Identification of and subtype ST3 in Cholga mussel and treated sewage: Preliminary evidence of fecal contamination in harvesting area.

and are foodborne parasites known for causing diarrhea. They accumulate in mussels grown on contaminated water bodies, due to the discharge of treated sewage from sewage treatment plants (STP). Despite this, some countries like Chile do not include these parasites in the control or monitoring of sewage water. The objective of this research was to evaluate the contamination of . and from treated sewage (disinfected by chlorination) and Cholga mussels in a touristic rural cove from the bay of Concepción. Cholga mussels from commercial stores and a treated sewage sample were analyzed. spp. was identified by Ziehl-Neelsen-Staining (ZNS) and by direct-immunofluorescence assay (IFA) from ZNS-positive samples. was identified by PCR using locus SSU rDNA. and subtype ST3 were found in 40% and 45% of Cholga mussel samples, respectively, and both parasites were identified in the treated sewage. SSU rDNA gene alignment from Cholga mussels and treated sewage showed 89% of similarity, indicating that could be the same parasite in both samples. We describe the first evidence of possible contamination with these parasites from treated sewage to Cholga mussel suggesting an environmental contamination with high human risk. Based on these results, further studies will consider all the rural coves and STP from the bay to prevent possible contamination of these parasites.