自然界に於ける蛔虫卵の分布及び発育・生存期間に関する実験的研究
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概要
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The author has undertaken a close investigation of the distribution, development and longevity of ascaris ova in natural environment. The present study will contribute much towards working out measures to cope with the ascaris infection, clarifying the effects of the elements on the development of ascaris ova. The results revealed by the investigation are summarized as follows: 1) Examinations of the top soil of vegetable fields, dusts on the floor of parasite worms laboratories, dusts on tatami (straw mats), dusts on window sills and sandy dusts in a station waiting room disclosed, after 30-50 times of test in each instances, the presence of ascaris ova at the rate of 50%, 43%, 17%, 46-0x1.f7060bfff5bbp+0nd 4%, respectively. The rate of presence of fertilized ova was (pretty high. Examinations of 50 flies, however, revealed no ascaris ova. 2) The ascaris ova scattered on the soil started growing during the period from March to October in the sun, and from May to October in the shade. The periods spent before starting growing were 2-127 days in the former and 3-76 days in the latter; the higher the temperature the shorter became the period. 3) In the sun ova developed into larvae during the period of 138 days between June 1 and October 17, and in the shade during the period of 106 days between June 28 and October 12. It is prerequisite that proper warmth and sufficient humidity should prevail. 4) In the sun the duration of life of ascaris ova was 16-209 days, or 115 days on the average, whereas in the shade it was 77-245 days, or 141.5 days on the average. 5) The ova scattered in the, sun on the soil during the period from April to September developed into larvae before the year was over. (All the ova scattered in July degenerated and perished in 16 days. High temperature as well as low humidity seems to be responsible for it.) Majority of those scattered in the sun after October passed the winter before developing into larvae.Those scattered in the shade during the period from February to September all developed into larvae before the year was over, but those scattered in the shade after October all perished without developing into larvae. 6) It has been evidenced by indoor experiments that highly dry air helps expedite the death of ascaris ova. It has also been found that the ova kept in highly dry condition reach the morula stage in proper temperature but are prevented from further growth. It seems, therefore, that moisture is indispensable to the growth of ascarisova especially after the morula stage. 7) Exposition of ova to ultraviolet irradiation, when happening repeatedly and for a long duration, interrupted their development. The effect of ultraviolet rays, therefore, is not negligible on the early death of ascaris ova in summer, although it is true that high temperature as well as low humidity is mainly responsible for it. In short, it has been established as the result of the present study that, in natural environment, a temperature of over 20℃ and sufficient humidity are required for the growth of ascaris ova, especially after the morula stage, and, in the absence of both of them, they gradually perish ; that, generally speaking, the duration of life is longer in the shade, and the rise of temperature and dry air due to radiations from the, sun shorten the duration of life ; and that a large amount of ultraviolet rays helps expedite thedeath of ova. Consequently it is recognized that, from the viewpoint of public health, ascaris ova constitute serious problems during the period from June to November and that, of the ova scattered on the soil, those in the shade are epidemiologically more significant than those in the sun.
- 千葉大学の論文
- 1954-07-28