Prevalence, worm burden and other epidemiological parameters of Ascaris lumbricoides infection in rural communities in Korea
Jong Yil Chai,Koo Soo Kim,Sung Tae Hong,Soon Hyung Lee and Byong Seol Seo
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Seoul 110, Korea.
The epidemiological status of ascariasis was analyzed in 8 rural villages in Korea, through observation of its epidemiological parameters such as prevalence, worm burden and basic reproductive rate. Total 978 inhabitants were subjected to stool examination and recovery of worms after chemotherapy with pyrantel pamoate. The results were as follows: The worm positive rate in each village was 16.5-79.5%, while the egg positive rate was 9-18% lower, 3.3-66.7%. The average worm burden(among all inhabitants) ranged from 0.21 to 8.44 by villages and the frequency of cases with each worm burden showed negative binomial distributions with 'k' values of 0.38-0.54. The prevalence rates (worm) in each village was almost identical with the theoretical ones from Anderson and May's equation; p=1-(1+M(*)/k)**(-k), where 'p' is worm prevalence and 'M(*)' equilibrium average worm burden. The basic reproductive rate 'R' was calculated from 1.03 to 2.11. It is suggested that, although 'R' in lower endemic areas is approaching to the breakpoint of reinfection (R=1), control programs of ascariasis in Korea should be continued until it becomes below the level nationwidely.
Table 1 Studied areas and epidemiological indices for Ascaris lumbricoides infection
Table 2 Distribution of cases by worm burdens in each area
Table 3 Negative binomial* indices for the distribution of individual worm burdens of A. Lumbricoides
Table 4 Theoretical prevalence (worm) and basic reproductive rate (R) according to Anderson et May (1982)'s model
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