Parasite development and visceral pathology inGalba truncatulaco-infected withFasciola hepaticaandParamphistomum daubneyi

Abstract

AbstractHistological investigations inGalba truncatulanaturally or experimentally co-infected withFasciola hepaticaandParamphistomum daubneyiwere carried out to study parasite development and the responses of the digestive gland and kidney of snails, as larval forms of these digeneans often use these two sites for their growth within the snail's body. The number of live rediae per snail ranged from 2.4 to 4.2 for the dominating parasite (it developed in the digestive gland) and was less than 2.0 for the other species. When the dominating species wasF. hepatica, most snails harboured cercariae-containing rediae; if this parasite wasP. daubneyi, procercariae-containing rediae with or without free procercariae were observed in most snails. In contrast, most rediae of the other species were immature. The pathology caused by the dominating species in the digestive gland was greater than that recorded in the kidney, where the other parasite was generally located. The most frequent tissue lesions in the digestive gland were generalized epithelial necrosis and epithelial reconstitution. In the kidney, multifocal epithelial necrosis was frequently observed, particularly whenP. daubneyiwas the dominating species. The frequencies of lesions in the digestive gland agreed with percentages reported by our team in other snails mono-infected withF. hepaticaorP. daubneyi. In contrast, multifocal necrosis in the kidney was clearly greater in the present study and this finding might be explained by assuming that a sufficient number of free larvae within the snail would be necessary for the development of epithelial necrosis in the whole kidney.