Clams (Dosinia exoleta, Ruditapes philippinarum, Venerupis pullastra, Venerupis rhomboideus, Venus verrucosa), mussels (Mytilus galloprovincialis), and oysters (Ostrea edulis) were tested for the presence of Cryptosporidium sp. oocysts using various stain techniques and a commercially available kit containing fluorescein isothiocyanate-conjugated monoclonal antibodies. All molluscs were harvested in northwest Spain (Galicia) except for R. philippinarum, which was from Italy, and 1 of the 6 oyster samples, which was from England. The results showed the presence of Cryptosporidium sp. oocysts in all of the molluscan species destined for human consumption.
Samples of two species of shellfish that form part of the human food chain (the oyster Ostrea edulis and the marine clam Tapes decussatus) were experimentally contaminated with Cryptosporidium parvum oocysts. Changes in the viability of oocysts subsequently recovered from the shellfish were evaluated by means of an immunofluorescent antibody technique (IFAT) and inclusion/exclusion of the fluorogenic vital dye propidium iodide. There was a sharp decrease in oocyst viability during the first 4 days, with 15-25% viable oocysts remaining thereafter. In addition the infectivity of these oocysts at 10 and 31 days post-contamination was demonstrated using a suckling murine model.
Single faecal and serum samples were individually collected from 135 asymptomatic adult cows on seven farms in Cundinamarca (Colombian Andean region). Tests for the presence of oocysts of Cryptosporidium parvum (carbol fuchsin stain) and Eimeria spp (flotation in saturated saline solution) revealed that none of the animals had coccidia in their faeces. The IgG antibody levels to C. parvum were measured by an enzyme-linked immunosorbent assay (ELISA) technique and the reactivity to C. parvum antigens by a Western blotting procedure. Cryptosporidial antibodies were detected in cattle from all farms, with 53.3% (72 animals) being seropositive. Sera recognized 5-11 protein fractions with molecular masses ranging from 12 14 kDa to 97-100 kDa. Sera considered as positive by ELISA reacted intensely and more frequently with protein fractions of approximately 20-22, 42-48, 51-57 and 60-69 kDa, whereas only the 42-48 kDa antigen was strongly recognized by sera without IgG antibodies. The presence of IgG antibody against C. parvum in most animals, as well as the reactivity to major proteins of C. parvum, could be indicative of continuous exposure to this parasite.
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