Objective: To make an epidemiological investigation on clonorchiasis sinensis and relevant factors in the south of Hunan Province.
Methods: One village from each of Lengshuitan District and Qiyang County was selected for the survey from November to December in 2006. Stool samples from villagers were collected and examined by modified Kato-Katz method. Questionnairing was performed for relevant knowledge and attitude among residents. The infection rate in animal reservoirs and intermediate hosts were detected.
Results: A total of 586 cases with Clonorchis sinensis infection were found from 777 people with a prevalence of 75.4%. The average egg density was 451 eggs per gram (EPG) feces. Light, moderate and heavy infections occupied 85.5% (501/586), 14.0% (82/586), and 0.5% (3/586) respectively. Prevalence in males and females was 76.9% (316/411) and 73.8% (270/366) respectively with no significant difference (chi2 = 1.013, P > 0.05). Infections were found in all age groups, with the highest prevalence in the group of 70 to 79 years (85.7%, 30/35). By occupations, the prevalence was 82.5% (447/542) in peasants, 79.3% (42/53) in doctors, 73.7% (28/38) in teachers, and 73.5% (25/34) in local cadres. The infection rate was 17.4% (29/167) and 7.4% (2/27) in Parafossarulus seriatulus and Alocinma longicornis, and 69.2% (9/13) and 5.3% (1/19) in Carassius auratus and Cyprinus carpios respectively. Adult worms were found in all 3 dogs dissected. Over 80% inhabitants did not know that this disease can be acquired by eating raw fish. 95.6% (153/160) of the farmers and 56.7% (349/616) of the students had a history of eating raw fish. The water was contaminated with C. sinensis eggs by using untreated feces as fertilizer for farming and by scrubbing pail latrines in the ponds.
Conclusion: The prevalence of clonorchiasis in human population is high in Lengshuitan District and Qiyang County of Hunan Province. Eating raw fish and using untreated feces as fertilizer are the most important epidemiological factors of the disease.