Conquering schistosomiasis in China: The final chapter

Abstract

Major control efforts over many decades have resulted in a substantial reduction in the prevalence of schistosomiasis japonica in the People’s Republic of China, although pockets of new infection continue to arise, particularly in the mountainous areas of the south. As well, the completion of the Three Gorges Dam, which crosses the Yangtze River and other large irrigation projects underway, may have significant environmental and ecological impacts likely resulting in expansion of the habitats for the intermediate snail host Oncomelania hupensis in some areas, thereby increasing the risk of human and bovine infection, and resulting in potentially new challenging consequences for control. The epidemiological picture for China will be briefly summarised and the current effective control strategies highlighted. The situation in the Philippines will also be briefly outlined but the picture is far less encouraging as there is limited national funding for schistosomiasis control; since the termination of the World Bank Loan program for schistosomiasis control in the late 1990’s, both schistosome prevalence and the associated morbidity have rebounded to former levels. Some results of recent surveillance studies we have undertaken in the Philippines will be described which indicate that schistosomiasis japonica is now far more prevalent, both in humans and bovines, than has been appreciated. Results of a large intervention trial we have completed in China - in the highly endemic Dongting Lake area downstream of the Three Gorges Dam, aimed at field-testing integrated strategies, including the use of a bovine transmission blocking vaccine, for schistosomiasis control, will be presented. The results of the trial in China will provide parameters for mathematical modelling of future control methods so as to define the long-term impact and cost-effectiveness of integrated control measures for both China and the Philippines. We believe that such an integrated approach, incorporating bovine vaccination, can lead to the future elimination of schistosomiasis from China.