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Korean J Parasitol > Volume 12(1):1974 > Article

Original Article
Korean J Parasitol. 1974 Jun;12(1):8-13. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1974.12.1.8
Copyright © 1974 by The Korean Society for Parasitology
A follow-up study to evaluate the efficacy of mass chemotherapy for control of paragonimiasis
Joung Soon Kim and F. B. Bang
Department of Epidemiology, School of Public Health, Seoul National University, Korea.
Department of Pathobiology, School of Hygiene and Public Health, The Johns Hopkins University, USA.
Abstract

In the survey of l1,005 subjects in l3 villages of Che Ju lsland, 1,450 persons were egg-positive by repeated sputum examinations. The response rate to intradermal test ranged 50-80% of the population and to sputum examination for skin positive 60-70% in the first survey done in l964. 93% of all egg-positive was treated with 40 mg/kg body weight of bithionol on alternate days for 10-15 doses in l965. Follow-up studies were carried out in one year, three-year, five-year, and eight year after the mass treatment. The one year follow-up study covered 86.5% of all treated cases in all villages but only a part of the population of a few villages in further follow-up studies. In this paper only the result obtained from the age group of 7-18 years, the common population studied in every follow-up for the purpose of comparison, is presented. Intermediate hosts of P. westermani were examined at the same time. In one year follow-up it was found that 91% of egg-positive treated became negative.

Three parameters, skin reaction, sputum examination, and infection status of intermediate hosts by area and year were used for comparison. Skin positive rate showed gradual decrease with more marked drop in Kang Chung where more thorough survey and mass treatment (about 43% of all infected persons estimated among whole population) were carried out than other areas (only 20-30%). The proportion of intermediate skin reation (60-100 mm3 wheal size) increased markedly indicating decreased dose of infection which corresponds to the dropped infection rate and average number of metacercaria in crabs. Egg-positive rate in sputum examination done for skin positive reactors also presented similar pattern to skin reaction although it should be taken account that the result of 1964 was from repeated sputum examinations but that of other years from a single examination. Increased proportion of intermediate skin reaction which has much lower egg-positive rate probably played major role in decreased egg-positive rate.

The infection rate of snail started to drop about one year earlier than crab; crab infection rate and intensity started to drop about four year after the mass treatment. The duration needed to show the change of infection status in intermediate hosts after the mass chemotherapy may correspond to the duration of survival of the parasite in the intermediate hosts. With the data available presently, it is difficult to determine on what point of the curve the present status is situated (on decreasing phase or increasing phase?), how far the rate will go down if it is on decreasing phase, and how long would it take in returning to the original status without further management.

The result of follow-up study, however, strongly indicate that continous and intense chemotherapy may be able to put the paragonimiasis under control. Further follow-up study on total population including survey on changes of environment and eating habits is planned.

Tables


Table 1
Population surveyed by village and year


Table 2
Positive rate of intradermal reaction in percent by age group, year, and village


Table 3
Egg-positive rate on sputum examination by village and year for age group of 7-18 years


Table 4
A. Changes of infection status of crab by stream and year

References
1. Yokogawa M, et al. Jpn J Parasit 1961;10(2):317–327.
2. Kim JS. Thesis 1967:68–71.
3. Kim JS. Mass Chemotherapy In The Control Of Paragonimiasis. Korean J Parasitol 1969;7(1):6–14.
 
4. Kim JS. A Comparison Of Sensitivity On Stool And Sputum Examination For Diagnosis Of Paragonimasis. Korean J Parasitol 1970;8(1):22–24.
 
5. Kim JS. A Study On The Infection Status On Intermediate Hosts By Paragonimus On Che Ju Island. Korean J Parasitol 1969;7(3):171–177.
 
6. Kim JS. An Evaluation Of Intraderaml Tests For The Screening Of Paragonimiasis By Comparing Antigens Variously Processed. Korean J Parasitol 1969;7(1):15–24.
 
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