Epidemiological investigation on Clonorchis sinensis in human population in an area of South China.

To detect the prevalence of Clonorchis sinensis, one of the important helminthes in the human population of the Guangxi Region where Schistosoma japonicum was endemic but eliminated in the late 1980s, the Kato-Katz thick smear technique was used for examining fecal samples from selected townships in Hengxian County. Among 1,552 people examined, 491 (31.6%) were found infected with C. sinensis. By counting eggs per gram feces (EPG), it was found that the light, moderate, and heavy intensities of infection occupied 55.4, 33.0, and 11.6%, respectively, with an average EPG of 4,845 in the infected subjects. The survey revealed that the prevalence in the age groups of 0 - 9 and 10 -19 years old was less than 10% but was 45 - 50% in the groups between 30 - 39 and 60 - 69 years old. A much higher prevalence was demonstrated in the male population (41.9%) than in the females (20.5%), and heavier intensity of infection was also found in the males than in the females. These results indicated that the prevalence of this liver fluke is increasing in the past decade in that region, and there is an urgent need to further assess the epidemiological factors in reference to the area's changing socioeconomic conditions and human behavior, contamination of the environment and fish ponds, inadequate farming/fishery practices, and the infection of domestic animals.