Giardia Cysts in Wastewater Treatment Plants in Italy

Abstract

Reductions in annual rainfall in some regions and increased human consumption have caused a shortage of water resources at the global level. The recycling of treated wastewaters has been suggested for certain domestic, industrial, and agricultural activities. The importance of microbiological and parasitological criteria for recycled water has been repeatedly emphasized. Among water-borne pathogens, protozoa of the genera Giardia and Cryptosporidium are known to be highly resistant to water treatment procedures and to cause outbreaks through contaminated raw or treated water. We conducted an investigation in four wastewater treatment plants in Italy by sampling wastewater at each stage of the treatment process over the course of 1 year. The presence of the parasites was assessed by immunofluorescence with monoclonal antibodies. While Cryptosporidium oocysts were rarely observed, Giardia cysts were detected in all samples throughout the year, with peaks observed in autumn and winter. The overall removal efficiency of cysts in the treatment plants ranged from 87.0 to 98.4%. The removal efficiency in the number of cysts was significantly higher when the secondary treatment consisted of active oxidation with O 2 and sedimentation instead of activated sludge and sedimentation (94.5% versus 72.1 to 88.0%; P ‫؍‬ 0.05, analysis of variance). To characterize the cysts at the molecular level, the ␤-giardin gene was PCR amplified, and the products were sequenced or analyzed by restriction. Cysts were typed as assemblage A or B, both of which are human pathogens, stressing the potential risk associated with the reuse of wastewater.

Occurrence of Cryptosporidium Oocysts and Giardia Cysts in Sewage in Norway

“…Failure to obtain positive PCR results from wastewater samples containing Cryptosporidium oocysts has also been reported by others (1). It is unknown whether this was due to insufficient DNA or inhibition of the PCR.…”

“…Giardia duodenalis cysts has been used in a variety of studies to further elucidate aspects of the epidemiology, both conventional and molecular, of these parasites in particular populations or geographic regions (1,20). Additionally, such analyses can be used as an indirect method of assessing the occurrence of these infections in human populations (12,17,18).…”

Occurrence of Cryptosporidium hominis in pigeons (Columba livia)

“…Molecular studies have shown that the majority of human cases are caused by C. hominis and C. parvum (Anonymous 2000, McLauchlin et al 2000. The oocysts of this parasite can be readily found in sludge, raw sewage, sewage effluents, drinking water and recreational waters (Bukhari et al 1997, Fayer et al 2000, Robertson et al 2000, Caccib et al 2003, and may represent a public health risk in developed and developing countries (LeChevalier et al 1991a, b).…”

Distribution of Giardia duodenalis Genotypes and Subgenotypes in Raw Urban Wastewater in Milwaukee, Wisconsin

“…Human sewage has been considered a source of Giardia cyst contamination in water. In Canada and Italy, a high prevalence (73 to 100%) of Giardia cysts was reported in raw sewage samples (4,14,34). The public health importance and contamination sources of Giardia cysts found in water, however, are largely unclear, because very few studies have been carried out to genetically characterize the Giardia cysts in water.…”

“…In recent years, several attempts have been made to detect and differentiate Giardia spp. in environmental samples by using PCR techniques (4,31,34). The distribution of Giardia spp.…”