on the control of the intermediate host
snails and it was thought that schistosomiasis could be eliminated by chemical molluscicides
and environmental management that targeted entire snail habitats.
Large-scale community participation was a central feature in environmental management.
Although the snail habitats were substantially reduced and the number of human infections
steadily declined, the disease remained hard to eliminate.
In the 1990s, morbidity control was the backbone of disease control, helped by the
administration of praziquantel, which had been introduced for large-scale use in the
previous decade, coupled with health education. An important lesson learnt during
the 10 years of the World Bank loan project was compliance with chemotherapy, which
was dropped as the programme evolved.
This finding, coupled with factors such as severe flooding of the Yangtze river in
the late 1990s, other ecological transformations, and forced movements of population
might explain the resurgence of schistosomiasis after the project was terminated.
Indeed, the number of acute cases of human schistosomiasis and the snail-infested
areas increased at the start of 2000.
So what are the lessons from 50 years of schistosomiasis control in China? The panel
gives a summary, which we hope will stimulate the scientific community and national
schistosomiasis control-managers elsewhere. In view of the remaining challenges for
sustainable control of schistosomiasis in China, mid-term and long-term goals have
been developed: ie, reduce prevalence of infection by S japonicum below 5% by 2008
(infection control) and decrease infection below 1% by 2015 (transmission control)
in all endemic areas. To achieve these targets,5, 12 the feasibility and cost-effectiveness
of a four-pronged approach is being investigated in different settings, with the aim
of interrupting environmental contamination of schistosome eggs by human beings and
bovines. This strategy consists of: first, improved mechanisation of agriculture,
to replace buffaloes with tractors. Second, avoidance of marshland pastures and introduction
of fenced cattle-farming, as has already been done for pig-farming. Third, installation
of sanitation facilities in houses. Fourth and last, provision of toilets for mobile
populations (eg, fishermen).
Lessons from 50 years of schistosomiasis control in China
Recognition of the public-health significance of schistosomiasis
Political will and commitment to control schistosomiasis
Use of multiple interventions in integrated way
Adapt control interventions for specific eco-epidemiological settings and over time
as the challenge of control changes
Implementation, monitoring, and surveillance
Rigorous surveillance and monitoring of human and bovine prevalence and snail-infested
Preliminary data from pilot studies suggest that near-complete elimination of S japonicum
contamination is possible if such a multipronged strategy is integrated with other
Importantly, such a strategy will not only be effective against schistosomiasis but
also against a range of other helminthic diseases (eg, ascariasis, hookworm disease,
and trichuriasis) that are still rampant in China. This strategy needs to be adapted
in hilly and mountainous areas, although key challenges include the difficulty of
mechanising agriculture in hilly terrains and fencing of cattle. Cost-effectiveness
in different settings also needs to be investigated, so that schistosomiasis can eventually
be eliminated as a public-health problem in mainland China.