鷄ノ腸寄生虫Heterakis perspicillum生活史ノ研究

Abstract

A few observations as regards life history in some specieses of chicken nematode, especially Heterakis perspicillum, have hitherto been published, though there are a number of reports upon development of Heterakis papillosa.During last three years I have been studying development of parasite, and following results were obtained.In culture experiment with eggs of parasite, Heterakis perspicillum, I have found that it required 7 days to make embryos completely develop within eggs in hottest season of summer, eggs being kept in a shallow layer of physiological salt solution or of 0.2% solution of formalin. At room temperature, however, embryos have never hatched out from ova, if same medium was employed and no mechanical or physical irritation has been given to them.It has been found that egge freshly discharged were still alive, in spite of being exposed to severe coldness out of doors for three months, namely, from January to March, but most of them have been unable to develop to embryonated eggs. The eggs fully developed, which were kept outdoors in frozen water, have also been found vividly alive after a period of four months.In order to determine resistance of eggs against dryness I have kept some eggs not fully developed in a desiccator and found that, after a course of 44 days, they were not capable of being developed to a state in which they could infect, and that ripe eggs containing larvae were still alive after a period of 60 days.The eggs exposed to a temperature ranging from 50°C to 53°C for five minutes, which were have been found still alive, but at 54°C they were found quite dead. The undeveloped eggs whieh were kept in a culture media free from oxygen and those kept in pitch darkness were not able to develop and died within a few days.As is known, shell of Heterakis egg is thick and have a strong resistance thus providing a marked protection against various chemical aubstances. I have made some experiments with regard to resistance of shell, and fonnd that it conld not be destroyed in a few hours by action of ordinary disinfectants. Of all disinfectants which I employed for this purpose, lysol and crude cresol were found to be most destructive, for eggs kept in 0.1% solution of these antiparasitic agents could not survive for a period of 3 days.It is worthy of note that Heterakis perspicillum needs not any intermediate host during its development. Studies on a series of artificially infested chickens killed at short intervals showed that a number of eggs of this worm hatched out in glandular stomach and rest of them in muscular stomach, and moreover that hatched embryos increaesd considerably in size in small intestine. It appeared to me also that larvae required 37 days as minimum period to reach their maturity in alimentary tract of host.I have made some feeding experiments by giving per os eggs of Heterakis perspicillum to chickens, and have shown that no larva was to be found in lungs, liver, kidney and thoracic or abdominal cavity. It may be considered from this fact that there is no evidence of any migration of larvae within body of host during their development such as case of Ascaris larvae. On basis of this experiment it can be said that development of this worm is very simple and direct. This sort of development is one of developing ways of Heterakis perspicillum, and I will call this the Ist developing way.In another series of feeding experiments, it has been found that some of early-stage larvae which reached small intestine penetrated mucosa of domicile through Liverkuehn's glands, and 9-12 days after feeding larva was found in circular muscular layer of intestinal wall.