Objective: To investigate the current prevalence of Clonorchis sinensis infection in the known endemic areas of China.
Methods: According to different endemic level and river system, the lamination stochastic group sampling was carried out in 27 Provinces/Municipalities/Autonomous Regions (P/M/A) from 2002 to 2004. Eggs in stool were examined by modified Kato-Katz thick smears method.
Result: A total of 5,230 cases of Clonorchis infection was found from 217,829 sampled population of 27 P/M/A, and the mean prevalence was 2.40% by which the number of infected people was estimated to be 12.49 millions. The geometry mean worm egg density was 2,208 EPG (stool). Light, moderate and heavy infection occupied 78.93%, 17.40%, and 3.67% respectively. Infection was found in 19 out of 27 P/M/A investigated, with the highest prevalence in the provinces of Guangdong (16.42%, 2,278/13,876), Guangxi (9.75%, 1,365/13,990) and Heilongjiang (4.72%, 636/13,458). Males showed higher prevalence (2.94%, 3,267/111,262) than females (1.84%, 1,963/106,567). There was infection in all age groups,with the highest prevalence in the group of 50 to 59 years (9.16%). By occupations, more infections were found in businessmen (13.42%, 124/924), followed by factory workers ((7.9%, 298/3,773), and retirees and veterans (5.28%, 70/1,327). Adults showed heavier infection in some provinces where the main infection way was raw fish-eating, but in children in other provinces. For geographical distribution, the terrain in network of rivers and lakes showed higher prevalence (5.23%, 687/13,125) than the hilly terrain (2.34%, 1,111/47,552). Prevalence showed family-aggregation feature.
Conclusion: Clonorchiasis is widely endemic in China with a high prevalence in some provinces. Male adults have been more involved with a family aggregation.