Cryptosporidium genotype and subtype distribution in raw wastewater in Shanghai, China: evidence for possible unique Cryptosporidium hominis transmission

Abstract

To identify the genotype and subtype distributions of Cryptosporidium oocysts in domestic wastewater in Shanghai, China, and to facilitate the characterization of the endemic transmission of cryptosporidiosis, raw domestic wastewater samples were collected from four wastewater treatment plants in Shanghai, China, from December 2006 to April 2007. Genotypes of Cryptosporidium species were detected based on PCR-restriction fragment length polymorphism and sequence analyses of the small-subunit rRNA gene. Samples that contained Cryptosporidium hominis were further subtyped by DNA sequencing of the 60-kDa glycoprotein gene. Among a total of 90 samples analyzed, 63 were PCR positive, 10 of which had mixed genotypes. Fifty-nine (93.7%) of the PCR-positive samples had C. hominis, and 7 (11.1%) had C. meleagridis. The other seven Cryptosporidium species/genotypes identified included C. baileyi, C. parvum, C. suis, C. muris, rat genotype, avian genotype III, and a novel genotype. Forty-seven of the 59 C. hominis-positive samples were successfully subtyped, with 29 having subtype family Ib and the remaining belonging to subtype families Ia, Id, Ie, and If. The three Ib subtypes identified, IbA19G2, IbA20G2, and IbA21G2, were very different from the two common Ib subtypes (IbA9G3 and IbA10G2) found in other areas of the world. Likewise, the Ie subtype IeA12G3T3 was also different from the common IeA11G3T3 subtype. Thus, the presence of multiple subtype families and unique Ib, Ie, and If subtypes indicates that there might be endemic transmission of cryptosporidiosis in the study area and that C. hominis populations there might be very different from those in other areas.