PITA Fiscal Year 2008 Projects - Environmental Technologies

Genotyping And Phylogenetic Analysis Of Cryptosporidium Spp. Oocysts In The Wissahickon Creek Watershed

Cryptosporidium spp. cause an acute gastrointestinal disease that is self-limiting in otherwise healthy adults but prolonged and life-threatening for the immunocompromised. Cryptosporidium spp. oocysts are a challenge to drinking water treatment plants because (i) they are extremely hardy and resistant to chlorine disinfection and (ii) they are too small (4-8 um diameter) to be effectively filtered. Given these challenges, watershed management to prevent source water contamination is a practical and necessary approach to preventing waterborne cryptosporidiosis.

Cryptosporidium spp. oocysts have been detected in the Wissahickon Creek watershed in southeastern PA, and multiple tributaries to Wissahickon Creek are on the PA 303(d) list due to pathogen impairments. Wissahickon Creek is a major tributary to the Schuylkill River, draining about 64 square miles of lower Montgomery and northwest Philadelphia counties before emptying into the Schuylkill River just upstream of the Philadelphia Water Department's (PWD) Queen Lane Water Treatment Plant (WTP) intake. The proposed work involves the continuation of a long-term watershed monitoring program that will (1) investigate correlations of oocyst presence in the Wissahickon Creek watershed with time of year, weather conditions, and water quality, (2) determine if these correlations hold true from one year to the next, (3) enumerate oocysts of C. parvum and C. hominis, the Cryptosporidium species most linked to human disease, in each sample, (4) determine the ratio of live:dead C. parvum and C. hominis oocysts in each sample, (5) build a library of local genotypes present in the Wissahickon Creek watershed, and (6) identify the likely sources and public health threat of Cryptosporidium oocysts in the watershed using phylogenetic analysis of the 18S rRNA gene. Results will be important for the City of Philadelphia to identify appropriate watershed management strategies to minimize the potential for outbreaks of cryptosporidiosis through the public drinking water supply.