Comparison of the migrations of Fasciola hepatica sporocysts in Lymnaea truncatula and other related snail families.

The migration and definitive localization of sporocysts in the snail body were studied in four species (Aplexa hypnorum, Lymnaea glabra, L. truncatula, Physa acuta), each of which was exposed to a single miracidium and killed during a period ranging from the 1st to the 5th day postexposure. When penetration occurred through the mantle, tunnels were found mainly in the mantle or kidney in Lymnaea adults and also extended to the foot in many physidid adults and in newborns of the four species. The sporocysts preferentially localized in the zone surrounding the kidney and heart beginning on the 4th day in Lymnaea spp. and disappeared in Aplexa and Physa snails on the 3rd day. When penetration occurred through the foot and extended inconstantly to the mantle according to the snail species involved. Sporocysts were encountered in the foot as well as the mantle or the zone surrounding the kidney and heart. The significance of these results is discussed in relation to the snail host and the entry site used by the Fasciola hepatica miracidium.