Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 27. (Budapest, 1994)

magna in Europe (Erhardová-Kotrlá 1968). In America, several water-snail species belonging to the Lymnaea s. sir. subgenus have been demonstrated to act as potential intermediate hosts for the large liver fluke of deer (Griffiths 1955,1959,1973, Malek 1980). The European representatives of this group of species are indigenous also in Hungary, and they are especially common in the Szigetköz and along the River Danube (Pintér and Szigethy 1979). Therefore, it can by no means be excluded that, besides Lymnaea truncatula, occasionally also other Lymnaea spp. occurring in Hungary may serve as a subject for the helminth's parthenogenetic development. Depending on the ambient temperature, the developmental stages of F. magna can persist in these snails for some months or even for a half year. In frost-free places the metacercariae of F magna may overwinter and may remain viable for as long as a year (Griffiths and Christensen 1972, 1974). After even a single successful infection, infected deer will shed fluke eggs from the fluke-containing cysts through the biliary ducts practically throughout the remainder of their life (Foreyt et al. 1977). Although the fertility of eggs produced by old flukes decreases (Erhardová-Kotrlá 1968), due to the helminths' high egg-producing capacity the deer, even those infected on a single occasion, can always shed viable eggs. From all this a slow spread of F magna infection in the Danube valley can be anticipated. Because of its proximity, the big game population of the Hanság area is also at risk; in addition, through artificial transfers of big game the fluke may be carried to other regions of Hungary as well. Both roe-deer and deer are definitive hosts of the large American liver fluke; shedding viable fluke eggs, they may spread the infection throughout their entire range of occurrence (Kotrly and Kotrlá 1980). The wild boar (Sus scrofa) and naturally also the domestic pig act as paratenic hosts of the fluke. Although these species not shed fluke eggs (Foreyt et al. 1975), F. magna causes severe liver lesions. In Hungary, the fallow deer (Dama dama) originally considered an exotic species, is also at risk oîF. magna infection, as it is highly susceptible to that fluke (Erhardová-Kotrlá and Blazek 1970, Pfeiffer 1982). The rich animal population of game preserves and deer forests, comprising a multitude of antlered species, provides an ideal medium for the proliferation of infection (Kotrlá and Kotrly 1977). All things considered, large American liver fluke infestation is usually not fatal to game living in the forest; however, this fact also means that the conditions necessary for parasite persistence are available in that environment. The other reason why the large American liver fluke is important, is its role in infecting domestic animals. The fluke, developing within a closed cyst, produces chronic liver lesions in cattle (Price 1953). In this host the maturation process and egg laying may occur even 20 weeks after inoculation (Foreyt 1988), but the eggs can leave the liver only in case of very severe infections because of the closed cyst. Therefore, cattle do not regularly shed F magna eggs but sustain more damage through that infection than cervids. (In the fourth edition of their basic parasitological book, Boch and Supperer (1992) stated that the patent period of this fluke in cattle might last as long as five years; however, we could not find any original papers or published data about this phenomenon.) Sheep and goats invariably succumb to F magna infection