Viability and infectivity of oocysts recovered from clams, Ruditapes philippinarum , experimentally contaminated with Cryptosporidium parvum

Abstract

This study confirms the important role of marine bivalve molluscs, destined for human consumption, as transmitters of cryptosporidiosis, zoonotic diarrhoeal disease caused by Cryptosporidium parvum. C. parvum oocysts recovered from seawater clams (Ruditapes philippinarum) were viable and infective in five of eight infected neonatal CD-1 Swiss mice. Oocysts were observed in clam gill and gastrointestinal tract tissue homogenates as well as in gill histological sections, by an immunofluorescent antibody technique. In vitro viability of recovered oocysts was also determined using fluorogenic vital dyes (75% viability).

Molecular Epizootiology of Toxoplasma gondii and Cryptosporidium parvum in the Eastern Oyster (Crassostrea virginica) from Maine (USA)

“…Experiments conducted in aquaria indicate that T. gondii and C. parvum oocysts can be retained in the bivalve for long periods in the gastrointestinal tract, gills, hemolymph, and intervalvular liquid [38,39,40,41,42,43,44]. It has been reported that C. parvum recovered from environmental samples retain viability [45], and although salinity affects the viability of C. parvum oocyst, they remain active for up to four weeks in estuarine conditions [33]. An approximation of the parasite load of wild mussels collected in C. parvum positive sites indicated that each shellfish transports between 6 and 1000 oocysts [46,47].…”