Cryptosporidium parvum oocysts in zebra mussels (Dreissena polymorpha): evidence from the St. Lawrence River

Molluscan shellfish can recover and concentrate environmentally derived wat erborne pathogens and can be used for the sanitary assessment of water qual ity. Oocysts of Cryptosporidium parvum (genotype 1) were identified in zebr a mussels (Dreissena polymorpha) from the St. Lawrence River, Quebec, Appro ximately 67 oocysts/ml of hemolymph and 129 oocysts/g of soft tissue were r ecovered. The adjusted concentration of oocysts per gram of tissue was 2.2 x 10(2), and approximately 4.4 x 10(2) oocysts were recovered from a single mussel, Zebra mussels can serve as biological indicators of waterborne con tamination with Cryptosporidium.