Schistosomiasis in China
- Schistosomiasis is a chronic disease caused by parasitic worms.
- Globally, over 230 million people require treatment for schistosomiasis yearly.
- Globally, the number of people treated for schistosomiasis rose from 12.4 million in 2006 to 33.5 million in 2010.
- People are at risk of infection due to agricultural, domestic and recreational activities which expose them to infested water.
- Infection takes place when larval forms of the parasite – released by freshwater snails – penetrate the skin of a host during contact with infested water.
- Hygiene and play habits make children especially vulnerable to infection.
- Clean drinking water and adequate sanitation would reduce infective water contact and the contamination of water sources.
- Schistosomiasis control focuses on reducing disease through periodic, targeted treatment with praziquantel.
- Schistosoma japonicum infection remains endemic in limited areas of China, the Philippines and parts of Indonesia.
- Schistosoma japonicum is caused by trematode flatworms of the genus Schistosoma. Larval forms of the parasites, which are released by freshwater snails, penetrate the skin of people in the water causing transmission of the parasite into the host body.
- Schistosoma japonicum involves two obligatory host stages, with asexual reproduction within a molluscan host and sexual reproduction within a mammalian host.
- One feature of the life cycle of this parasite, which distinguishes it from the other human schistosome species, is that a wide spectrum of potential definitive hosts, including over 40 species of domestic and wild mammals suspected of being potential reservoirs, complicates transmission patterns.
- Repeated infection of Schistosoma japonicum leads to chronic impairment of liver.
- Schistosomiasis is in the list of category B of notifiable diseases to be reported according to the Law of Communicable Diseases Prevention and Control in China.
- China is among the target countries to eliminate schistosomiasis by 2016, according to the Regional Action Plan for Neglected Tropical Diseases in the Western Pacific (2012–2016).
- According to the Ministry of Health, in 2011, a total of 4,483 cases were reported nationwide, including 2 deaths – a decrease of 3.4% compared to the number of cases reported in 2010.
- Schistosomiasis japonicum is currently endemic in the low reaches of Yangtze River and is a major health problem among parasitic diseases.
- Bovines are generally considered to be the most important reservoirs in terms of chemotherapy-based policy in the lake and marshland regions of China. However, there are possible transmission pathways between different definitive host species.
Schistosomiasis control in China
- Three phases of schistosomiasis control have been carried out for over 50 years
- The first phase was snail control from the 1950s to the 1970s. The second phase was chemotherapy for human and animals from the 1980s to 2004. And the third phase is transmission source control, which has been going on since 2005, including snail surveys, chemotherapy for humans and domestic animals, health education, and comprehensive control engaging specialists from agriculture, forest, water conservancy and land.
- The most recent measures – since 2005 – have included: (1) mechanization of agriculture, replacing buffalos with tractors, fencing pasture areas and banning grazing in snail-infested areas, (2) improving household sanitation and access to clean water, and (3) educating fishermen and boatmen about the dangers of infested water.
- According to the State Council, in 2008, the human prevalence rate of schistomiasis in all endemic provinces had decreased to less than 5% and the endemicity in Sichuan, Yunnan and Jiangsu provinces had reached transmission control level (<1%) in 2008, 2009 and 2010.
- By the end of 2011, a total of 454 counties (cities, districts) were endemic with schistosomiasis, of which 103 reached transmission control threshold and 274 reached transmission interruption threshold.
- China aims to reach the criteria of transmission control threshold of <1% in the lake and marshland provinces and reach transmission interruption threshold in hilly provinces of Sichuan and Yunnan by the end of 2015.
- WHO’s work on schistosomiasis is part of an integrated approach to the control of neglected tropical diseases.
- WHO coordinates the strategy of preventive chemotherapy in consultation with collaborating centres and partners from academic and research institutions, the private sector, nongovernmental organizations, international agencies and other United Nations organizations.
- WHO also develops technical guidelines and tools for use by national control programmes.
- Working with partners and the private sector, WHO has advocated increased access to the drug praziquantel and resources for implementation.
- Schistosomiasis control could be a pillar of South-South collaboration between China and Africa. WHO facilitates a discussion on the transfer of Chinese expertise for schistosomiasis control to Africa.