Schistosomiasis Control and Snail Elimination in China

SCHISTOSOMIASIS (ALSO known as bilharzia or snail fever), caused by the helminth parasite Schistosoma, is a chronic, sometimes fatal, disease with serious symptoms including fever, pain, and enlarged liver. Schistosomiasis is contracted when cercariae, the form of the parasite infectious to humans, emerge from water snails, the intermediate hosts. The cercariae infect humans through skin contact with contaminated water. Then, the adult worms grow inside the human body and lay eggs that cause extensive organ damage, especially to the liver. In China, Schistosoma japonicum is the major species.

Schistosomiasis is prevalent in many parts of the world, including Africa (e.g., Egypt), Asia (e.g., China), and South America (e.g., Brazil), with more than 200 million people infected worldwide. The World Health Organization has maintained continual efforts to control the disease and set up the Scientific Working Group on Schistosomiasis to systematically study and evaluate preventive methods. In 2005, for instance, the group pointed out the deficiencies in current control strategies and proposed several new approaches.¹ In China, schistosomiasis is most dominant along and to the south of the Yangtze River, an area spanning 11 provinces (e.g., Hubei and Hunan) and one city (Shanghai), and occurs mainly in environments with poor hygienic practices.

Above: Capturing the snails, Dantu County Jiangsu Province, 1960s.

Right: Understanding what is known about schistosomiasis and adopting preventive methods.

In the early 1950s, Chairman Mao mounted a national campaign aimed at containing schistosomiasis. By 1955, widespread mass mobilization to capture the Oncomelania snails that harbor Schistosoma japonicum (see the above image),² together with effective agricultural and water conservation projects, successfully curtailed the epidemic. In fact, the snails could not be eliminated completely, but officials nevertheless had blind faith in this method.

Since the beginning of the construction of the Three Gorges Dam on the Yangtze River in 1994, schistosomiasis has reemerged as a critical public health issue in China.³ Exacerbated by poor public awareness, since 2002 infection rates have risen. It has been estimated that in 2011 more than 800 000 people in China were infected with schistosomiasis, and 6.5 million more were at risk. The annual cost of treating patients with schistosomiasis had risen to US $7.6 hundred million.

On July 8, 2004, the Chinese Ministry of Health provided important guidance for prevention programs to be launched from 2004 to 2015 in the affected provinces. The guidelines emphasize health education to raise awareness of the disease, particularly in the younger generation.⁴

This poster (see the image to the right), produced by the Ministry of Health in 2007, promotes preventive knowledge about the way schistosomiasis spreads. It highlights 3 aspects: (1) managing urine and feces, (2) eradicating snail hosts, and (3) avoiding contact with infected water. Points 1 and 3 are the most effective ways to prevent the disease, but snail elimination occupies a prominent position on the poster.

The poster does not teach the readers how to eradicate the snail hosts, nor does it specify what method to use. In fact, it is dangerous for untrained people to capture these snails, because in the process they may have contact with infected water and become infected with the parasite. Still, eradication of the snail is emphasized because the Chinese Ministry of Health maintains the emphasis of the antischistosomiasis campaign of the 1950s. This poster shows that eliminating the snail is still regarded as the most effective way to eradicate schistosomiasis. This idea is deeply rooted in the Chinese psyche.