【摘要】 <正> 大片吸虫(Fasciola gigantica Cobbold,1855)是Cobbold(1855)采自英国马戏团的长颈鹿而描述的。此后巴基斯坦、印度、土耳其、菲律宾、夏威夷和非洲等地区皆有牲畜感染的报导,给当地畜牧业带来严重损失。以往学者描述的安哥片形吸虫变种(F.hepaticavar.angusta Railliet,1895)、埃及片形吸虫变种(F.hepatica var.aegyptiaca Loss,1896)和印度片形吸虫(F.indica Varma,1955)等,目前认为皆是大片吸虫的同种异名(Jackson1927:Sarwar 1957)。更多还原

【Abstract】 The present article reports the larval development of Fasciola gigantica in its snail host under laboratory conditions. The morphology of each stage is described in detail, and also its bionomics studied. Further investigations are made on the epidemiology of fascioliasis of cattle in Tsinchiang region, South Fukien with a view to obtain more precise information on different aspects of the problem.The segmentation of egg was arrested during the cold season of the year and was resumed at the beginning of the spring. At room temperature of 28°-35℃, mass hatching occurred after 10-14 days of incubation. Development of eggs was completely inhibited below 9℃, and at 38℃. The optimum temperature for the development was found to be 25°-30℃, but a temperature of 45°-50℃ was lethal. It was found that none of eggs could withstand drying for more than 10 minutes after exposure to air.The miracidium of Fasciola gigantica is covered with twenty-one ciliary epidermal cells arranged in five transverse rows of 6, 6, 3, 4 and 2 respectively. There are two distinct cells lying at the posterior lateral end of the germ ball which had not been hitherto revealed by former workers. These cells with numerous granules in the cytoplasm are presumably excretory in function.In summer time when the room temperature rises to 26°-34℃, the mature sporocyst with a single redia was recovered in snail host 10 days after exposure to miracidia. The mature mother redia from sporocyst may be obtained from the infected snails dissected 15 days after infection. On 30-32 days after exposure to miracidia, fully developed daughter rediae were found to contain mature cercariae, cercarial embryos and a few germ balls. The arrangements of flame cells and fine tubules in the cercaria and encysted metacercaria were carefully studied. Our observation indicated that there are only 12 pairs of flame cells but not 32 pairs as reported for F. hepatica by Faust (1932). Thus, the formula for the cercaria of F. gigantica can be expressed as 2[(2 + 2 + 2) + (2 + 2 + 2)] = 24.Bcologic factors, such as temperature, light and aquatic medium were found to have effect on the emergence of cercariae. During the cold season of the year at the low temperature of 9°-14℃, the emergence was entirely inhibited. The optimum range of temperature for the emergence was found to be 20°-25℃. Within this range a large number of cercariae escaped from snails in the dark night more likely at hours before dawn, and only few cercariae appeared at the different times of the day. After emergence from snails, the cercariae ascend to near the surface of water. The majority of cercariae eneysted within a distance of 3 cm to the surface. Only few cercariae encysted at various depths.There arc three species of lymnaeid snails, such as Lymnaea (Radix) auricularia, L. (R.) swinhoei and L. (Fossaria) ollida collected in Foochow. Experiments were conducted to study the susceptibility of these snails to infection with the miracidia of Fasciola gigantiea. Results of experiments clearly indicated that only one species, L. (F.) ollida, was highly susceptible (infective rate: 58.95-76.41%) in both young and adult, while the other two species, L. (R.) auricularia and L. (R.) swinhoei can not be experimentally infected with F. gigantiea. L. (F.) ollula which, according to our previous studies (Lin 1956, 1962), also acted as the intermediate host of F. hepatica. The habitat of this snail is semi-aquatic and similar to that of L. truneatula. According to Abbott (1948), this snail has two synonyms, L. pervia and L. philippinensis. L. pervia has been reported to occur widely over the whole China and Japan and acted as the intermediate host of F. hepatica (Shirai 1925). L. philippinensis was recorded as the important vector of both F. hepatica and F. gigantiea in Philippine islands (Jesus 1937).In view of results obtained from previous workers and those of our own, it can be deduced that F. hepatica and F. gigantiea were not clearly seperated by their respective snails as suggested by Kendall (1954, 1959). It更多还原