. Animal parasites and human disease. Parasites; Medical parasitology; Insects as carriers of disease. Fig. 76. Egg and ciliated em- bryo of Chinese fluke, Clonorchis sinensis, x 700. (After Katsurada.) Little is known of the life history of any species except the Chinese fluke, C. sinensis. The eggs (Fig. 76A) are of charac- teristic shape, and hatch in water into miracidia (Fig. 76B). The encysted cercarise of this fluke (Fig. 77A) have been found in the subcutaneous tissues and muscles of 12 different species of fresh-water fish. The cysts, which are very small, measuring only about by
. Animal parasites and human disease. Parasites; Medical parasitology; Insects as carriers of disease. Fig. 76. Egg and ciliated em- bryo of Chinese fluke, Clonorchis sinensis, x 700. (After Katsurada.) Little is known of the life history of any species except the Chinese fluke, C. sinensis. The eggs (Fig. 76A) are of charac- teristic shape, and hatch in water into miracidia (Fig. 76B). The encysted cercarise of this fluke (Fig. 77A) have been found in the subcutaneous tissues and muscles of 12 different species of fresh-water fish. The cysts, which are very small, measuring only about by mm. (j^ by 2k of an inch), are usually more abundant in the superfi- cial than in the deeper tissues. Although cysts can be found in fish throughout the year, the younger ones are more frequently met with in late summer and early autumn. When infected fish are eaten, according to experiments re- cently made with animals b}r Kobayashi, the larval flukes escape from the cysts (Fig. 77B) within three hours, and in fifteen hours they may already have reached the bile duct and gall bladder. The parasites reach maturity and eggs are found in the faeces of the host within 26 days. The young flukes have a spiny cuticle until nearly mature, but the spines finally disappear. Muto recently found cer- carise in the snail Bythinia striatula var. japonica which encyst in fish of various species. When these fish are fed to dogs and mice, infection with Clonorchis sinensis results. On the other hand, controls fed with fish parasitized by cercarise from the snail Melania libertina, which Kobayashi believed to be the first intermediate host, developed infections with Meta- gonimus only. Sporocysts develop in Bythinia about three weeks after infection with the miracidia. It is probable that the European liver fluke, O. felineus, and its. Fig. 77. Larvae of Chinese fluke; A, ccrcaria encysted in fish; B, larva freed from cyst; m., mouth in oral sucker; v. s., ventral sucker; ox. v., excretor
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1922
