Effect of Control Strategies on Prevalence, Incidence and Re-infection of Clonorchiasis in Endemic Areas of China

Abstract

Clonorchiasis is a liver fluke disease prevalent in East Asia, which is transmitted to humans mainly by eating raw freshwater fish. It induces various complications in the liver or bile duct including cholelithiasis, cholecystitis, cholangitis, and cirrhosis. Clonorchis sinensis has been known to cause cholangiocarcinoma, and is still a major health problem in endemic areas. People in endemic areas are repeatedly infected with C. sinensis, as they continue to consume raw freshwater fish in spite of control activities and availability of a highly effective drug, praziquantel. Reservoir hosts such as cats, dogs, and pigs supply eggs continuously to the environment and act as a source of infection. The present study analyzed the data produced by the Korea-China collaborative project for helminthiasis control in China during 2001–2004 to find out effective chemotherapeutic control strategies with praziquantel in endemic areas and to evaluate their effects on the transmission of C. sinensis infection by repeated mass or selective treatment. The four-year control trial found that repeated treatment is essential to the effective reduction of prevalence and infection intensity in heavily endemic areas. Mass chemotherapy is more effective than selective treatment, and more repeated treatments produce better outcomes in clonorchiasis control. Health education to change the habit of consuming raw or undercooked fish is an important and practical measure to prevent and reduce human infections in endemic areas. Together with chemotherapy, health education could be highly effective and produce sustainable effects in clonorchiasis control. Treatment of reservoirs, if applicable, will contribute to reduce the source of infection