Acute schistosomiasis japonica has become a rare disease in the past fifteen years in Kofu basin because of the marked decrease of
Oncomelania nosophora, however, our attention is drawn to the chronic type of disease which has many clinical problems.
The purpose of this study is to clarify epidemiological status of schistosomiasis at present by means of rectal biopsy, the threshold value of the skin test and COP test.
In the period from 1967 to 1973, the 217 patients of Koma-Kyoritsu Hospital were examined by rectal biopsy, the skin test with Melcher's antigen and COP test under the suspicion of chronic schis-tosomiasis. For determining the threshold value of the skin test, twofold dilution series of the antigen solution were prepared, and microscopic examination was made on the raw specimen obtained by rectal biopsy to see whether the eggs were fresh or old.
The results were as follows :
1) The egg positivity of rectal biopsy specimen was significantly higher than that of stool specimen tested with MIFC method.
2) The COP positivity increased in parallel to the increase of the threshold value of the skin test indiluting grade. Among the patients of rectal biopsy, the COP positivity seemed to be higher in the case with 100 or more eggs. It was also significantly higher in the case being detected fresh eggs in the mucosal specimen.
3) The area irrigated by the River Kamanashi was divided into three districts, I, II and III, according to the collected numbers of the snails, which increased in number in order of I < II < III.
a. The incidence of cases with low dilution threshold value of the skin test decreased in order of I = II > III, while cases with high dilution threshold value increased in order of I< II< III.
b. The incidence of the egg-positive cases by rectal biopsy increased in order of I< II< III.
c. The incidence of the patients with eggs over 100 by rectal biopsy increased in order of I < II <III.
d. The incidence of the patients with only old eggs by rectal biopsy decreased in order of I > II > III, while that of the patients being detected fresh eggs increased in order of I< II < III. Thus, results of rectal biopsy and the threshold value of the skin test corresponded with the distribution of the snails both quantitatively and qualitatively.
As mentioned above, the rectal biopsy and the threshold value of the skin test are the important diagnostic parameters, and they are also important for epidemiological analysis of chronic schistosomiasis in such a situation of infection in Japan, where the eggs in feces used to be discovered with difficulty.
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