Detection of Giardia genotypes in sewage and in stool samples in Israel

Giardia is a protozoan parasite which causes a severe disease called Giardiasis. This study was conducted to determine the prevalence of Giardia cysts in raw wastewater and its prevalence in the study community. Furthermore, the prevalence of assemblages A and B in sewage was compared with their prevalence in stool samples tested positive for Giardia. All wastewater samples were found positive for Giardia at a concentration range of 10-12225 cysts/L. Positive stool samples contained Giardia at an average concentration of 1.4x105cysts/gr. Giardia assemblage A alone was detected in 38.2% of wastewater samples, whereas assemblage B was not detected separately. However, 61.8% of the samples were found to contain both assemblages. In stool samples, the majority 27 out of 50 (54%) were found to contain assemblage B, 34.6% contained assemblage A and only 11.5% contained a mix of both assemblages. The results of the study indicate that Giardia is highly prevalent in wastewater in Israel reflecting its prevalence in the community. In addition, assemblage A is highly prevalent in wastewater, whereas assemblage B is more prevalent in stool samples, suggesting milder and/or carrier state of infection for assemblage A.