Occurrence of Giardia and Cryptosporidium in effluents of urban wastewater treatment plants: A global systematic review and meta-analysis

Giardia and Cryptosporidium the important causative agents of intestinal parasitic diseases (IPD) are ubiquitously distributed in the environment, especially in wastewater and reclaimed water. Due to the water shortage crisis and extensive utilization of reclaimed water, the presence of these parasitic protozoa in wastewater is a concern from the public and environmental health point of view. To address this concern, a systematic review and meta-analysis were conducted to evaluate the global prevalence of Giardia and Cryptosporidium in the effluent of municipal wastewater treatment plants (WWTPs). A total of 658 published papers were included in the initial search. After exclusion of unrelated articles, a meta-analysis was performed to determine the prevalence of Giardia, Cryptosporidium, levels of Giardia cysts and Cryptosporidium oocysts in the effluents with 22, 21, 14, and 11 articles, respectively. ‏The meta-analysis revealed that the global prevalence of Giardia and Cryptosporidium were 12.80% (95%CI: 10.74–14.85) and 25.90% (95%CI: 15.88–35.91) in the municipal WWTPs effluents, respectively. ‏The globally pooled concentration was also estimated to be 2.22 cyst/L (95%CI: 0.74–3.69) and 0.13 oocyst/L (95%CI: 0–0.026) for Giardia and Cryptosporidium, respectively. This implies that the monitoring and treatment activities for Giardia and Cryptosporidium removal are generally inadequate and the potential health risk of these parasites will remain. It is recommended that effective management measures in WWTPs along with the monitoring of effluent quality should be considered to eliminate the presence of Giardia and Cryptosporidium in effluent and prevent the adverse health implications.