Molecular forensic profiling of Cryptosporidium spp. to determine the diversity of fecalcontamination in four Canadian watersheds

摘要

Livestock, humans and wildlife are generally believed to be major contributors ofCryptosporidium contamination in surface waters in Canada. Cryptosporidium is a relativelystrict host-specific parasite, and molecular typing of Cryptosporidium is emerging as aneffective fecal source tracking tool. The Cryptosporidium species/genotypes commonlyidentified in water can yield insights into the nature of anthropogenic inputs (i.e., human oranimal waste) and thus help inform source water protection strategies. Detection ofCryptosporidium forms harboured by the dominant livestock species within a watershedshould be evidence for agricultural contamination. To challenge this hypothesis, parasiteoccurrence and molecular profiling were used to track fecal contamination in watershedsheavily dominated by swine production (the Bras d’Henri/Fourchette watershed, QC), beef ordairy cattle (Oldman watershed, AB; South Nation watershed, ON), and intensive poultryfarming (the Sumas watershed, BC). Parasites were monitored on a bi-weekly basis from thespring to the fall of 2006 using USEPA Method 1623. Levels of Cryptosporidiumcontamination ranged widely through the sampling period with average watershed valuespeaking at 0.77 oocysts/litre for the Bras d’Henri/Fourchette watershed; 0.86 oocysts/litre forthe South Nation watershed; 0.36 oocysts/litre for the Oldman watershed; and 0.21oocysts/litre for the Sumas watershed. Molecular forensic profiling of Cryptosporidiumpositive microscope slides at high occurrence levels from these watersheds resulted in 4species/genotypes from the Bras d’Henri/Fourchette watersheds (C. andersoni, muskrat IIgenotype, W7 genotype and W15 genotype); 6 from the Oldman (C. andersoni, C. baileyi,cervine genotype, muskrat II genotype, skunk genotype and W15 genotype); 6 from theSouth Nation (C. andersoni, C. parvum, muskrat II genotype, muskrat I genotype, W7genotype and W12 genotype) and 4 species/genotypes from Sumas watershed (C. muris,opossum I genotype, muskrat I genotype, W15 genotype). Wildlife species ofCryptosporidium were commonly found in all four watersheds. Surprisingly, only in thecattle-dominated watersheds (Oldman and South Nation) did Cryptosporidium speciesoccurrence correlate with the dominant livestock species farmed (i.e., a predominance of C.andersoni). In poultry and swine dominated watersheds (Sumas and Bras d’Henri/Fourchettewatersheds, respectively) the diversity of Cryptosporidium observed in the water did notappear to correlate with host-adapted forms associated with the dominant animal agricultureactivity (i.e., C. meleagridis, C. baileyi, C. suis or pig genotype II). These preliminaryfindings did not support the stated hypothesis indicating that genotyping tools are necessaryfor determining the animal hosts responsible for contributing parasites into the watershed.