The ability of eight species of freshwater snails to sustain the larval development of Paramphistomum daubneyi Dinnik, either singly or in combination with Fasciola hepatica Linne.

Eight species of freshwater snails, originating from the Haute-Vienne, Indr e, or Puy-de-Dome departments (central France), were subjected to experimen tal infections with Paramphistomum daubneyi (5 miracidia per snail) to dete rmine whether they might act as intermediate hosts in the trematode life cy cle. Juvenile (1-1.5 mm high) and preadult (3-4 mm high) snails did not sus tain the full larval development of P. daubneyi. However, live larval forms were found in some juvenile Aplexa hypnorum (sporocysts), and in juvenile Lymnaea fuscus, L. palustris, and L. stagnalis (sporocysts and immature red iae). No infections were noted in Lymnaea ovata, L. peregra, Physa acuta, a nd Planorbis spirorbis. Preadults of the 4 former species were also subject ed to double infections with P. daubneyi and Fasciola hepatica (1 miracidiu m of Fl daubneyi + 1 miracidium of F. hepatica 4 hr later for each snail). Cercariae of P. daubneyi were released from L. fuscus (1,6 %) and L. palust ris (1,2 %). Post-mortem dissection of snails demonstrated the presence of some P. daubneyi sporocysts and immature rediae in both aforementioned spec ies, and the absence of larval forms in A, hypnorum and L,. stagnalis. No l arval forms of F: hepatica were found in these snails. Some freshwater snai ls may thus harbour an immature or mature P. daubneyi infection and this ab ility varied in relation to the snail species and population studied. This variability may be explained by varying frequency of encounter between para site and snail in the field.