Infectious Cryptosporidium parvum Oocysts in Final Reclaimed Effluent

Abstract

Water samples collected throughout several reclamation facilities were analyzed for the presence of infectious Cryptosporidium parvum by the focus detection method-most-probable-number cell culture technique. Results revealed the presence of infectious C. parvum oocysts in 40% of the final disinfected effluent samples. Sampled effluent contained on average seven infectious oocysts per 100 liters. Thus, reclaimed water is not pathogen free but contains infectious C. parvum.Reclaimed water (treated wastewater) is being utilized in the United States and throughout the world as an alternative nonpotable water source. In the United States, 18 states currently have standards and another 18 have guidelines for reclaimed water (8). These standards, for the most part, are based on total suspended solids and fecal coliforms. A variety of microbial pathogens are present in wastewater and can be detected in reclaimed water. Therefore, advanced treatment, including filtration and disinfection, is required to produce reclaimed water that does not have a negative impact on public health. In regulatory language, this means that pathogens are to be less than the limit of detection of the assay (8).Cryptosporidium parvum, a coccidian protozoan parasite, is a potential contaminant of reclaimed water. C. parvum oocysts have been found to be persistent in the environment and resistant to chlorination. Because of this, physical removal by chemical pretreatment and filtration is the primary means of reducing the level of oocysts in environmental water (6). A possible risk to human health exists if filtration fails to function efficiently. This risk is greater still with reclaimed water, as to date no monitoring for C. parvum oocysts has been required and little information is available on the filtration efficiency in these facilities. Recently, in the state of Florida, monitoring for protozoan parasites, including Cryptosporidium, once every 2 years for larger facilities and once every 5 years for smaller facilities has been mandated. Sampling is recommended at a single point following disinfection (2).In one study, C. parvum oocysts were detected in untreated wastewater (67% of the samples were positive) and in reclaimed water (25% of final effluent samples were positive) (5). However, only the presence of the oocysts was evaluated using fluorescence microscopy. Robertson et al. evaluated wastewater samples for viable C. parvum by using vital stains; 35% of the influent samples and 46% of the effluent samples contained viable oocysts (4). In the last few years, the focus detection method-most-probable-number (FDM-MPN) cell culture technique has been developed to test the oocyst infectivity because the previously employed methods did not accurately reflect the infectious nature of the oocysts (7). The objective of the present study was to demonstrate the presence of infectious C. parvum oocysts in final reclaimed effluent from six reclamation facilities in the United States by using the FDM-MPN cell culture technique.Samples were coll...

Reuse of effluent water—benefits and risks

“…Outside of an infected host they persist as dormant stages known as cysts or oocysts. There are several protozoan pathogens which have been isolated from wastewater and recycled water sources (Gennaccaro et al 2003). The most common detected are Entamoeba histolytica, Giardia intestinalis (formerly known as Giardia lamblia), and Cryptosporidium parvum (Toze 1997).…”

Aged HCT-8 Cell Monolayers Support Cryptosporidium parvum Infection

“…The human ileocecal adenocarcinoma HCT-8 cell line was previously found to support the greatest amount of Cryptosporidium parvum infection compared to several other cell lines (19,29) and is commonly used for Cryptosporidium infectivity assays (1,2,7,10,12,13,23,25,27,33). In the present study, we investigated the ability of freshly confluent (2-day-old) and aged (8-to 67-day-old) HCT-8 cell monolayers to support C. parvum infection.…”

“…The use of cell culture to study the intracellular development of Cryptosporidium was described over 2 decades ago (6). In addition to the study of Cryptosporidium biology, cell culture methods have been used to study Cryptosporidium inactivation by disinfectants (4,13,23,26,28), efficacy of chemotherapeutic agents (3,5,34,37), and detection of infectious oocysts in water samples (1,7,10,17). The developmental stages of the parasite in cell culture are detected using a variety of techniques, including immunofluorescent assay microscopy (27), flow cytometry (31), reverse transcription-PCR (22), and quantitative PCR (5,8,11,15).…”

Tratamiento biológico de aguas residuales: Principios, modelación y diseño

“…Los más pequeños ovoquistes de Criptosporidium pueden ser eliminados en un grado menor (80 a 96.8%), (Chauret et al, 1999;Mayer y Palmer, 1996). Gennaccaro et al, (2003) observaron que el 40% de los ovoquistes todavía son viables después del tratamiento completo de los lodos activados y desinfección con cloro. Se ha reportado una eliminación >97% para Entamoeba histolytica (Feachem et al, 1983).…”