Final Report of China-Korea Collaborative Project of Control Strategies of Clonorchiasis in Heilongjiang Pilot Areas(2001-2004)

중국 흑룡강성 간흡충증 관리사업(2001-2004)

The present pilot project was executed to recommend a strategy of clonorchiasis control in China. The pilot area of this project was Zhaoyuan, Hailin, and Ningan, Heiloagjiang province. A baseline survey subjecting 4,865 residents in Heilongjiang confirmed Zhaoyuan asa high endemic area and Hailin and Ningan as moderate endemic areas. Six different control strategies were implemented in Zhaoyuan, two were in Hailin, and one was in Ningan. Including the baseline survey and project programs from 2000 to 2004, total 63,274subject-times were examined of their feces for Clonorchiseggs, 26,680 were treated, 10,082 were screened by ELISA, and 6,130 subjects were examined of their liver by sonography. The egg Positive rates in 6 villages of Zhaoyuan were as high as 44.8% 70,0%. Following the protocolof each strategy, the subjected residents were examined of their feces and treated with 25 mg/kg praziquantel, 3 times. Except the control group, all of the villages showed 72.8% to 92.0% reduction of their original egg Positive rates at Zhaoyuan. Mass treatments of all subjected residents in 2001 and 2003 reduced the egg rate from 68.8% to18.7% and 4 annual mass treatments reduced the rate from 44.8% in 2001 to 8.7% in 2004.Selective annual treatments of egg positive subjects reduced the egg rates from 50.8% in2001 to 13.8% in 2004 or from 70.0% in 2001 to 11.6% in 2004, and two treatments in a year reduced the rate from 57.6% in 2001 to 4.6% in 2004. According to repeated treatments, EPG counts decreased remarkably. In moderate endemic areas, the original egg rates were 22.6% and 28.3% in 2001 but were 1.7% and 1.1% after 2 or 3 selective treatments. The present findings of the chemotherapeutic control of clonorchiasis prove that repeated medication is important. The reduction is directly correlated with dose of praziquantel but not with mass or selective treatments. Chemotherapeutic control of reservoirhosts has little effect on reinfection of clonorchiasis because the field along the Songhua-jiang is too wide to be impacted. ELISA confirmed many serologically positive cases to Clonorchisantigen but only a few cases were positive to other antigens (Paragonimus, cysticercus, sparganum). The abdominal soaography visualized intrahepatic bile duct dilatation and periductal echo in 2,002 of 6,070 examined subjects. In addition to these examinations and treatment, health education supplemented tㅗe control activities. The present findings prove clonorchiasis is very widely prevalent and heavily endemic along the rivers in Heiloagjiang. The results suggest that group chemotherapy with praziquantel is effective to reduce endemicity of clonorchiasis. Mass treatment without individual fecal examination is recommended in heavy endemic areas where the egg rate is over 40% while one selective treatment is effective enough in moderate endemic areas.