Dr. Murai Éva szerk.: Parasitologia Hungarica 18. (Budapest, 1985)
Parasit, hung. 18. 1985 Infectivity of metacercariae of Fasciolopsis buksi (Lankester, 1857) and their development in definitive host Dr. Le NGUYEN THI — Dr. Ottó SEY Institute of Biology, National Scientific Research Centre, Hanoi, Viet Nam — Department of Zoology, Janus Pannonius University, Pécs, Hungary "Infectivity of metacercariae of Fasciolopsis buski (Lankester, 18 57) and their development in definitive host" - Nguyen Thi, Le - Sey, O. - Parasit, hung. , 18: 11-15. 1985. ABSTRACT. Metacercariae of Fasciolopsis buski have survived under favourable natural conditions up to two months. The prépaient period is about fifty days while the body size of the worms is on an average 10.0 by 3.9 cm. The highest egg production was observed between 50-258 days post infection and discharging of eggs has continued up to eight and a half months after infection. KEY WORDS. Fasciolopsis buski, metacercariae, infectivity, definitive host, Trematoda Fasciolopsis buski , the giant intestinal fluke, is a parasite of man and hog in several Southern and South-East Asian countries, including Viet Nam. While considerable attention has been paid to fasciolopsiasis of man in the endemic areas, fasciolopsiasis of pig has been the object of only a few studies. According to present knowledge the causative agent of human and animal fasciolopsiasis, is the same strain of F. buski, thus pigs, as reservoire hosts, play an important role in the maintenance of fasciolopsiasis in rural communities. On the other hand, heavy worm burden in pigs can cause important economic losses therefore studies aiming at better understanding of ecological aspects of fasciolopsiasis are contributions to the knowledge of epidemiology and to the strategy of prevention and control of this disease. MATERIAL AND METHODS Metacercariae were collected from naturally infedted snails, Segn^entina_ hçniisghaerula found in the vicinity of pig farms. They were stored at room temperature and used for infestion at various intervals. Twenty pigs, kept in worm-free conditions (experimental station, Vietnamese Research Center) were infected with metacercariae of different ages (Table 1) and pigs were sacrified in three months post infection. The flukes were counted, and stained with carmine by the usual method. RESULTS AND DISCUSSION The experimental data presented in Table 1 show that metacercariae survive under favourable natural conditions (on the lower surface of submerged aquatic plants) up to two months or even longer. Just after encystment, metacercariae are ready to grow into fluke but the longer the time elapsed after encystment, the lesser their infectivity: in the first days 45. 1% and in 60 days 5. 6%. The highest survival rate is in the first two or three weeks (45. 126.8%).
