Occurrence of Cryptosporidium and Giardia and the Relationship between Protozoa and Water Quality Indicators in Swimming Pools

Abstract

A total of 60 samples were collected from 35 swimming pools in Beijing, China, and the presence of <i>Cryptosporidium</i> and <i>Giardia</i> were investigated. The results showed that 16.7% and 15.0% of samples were positive for <i>Cryptosporidium</i> oocyst and <i>Giardia</i> cysts, respectively, with a mean concentration of 0.30 oocysts/10 L and 0.27 cysts/10 L. The oocysts and cysts were found to have higher rates of occurrence in August than in May. Genotyping confirmed the presence of <i>Cryptosporidium hominis, C. parvum</i>, and <i>Giardia</i> assemblages A and B, all of which were associated with human infections. The predominant species/assemblages were <i>C. hominis</i> and <i>Giardia</i> assemblage A. Analyses of the relationships between parasite oocysts/cysts, indicator bacteria, and physical-chemical parameters revealed that there was no correlation between 2 parasites and fecal bacterial indicators, whilst there was a significant correlation between protozoa and urea concentration, which indicates that urea concentration rather than fecal bacterial indicators might be an appropriate index for chlorine-resistant protozoa in swimming pools. This study provides useful information to improve the safety of swimming pool water and deduce the risk of protozoan infections.