<i>Cryptosporidium</i> Dose Response Studies: Variation Between Isolates

Teunis, Peter; Chappell, Cynthia L.; Okhuysen, Pablo C.

doi:10.1111/0272-4332.00014

Cited by 91 publications

(25 citation statements)

References 32 publications

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“…Recently, Di Giovanni and LeChevallier (8) reported different levels of cell culture infection for the isolates that they used to evaluate their quantitative PCR-cell culture assay. Human feeding trials showed similar differences with different C. parvum isolates displaying different infectivities (16,27). However, it must be noted that in our experiments the differences were sometimes small and the amount of data was sometimes limited.…”

Section: Discussionmentioning

confidence: 51%

Detection of Infectious Cryptosporidium Oocysts by Cell Culture Immunofluorescence Assay: Applicability to Environmental Samples

Schets

Engels

During

et al. 2005

Appl Environ Microbiol

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In the past few years many waterborne outbreaks related to Cryptosporidium have been described. Current methods for detection of Cryptosporidium in water for the most part rely on viability assays which are not informative concerning the infectivity of oocysts. However, for estimation of the risk of infection with Cryptosporidium this information is required. For environmental samples the oocyst counts are often low, and the oocysts have been exposed to unfavorable conditions. Therefore, determination of the infectivity of environmental oocysts requires an assay with a high level of sensitivity. We evaluated the applicability of in vitro cell culture immunofluorescence assays with HCT-8 and Caco-2 cells for determination of oocyst infectivity in naturally contaminated water samples. Cell culture assays were compared with other viability and infectivity assays. Experiments with Cryptosporidium oocysts from different sources revealed that there was considerable variability in infectivity, which was illustrated by variable 50% infective doses, which ranged from 40 to 614 oocysts, and the results indicated that not only relatively large numbers of fresh oocysts but also aged oocysts produced infection in cell cultures. Fifteen Dutch surface water samples were tested, and the cell culture immunofluorescence assays were not capable of determining the infectivity for the low numbers of naturally occurring Cryptosporidium oocysts present in the samples. A comparison with other viability assays, such as the vital dye exclusion assay, demonstrated that surrogate methods overestimate the number of infectious oocysts and therefore the risk of infection with Cryptosporidium. For accurate risk assessment, further improvement of the method for detection of Cryptosporidium in water is needed.Cryptosporidium is one of the important waterborne causative agents of gastrointestinal illness in humans (6, 10). More than 50 outbreaks of cryptosporidiosis associated with either contaminated drinking water or recreational water have been reported worldwide since 1983 (20). In immunocompetent individuals cryptosporidial diarrhea is usually self-limiting, lasting for about 3 weeks, but infected immunocompromised humans may develop severe and potentially fatal illness (5). At present, no consistently effective, approved therapeutic agent with anticryptosporidial activity is available.Cryptosporidium oocysts are ubiquitous in surface water used for recreation or drinking water production (9, 21). They are extremely resistant to chlorination at the concentrations commonly used for drinking water and swimming pool water disinfection (13). The number of oocysts in finished water is usually low but relevant for public health, and the concentrations are below the detection limit of the method used. Therefore, Dutch drinking water legislation requires drinking water companies to perform a quantitative risk assessment for Cryptosporidium, based on the concentration of oocysts in the source water and the efficiency of drinking water treatment proce...

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Section: Discussionmentioning

confidence: 51%

Detection of Infectious Cryptosporidium Oocysts by Cell Culture Immunofluorescence Assay: Applicability to Environmental Samples

Schets

Engels

During

et al. 2005

Appl Environ Microbiol

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“…Because of data limitations, x for E. coli, Salmonella and rotavirus was recommended to be 0.79 (Teunis et al, 2002), and y was determined to be 20 years old, based on field investigations in Si-yuan University. Other parameters such as 'a' and 'b' were suggested to be 3.56 and − 53.2, respectively, by Teunis et al (2002), while 'c' and 'β' were recommended by the WHO studies (Murray and Lopez, 1996) to be − 0.1685 and 0.04, respectively.…”

Section: Infection Rate (Pinf)mentioning

confidence: 99%

Application of disease burden to quantitative assessment of health hazards for a decentralized water reuse system

Gao

Chen

Wang

et al. 2016

Science of The Total Environment

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The aim of this article is to introduce the methodology of disease burden (DB) to quantify the health impact of microbial regrowth during wastewater reuse, using the case study of a decentralized water reuse system in Xi'an Si-yuan University, located in Xi'an, China. Based on field investigation findings, Escherichia coli (E. coli), Salmonella and rotavirus were selected as typical regrowth pathogens causing potential health hazards during the reuse of reclaimed water. Subsequently, major exposure routes including sprinkler irrigation, landscape fountains and toilet flushing were identified. Mathematical models were established to build the relationship between exposure dose and disease burden by calculating the disability adjusted life year (DALY). Results of disease burden for this case study show that DALYs attributed to E. coli were significantly greater than those caused by other pathogens, and DALYs associated with sprinkler irrigation were higher than those originating from other routes. A correlation between exposure dose and disease was obtained by introducing a modified calculation of morbidity, which can extend the assessment endpoint of health risk to disease burden from the conventional infection rate.

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“…After heavy rainfall in 1998, elevated levels of Cryptosporidium oocysts and Giardia cysts were detected within the raw and filter water supply. This was a particular concern because of their resistance to chlorine disinfection (LeChevallier & Au 2004) and low infectious dose (Teunis et al 2002b). There have not been any other occurrences in the drinking water supply; however, there has been an ongoing focus on the STPs and the other sources of Cryptosporidium and Giardia in the catchment to monitor and manage risks to water quality.…”

Section: Introductionmentioning

confidence: 99%

Estimating the risk from sewage treatment plant effluent in the Sydney catchment area

Akker

Whiffin

Cox

et al. 2011

Water Science and Technology

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This study employed Quantitative Microbial Risk Assessment (QMRA) to estimate the gastrointestinal risks associated with Cryptosporidium and Giardia discharged from three STPs located within the Lake Burragorang catchment. The QMRA considered baseline and various hazardous event scenarios (e.g. plant failure and heavy rainfall). Under baseline conditions, the combined effect of constructed barriers, catchment barriers and dilution reduced pathogen numbers from the discharge of all three STPs by 10 to 14 orders of magnitude. This was sufficient for the risk to be well below currently mooted benchmarks of 'tolerable risk', even when relatively conservative assumptions were applied. For all hazardous event scenarios, the level of risk remained low, which illustrated the benefit of multiple barriers. Provisionally it appears that the STPs currently discharging into the waterways of the catchment do not pose an unacceptable or unmanageable risk to Sydney's drinking water consumers.Key words 9 9 9 9 Cryptosporidium, drinking water catchment, Giardia, risk assessment, sewage

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Cryptosporidium Dose Response Studies: Variation Between Isolates

Cited by 91 publications

References 32 publications

Detection of Infectious Cryptosporidium Oocysts by Cell Culture Immunofluorescence Assay: Applicability to Environmental Samples

Detection of Infectious Cryptosporidium Oocysts by Cell Culture Immunofluorescence Assay: Applicability to Environmental Samples

Application of disease burden to quantitative assessment of health hazards for a decentralized water reuse system

Estimating the risk from sewage treatment plant effluent in the Sydney catchment area

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