Molecular identification and distribution of Cryptosporidium and Giardia duodenalis in raw urban wastewater in Harbin, China.

Contamination of the water supply by protozoa often causes outbreaks of cryptosporidiosis and giardiasis. The goals of the present study was to investigate the level of Cryptosporidium and Giardia duodenalis in wastewater from wastewater treatment plants in Harbin, China, and to understand the endemic transmission characteristics of cryptosporidiosis and giardiasis. Forty-eight domestic wastewater specimens from the two wastewater treatment plants in Harbin City were collected from April 2009 to March 2010. Cryptosporidium spp. and G. duodenalis assemblages were identified by PCR and sequencing of the 18S ribosomal RNA and the triosephosphate isomerase genes, respectively. In total, 15 wastewater specimens were PCR positive for Cryptosporidium and 23 were PCR positive for G. duodenalis. The prevalence of contamination with G. duodenalis (47.9%) was higher than that of Cryptosporidium (31.3%). Molecular identification showed the presence of two Cryptosporidium spp. (14 belonging to Cryptosporidium andersoni and one belonging to Cryptosporidium ubiquitum) and two G. duodenalis assemblages (18 belonging to assemblage AII and six belonging to assemblage B). In addition, eight specimens contained both Cryptosporidium and G. duodenalis, and one specimen contained G. duodenalis assemblages AII and B. These results suggested humans might be the primary source of G. duodenalis contamination in wastewater in the studied area. In contrast, a low prevalence of C. ubiquitum suggested a reduced risk of human cryptosporidiosis caused by C. ubiquitum via waterborne route. This work provides basic experimental data needed for local wastewater treatment plants to develop protective strategies for water safety and to eliminate waterborne parasites.