An epidemiological study of human paragonimiasis by means of micro-ELISA

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Abstract
As epidemiological parameters of human paragonimiasis, the positive rates of intradermal test and the sputum/stool examination have long been employed in population surveys. However, both the specificity of the intradermal test and the sensitivity of sputum/stool examination have been gradually declined as the endemicity was lowered; thus the gap between above two parameters widened. In such context, the development of a new epidemiological parameter or tool which makes it possible to accurately discriminate the active paragonimiasis cases was necessary. In the present study, the detection rate of Paragonimus-specific IgG antibody by micro-ELISA was evaluated as an indicator of epidemiologic status of human paragonimiasis in a population. A total of 4,285 students and inhabitants living in Bukpyeong Myeon and Bukil Myeon, Haenam Gun, Jeonlanam Do was surveyed in October 1983 by intradermal test first. Out of them, 244 case (5.7 %) were found positively reacted to VBS antigen of P. wetermani. Out of 168 positive reactors, 7 cases (4.2 %) were egg positive either by two times of sputum examination or by one stool examination. That indicated that only 0.16 % of total surveyed were confirmed as active paragonimiasis by egg detection. When sera collected from 239 positive reactors of intradermal test were tested by micro-ELISA for their specific IgG antibody, 40 cases (16.7 %) were found to be positive. All of 7 eggs positive cases were again positive for specific IgG antibody. Among remaining 232 intradermal test positive cases, 33 cases were positive for IgG antibody. In contrast to those, none of 42 positive reactors to intradermal test for Clonorchis and of 128 intradermal test negative cases showed positive for Paragonimus- specific IgG antibody. The rate of specific IgG antibody as detected by micro-ELISA appeared to be increased with the wheal size of the intradermal test. When the wheal size was over 13 mm in diameter, about 50 % of them were positive for specific IgG antibody. Thirty-one specific antibody positive cases were clinically evaluated by laboratory examinations (repeated sputum examination, peripheral eosinophil count and chest roentgenogram) and by history taking. Out of them 24 cases were associated with one or more positive laboratory findings; thus considered as active paragonimiasis cases. Out of 7 lab. finding-free cases 3 revealed past history of typical paragonimiasis symptoms, suggesting that they were in chronic or in convalescent stages. The remaining 4 cases were considered as either mild or ectopic infection cases; the possibility of cross-reaction with other helminthiases could not be ruled out. From the above results, it was inferred that the detection of Paragonimus-specific IgG antibogy by micro-ELISA was very much helpful in detecting the active cases as well as in proper evaluation of the endemicity of human paragonimiasis in a population. The convenience of mass handling of sera in micro-ELISA was considered another superiority as an epidemiologic tool.

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