Studies on Filariasis in Korea -Status Survey and Chemotherapy in Cheju Do*-

Abstract

1. Based on the data collected through the night blood surveys during the period of 1972 to 1975 in Cheju Do, the present status of malayan filariasis in the island was analyzed, reviewed and compared with the results obtained in the previous survey during the past decade. 2. The present survey revealed that among 5,681 persons examined in the areas of seven Myons and two Eups, 149(2.6%) were found infected with Brugia malayi, And the mean microfilaria densi ty was 1. 40 per cmm of blood. According to the geographic distribution by villages, the south-eastern portion showed a slightly higher rate of infection. From the distribution of the positives by age, the infection rate rapidly increased at the age of 20-29 years and reached to a peak of 6. 6 per cent at the age of 40-49. 3. Compared to the present data with those collected from 1963 to 1964 by Seo et aI. (1965), the overall infection rate distinctly decreased from 8.6 to 2.6 percent and the microfilaria density also fell from 1. 91 to 1. 40 per cmm of blood. Especially, at certain villages in the south-eastern section of the island where mass treatment has been conducted, such as Namwon, Pyosun etc., the remarkable decreaaes in the rate of infection and microfilaria density have been recognized. This has been proved also in the decreased rates of natural infection of mosquito, Aedes togoi with mature larva of B. malayi. In the village of Namwon Myon, the natural infection rate of A. togoi decreased from 8.8 per cent at 1970 before mass treatment, up to O. 33 per cent at 1975 after treatment. 4. An attempt to revise the dosage schedule by diethylcarbamazine and to make the drug more practicable in the mass treatment was made. The half conventional dose, 3 mg/kg 'of diethylcarbamazine daily 12 times, totaling 36 mg/kg was chosen as a chemotherapeutic 'Course. The treatment response was analyzed on the basis of the negative conversion and reduction rates of microfilariae in the blood. Twenty-one 'Out of 38 positive cases given the above doses were converted negative after the first 18 mgt kg doses at the seventh day of treatment. Twelve out of 15 cases who undertook the follow-up study up to 250th day after treatment were completely cleared from microfilariae in the blood by a total dosage of 36 mg/kg. 5. Three dosage schedules, the conventional -dosage (6mg/kg daily, 12 times), the low dosage (0. 5, 1, 2, 4, 6 mg/kg daily boosted '6 mg/kg up to four times) and the half 'Conventional dosagetS mg/kg daily, 12 times) were compared each other in their effectiveness. The negative conversion rate as well as the microfilaria reduction rate in the low dosage schedule was slightly higher than the others. However, it is assumed that the half conventional dose may also quite effective as a smaller dose schedule. It is practically recommended that the half conventional dose may also be employed in the mass treatment of the cases with low microfilaria density. 6. The minimum dosage to clear microfilariae of B. malayi from blood in Cheju Do seems to be good enough with the dose, of 36 mg/kg of diethylcarbamazine.