Pathogenic Parasite Accumulation in Environmental Biofilms in an Endemic Location

Introduction: Aquatic biofilms trap waterborne protozoan parasites, some of these parasites cause significant disease in humans. These parasites can be released from the biofilm and cause contamination in subsequent water usage. Cryptosporidium, Giardia, and Cyclospora are considered among the main protozoan parasites of concern for food production.

Purpose: The purpose of this study was to locate sources within biofilms of protozoan parasites in water used for agriculture.

Methods: Biofilms were collected from agricultural water surfaces in an endemic area for Cyclospora cayetanensis and analyzed for the presence of protozoan parasites. Cryptosporidium and Cyclospora were detected using nested PCR-RFLP using the 18S ribosomal RNA as a target gene. Cyclospora was also observed using light and epifluorescence microscopy. Cryptosporidium and Giardia were detected using immunofluorescence tools (IFA).

Results: Analysis of 64 samples collected in an endemic area during the low season period using nested PCR (nPCR) for Cyclospora resulted in 23 presumptive Cyclospora-positive samples. By RFLP one was confirmed positive. Two samples were positive for Cryptosporidium sp. by nPCR and four by IFA. Giardia sp. was identified in 24 samples by IFA. 

Significance: This study demonstrates that biofilms on surface water used for agricultural purposes can serve as a reservoir for protozoan parasites and could be a potential source for foodborne parasitic infections.