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시식성(屎食性) 동물의 인체기생충 전파에 관한 연구 : 특히, 회충 및 십이지장충에 관하여

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 (A) study of the role of coprophagous animals in the transmission of human parasites, with special reference to ascaris and hookworm 
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Introduction On the epidemiological point of view, several coprophagous domestic animals and worms are considered having an important role in the transmission of the intestinal parasites in Korea as well as in the other parts of the world. Chandler(1929) reported that domestic animals spread parasite eggs through their body surface or digestive tract and Yoshida(1961) found a few human hookworm larvae which had developed to the adult stage in an abnormal host, dog. However, he failed to check the survival period. Ackert(1922) observed that hookworm eggs taken by the hog passed intact through its intestine of hog, while larvae were passed in a degenerated form. However he did not mention whether some larvae migrated through the wall of the intestine. Schwartz et al.(1934), Sasada (1935), Nichols(1956) and Soh(1958) observed matured ascaris eggs which hatched in the rat intestine, migrated into various tissues, and survived as long as 392 days after the infection. And none of them was checked whether or not the larvae could be passed intact from the intestine. Their studies only traced the migratory route through the tissue. Ackert(1922) presumed that human hookworm larvae would pass intact through the chicken intestine, and Otto et al.(1931) found ascaris and trichuris eggs in chicken feces in Tennessee. Sasada(1937) observed that many of the hog ascaris eggs and a few hookworm larvae passed through a chick intestine without changing form. None of the above studies were concerned with the fresh, matured eggs of ascaris nor the eggs and larvae of hookworm. Miller(1961) reported that Canthon laevis and C. vigilans could destroy the ascaris and hookworm eggs with their mandibular grinding apparatus, but that another species of beetle; Planeus vindex and P. igneus were very weak in their destructive ability. Earthworm is also one of the common coprophagous annelids, but its action on parasite eggs has not been studied. The present study were undertaken to define more precisely the vector effect of coprophagous animals and to supplement the incomplete past information. The aim is to increase the number of communities where no parasitic diseases exist. Methods Fresh eggs of Ascaris lumbricoides and Ancylostoma caninum or A. duodenale, and the infective form of each were given to dogs, pigs, chickens, rats, earthworms, and dung beetles. The fate of the eggs and larvae were traced by examination of various organs or fecal materials. Other associated experiments were done using related method to substantiate the results. Results Ⅰ. Domestic animals as a carrier of human parasites in several rural villages: Fecal specimens from several animals were examined in four rural villages. Two of the villages were in Koyang, Kyonggido and the other two were in Dongnae, Pusan, Human parasite eggs were found in 13 out of 78 chickens, 4 out of 25 rats, 11 out of 60 dogs and 11 out of 60 hogs. The fecal excretions of 462 earthworm which were collected under natural conditions showed human parasite eggs. Ⅱ. Fate of human ascaris and hookworm eggs and larvae of human hookworm which were ingested by several fowls and animals; 1. Chicken. Most of the hookworm eggs and immature ascaris eggs were discharged within a day and cultivation confirmed that the eggs were alive. Hookworm larvae of the filariform were not found in stool, but rather they migrated to the lung, liver and muscle. The matured ascaris eggs hatched in the intestine and also migrated into several organs. Some were discharged in very inactive condition. 2. Dog. Both the fresh eggs of hookworm and ascaris passed without change, although larvae were found in various organs after the ingestion of hookworm larvae or matured ascaris eggs. A very few filariform larvae of human hookworm among ingested by the dog developed to an adult stage and produced eggs for a few months. 3. Hog. Hookworm eggs were discharged without changing form and survived as long as one week in a pig-sty medium. Hookworm larvae eaten by pigs migrated into organs and tissues, and could not detect in its stool. Fresh ascaris eggs were discharged in living condition and 56% survived in a pig-sty medium as long as 30 days. The number of discharged matured ascaris eggs and their migration was cut almost in half. 4. Rat. Orally administered hookworm eggs and ascaris fresh stage eggs were discharged without change in form, while the hookworm larvae were not discharged in a living form, though a few larvae from mouse feces passed alive. The larvae which were collected from the lung could infect another mouse, when given percutaneously. Many of the matured ascaris eggs were discharged, but some migrated into various organs. Ⅲ. Studies on the fate of ascaris and hookworm eggs and larvae eaten by coprophagous annelids and scarabeid insects. 1. Earthworm. Human parasite eggs were found in 9 of 462 earthworms which were caught in the dooryard in rural villages. The common species of Annelids: Lumbricus terrestis was selected for study. Eggs of ascaris and hookworm which were ingested with soil passed without change through the digestive tract. The rhabditoid larvae in the intestine developed to the filariform stage and were passed out or migrated into a body cavity and some of them returned to the intestinal lumen. 2. Dung Beetle. Of 66 beetls caught from the field, a liver fluke egg was found from one case. The common dung beetles in Korea. Copris ochus and Onthophagus lenzii, were experimentally fed with human feces containg ascaris eggs and also a medium containing hookworm larvae. It was found that none of the eggs and larvae were injured, even though these beetles had a fine mandibular cutting apparatus. Conclusion Through the above findings, it is shown that coprophagous domestic animals have an important role in spreading the fresh eggs of ascaris and hookworm, and that stools eaten by domestic animals has very little effect on the spread of the infective form of ascaris or hookworm. However, coprophagous annelids and scarabeid beetles can spread eggs and larvae, regardless the developmental stage form of the parasite without damage to either.
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