Detection of infectious Cryptosporidium parvum oocysts in mussels (Mytilusgalloprovincialis) and cockles (Cerastoderma edule)

Infective Cryptosporidium parvum oocysts were detected in mussels (Mytilus galloprovincialis) and cockles (Cerastoderma edule) from a shellfish-produc ing region (Gallaecia, northwest Spain, bounded by the Atlantic Ocean) that accounts for the majority of European shellfish production. Shellfish were collected from bay sites with different degrees of organic pollution. Shel lfish harboring C, parvum oocysts were recovered only from areas located ne ar the mouths of rivers with a high density of grazing ruminants on their b anks. An approximation of the parasite load of shellfish collected in posit ive sites indicated that each shellfish transported more than 10(3) oocysts . Recovered oocysts were infectious for neonatal mice, and PCR-restriction fragment length polymorphism analysis demonstrated a profile similar to tha t described for genotype C or 2 of the parasite. These results demonstrate that mussels and cockles could act as a reservoir of C. parvum infection fo r humans. Moreover, estuarine shellfish could be used as an indicator of ri ver water contamination.