Mass chemotherapy of Clonorchis sinensis infection in Korea was started in 1982 with 40 mg /kg body weight single dose administration scheme of praziquantel.
The purpose of this study was to investigate the efficiency of current mass chemotherapy project and compare the epidemiological changes in endemic area of Clonorchis sinensis.
This study was performed at Kimhae -city and Samrangjin-eup of Miryang-gun, Kyongnam province, highly endemic area of C. sinensis located southeastern part of Korea from July to October of 1986. The therapy project of Kimhae area was performed in 1984, whereas that of Samrangjin was done in 1985 by stool examination of the Korea Association for Parasite Eradication(KAPE) and drug administration of local health centre.
The results obtained were as follows;
1) As a results of stool examination from 234 specimens obtained in Kimhae area, the infection rate has decreased to 342% from 45.6% in 1983, but the
infection rate of C. sinensis from 341 specimens obtained in Samrangjin area did not decrease (581% in 1986, 49.0% in 1983).
2) The study in Kimbae area showed that the average EPG decreased remarkably from 4,858 to 1,340 and those classified above the category of heavy infection decreased also from 14.0% to 1.7%. The study in Samrangjiin area showed that the average PPG did decrease drastically from 9,597 to 6,498 and those classified above the category of heavy infection did not go down drastically from 252 to 142%.
3) The study in Kimhae area showed decrease of Cs-D. 5D in comparison to that in 1983, wheareas Cs. D.so in Samrangjin area showed no much difference compared to that in 1983.
The intensities of endemicity were represented with the regression equation calculated with the cumulative percentages of FPG count. Regression equation was Y = 4.49-1-119 log x in Kimhae area and Y= 3b6+127 log x in Samrangjin area.
4) The two stage catalytic model was applied and the calculation lead to the equation Y=5.33(e-0.010t-e-0.016t) Khnhae area and Y=1.25(e-0.010t-e-0.016t) in Kimhae area and Y=125(e-0.010 t ?e-0.050t) in Samrangjin area.
5) The infection rate of cercaria in P.manchouricus studied in Kimhae area showed 1.25% which is not much different from that in previous years, wheare as the infection rate of metacercaria in P. parva studied in the same area this year showed 2.5- 202 /gm of flesh in comparison to 64/gm of flesh in 1983.
6) Data of C. sinensis infection on the reservoir host in Kimhae area showed 4 out of 18 dogs, 1 out of 18 rats and that in Samrangjin area showed 2 out of 18 dogs respectively.
7) Among the inhabitants who were under mass chemotherapy in Kimhae area, 71 out of them, upon stool examination, showed infection rate of 66.2% and those classified above the category of heavy infection, 2.4%.
In comparison to infection rate of 33.7% and those classified above the category of heavy infection, which is 1.0%, obtained from those not under mass chemotherapy showed higher infection rate and somewhat equal distribution of intensity of infection. The above statements reflect the fact that individual therapy besides mass chemotherapy was prevalent in that area.
8) On the other side, the studies in Samrangjin area showed infection rate of 6&7% and those above the category of heavy infection, which is 6-1%, in comparison to infection rate of 58.3% and those above the category of heavy infection, which is 16.5%, in those not under mass chemotherapy. the above reflects that although a good deal of inhabitants were classified under light or moderate infection category, those above the category of heavy infection, yet, numbered a lot, and individual chemotherapy has not been going on.
In conclusion, it was suggested that the number of re infected inhabitants among those under mass chemotherapy were numerous. Accordingly, the reinforcement of health education should be followed with mass chemotherapy. The facts of high infection rate exemplified by 65% and high number of those above the category of heavy infection in Samrangjin area say that reevaluation of dosage, number of medication and intervals should be necessarily made.
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