Interference of Echinoparyphium elegans with the host-parasite system Bulinus truncatus-Schistosoma bovis in natural conditions.

Histological observations of Bulinus truncatus naturally infected by both Schistosoma bovis and Echinoparyphium elegans in Sardinia (Italy) have shown that E. elegans is pathogenic to the mollusc and dominant to the schistosome. The larval stages, rediae and metacercariae, acted as compressors. Rediae, mainly the young and very motile ones, also behaved as predators. The organs of the mollusc were variably affected; the ovotestis totally disappeared. The larval development of the schistosome was disturbed; cercariogenesis was strongly inhibited and gave way to high sporocystogenesis. The intensity of this interference depended on the density of echinostome larvae present.