Q-221. A Multi-Year Cryptosporidium Source Tracking Study in the Wissahickon Creek Watershed

K. L. Jellison, A. E. Lynch, J. M. Ziemann;
Lehigh Univ., Bethlehem, PA.

The research objective was to identify the sources of Cryptosporidium oocysts in Wissahickon Creek, a drinking water source for the city of Philadelphia. Cryptosporidium is spread via fecal-oral transmission and is responsible for a gastrointestinal disease that can be severe and life-threatening for immunocompromised people. Identification of oocyst sources in Wissahickon Creek will help the Philadelphia Water Department implement appropriate watershed management to minimize the public’s exposure to waterborne Cryptosporidium. Two surface water samples in Wissahickon Creek (Wiss 140 and Wiss 410) and three wastewater treatment plant (WWTP) effluents that discharge into Wissahickon Creek (Abington, Ambler, and Upper Gwynedd) were sampled biweekly for 3 years. An additional sample during wet weather was collected each month whenever possible. All water samples were filtered with Envirochek HV filter capsules. In addition, fecal samples from wildlife and domesticated animals within the watershed were collected each month. Oocysts were purified from filter pellets and fecal samples by immunomagnetic separation, DNA was extracted from purified oocysts, and nested PCR targeting the hypervariable region of the 18S rRNA gene was performed. PCR amplicons were cloned, sequenced, and analyzed by phylogenetic analysis. Cryptosporidium was detected in approximately 20% of surface water samples in each of the three years of the study; the genotypes detected suggest that human and wildlife inputs are dominant in the watershed. Cryptosporidium was detected in 8% of watershed fecal samples; data suggest that wildlife, particularly deer and geese, may serve as important reservoirs of infectious Cryptosporidium in the watershed. Cryptosporidium genotypes recovered from the WWTP effluents were closely related to genotypes detected in surface water samples, indicating that WWTP effluents are a source of oocysts in Wissahickon Creek as well. No clear seasonal trend of oocyst detection in the watershed, and no seasonal trend associated specifically with oocyst genotypes, was observed.