Detection of Giardia duodenalis in sewage of Ensenada, Baja California, Mexico

G. duodenalis is a pathogenic protozoan that affects animals and humans. This microorganism is transmitted by the fecal-oral route when it is ingested contaminated water or food. Giardia cysts are infectious, resistant to extreme environmental conditions, and their presence in sewage depends on the technologies used in the treatment plants. This study analyzes G. duodenalis and total (TC) and fecal (FC) coliforms in wastewater effluents of treatment plants (The Northeast, Gallo, Naranjo, Sauzal) and Emilio López Zamora dam of Ensenada Baja California. Water samples were taken monthly from June to November of 2019. Giardia was detected using the direct immunofluorescence (DFA) technique. TC and FC quantification were carried out according to the official Mexican standard (NOM- 001-SEMARNAT-1996). Giardia was observed in Gallo (80-280 cysts/L), Sauzal (0-240 cysts/L), and Naranjo (0-360 cysts/L) effluents from July to November. FC was generally within the official standard (NOM-003), less than 1000 FC/100 mL for waters that will have indirect or occasional contact with the human being. Except for Naranjo effluent, where coliforms exceeded 1800 NMP/100 mL.