Occurrence of Cryptosporidium oocysts in sewage effluents and correlation with microbial, chemical and physical water variables

Contaminated water are recognized as a potential source of Cryptosporidium oocysts. In Italy studies on the environmental spread of the parasite are still scarce even if a high frequency of serological responses could suggest high rates of endemic Cryptosporidium infections. In this investigation the occurrence of the parasite in water samples from a municipal wastewater treatment plant was monitored with the aim to evaluate possible correlation between oocysts and bacterial indicators, pathogens and physico-chemical parameters using a multivariate analysis. Data collected showed high numbers of oocysts, with a high percentage of positive samples and a significant correlation with pH, redox potential and total organic carbon. No correlation was found between Cryptosporidium concentration and that of the other microrganisms. The results, through a probing statistical analysis, show that none of the selected microrganisms was a reliable predictor of the presence of the parasite.