Assessing the risk posed by oocysts in drinking water

Haas, Charles N.; Crockett, Christopher S.; Rose, Joan B.; Gerba, Charles P.; Fazil, Aamir

doi:10.1002/j.1551-8833.1996.tb06619.x

Cited by 158 publications

(77 citation statements)

References 32 publications

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“…For comparison, the ID 50 for calf Cryptosporidium parvum in humans is about 150 oocysts (calculated from the dose-response curve of Haas et al (1996) applied to the human infectivity data of DuPont et al (1995)) and for Giardia lamblia, the ID 50 is about 35 cysts (using the dose-response curve from Rose and Gerba 1991).…”

Section: The Number Of Prp Bse Molecules Comprising a Human Oral Id 50mentioning

confidence: 99%

Development of a risk assessment for BSE in the aquatic environment

et al. 1998

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Bovine spongiform encephalopathy (BSE) is believed to be transmitted by the ingestion of proteinaceous agents called prions which accumulate in the brain and spinal cord of infected bovines. Concern has been expressed about the risks of transmission of BSE to humans through BSE prions discharged to the aquatic environment from rendering plants, abattoirs and landfills. The disease‐related form of the prion protein is relatively resistant to degradation, and infectivity decays rather slowly in the environment. Levels of disinfection used for drinking water treatment would have little effect. This paper presents the assumptions which were used to model the risks from a rendering plant disposing of cull cattle carcasses in the catchment of a chalk aquifer which is used for a drinking water abstraction. The risk assessment approach focused on identifying the hydrogeological and physical barriers which would contribute to preventing BSE infectivity gaining entry to the aquifer. These barriers included inactivation of BSE agent by the rendering process, removal from the effluent by treatment at the plant, filtration and adsorption in the clay and chalk, and dilution in the ground water. The importance in environmental risk assessment of the cow‐to‐man species barrier is considered. Two key conclusions about the environmental behaviour of the BSE agent are that prion proteins are ‘sticky’ and bind to particulates, and that the millions of BSE prion molecules comprising a human oral ID50 are subject to some degree of dispersion and hence dilution in the environment. Assuming the rendering plant processes 2000 cull cattle carcasses per week, the risks to drinking water consumers were estimated to be remote. Indeed, even using worst case assumptions an individual would have to consume 2 l d−1 of tap water for 45 million years to have a 50% chance of infection through drinking water drawn from the aquifer.

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Section: The Number Of Prp Bse Molecules Comprising a Human Oral Id 50mentioning

confidence: 99%

Development of a risk assessment for BSE in the aquatic environment

et al. 1998

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“…In fact, of the three different methods used to evaluate microbial risks, microbiology laboratory analysis, epidemiological studies and QMRA, only the first two have been applied to helminth data (Tellez et al 1997;Howard et al 2002;Berhe et al 2004). In contrast, a number of human doseresponse relationships have been developed for bacteria, viruses, and protozoa Rose et al 1991;Haas et al 1993Haas et al , 1996Haas et al , 1999bCrockett et al 1996;Medema et al 1996;Teunis et al 1999). From a literature survey, it seems that human dose-response relationships for Ascaris or Taenia (types of helminth) have not been developed yet (NRC 2002).…”

Section: Introductionmentioning

confidence: 99%

Application of Helminth ova infection dose curve to estimate the risks associated with biosolid application on soil

Navarro

Jiménez

Lucario

et al. 2008

Journal of Water and Health

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Helminth ova (HO) are the main biological concern when reusing sludge for agricultural production.Worldwide sludge regulations consider a permissible range of 0.25-1 HO/gTS. Such limits are unaffordable to most developing countries, due to high helminth ova content in sludge, and the lack of viable technology to inactivate them as needed. The quantitative microbial risk assessment (QMRA) is a useful tool to estimate the risk of treated sludge, considering feasible and viable limits.QMRA, however, has not been applied before for HO because no dose-infection curve was available.Therefore, the objectives of this paper are: to build up a risk-based model designed for untreated wastewater exposure (i.e., land irrigation) using Ascaris lumbricoides eggs as indicators for HO, and apply the results to assess health risk (i.e., Ascaris lumbricoides infection) associated with consumption of crops grown on biosolid-enriched soil. Data showed that it may be feasible to update HO threshold in biosolids from developing countries without significantly increasing risks.To reduce health risk from HO, it may be wiser to achieve feasible and evidence-based standards, than to set unaffordable limits in these countries. QMRA data suggested additional protection measures, such as biosolid application rates, crop restriction, and produce better washing practices.

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“…18 More recent data, however, suggest that even low doses can lead to infection and illness in healthy volunteers. 19,20 Although Cryptosporidium is only one among many pathogens annually causing outbreaks of drinking water-associated disease and serious illness, its emergence has influenced federal and state policy-making since the mid-1990s. Public anxiety over Cryptosporidium motivated significant federal and state activity to learn more about the pathogen and examine the adequacy of current water quality regulations, even as the number of drinking water-associated outbreaks attributable to Cryptosporidium decreased in 1995 and 1996, 21 the most recent years for which complete data are available, and the risk to persons with HIV/AIDS declined with the increased use of highly active antiretroviral therapy.…”

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confidence: 99%

Water quality laws and waterborne diseases: Cryptosporidium and other emerging pathogens

Gostin

Lazzarini

Neslund³

et al. 2000

Am J Public Health

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Waterborne diseases, such as cryptosporidiosis, cause many cases of serious illness in the United States annually. Water quality is regulated by a complex system of federal and state legal provisions and agencies, which has been poorly studied. The authors surveyed state and territorial agencies responsible for water quality about their laws, regulations, policies, and practices related to water quality and surveillance of cryptosporidiosis related to drinking water. In this commentary they review the development and current status of federal drinking water regulations, identify conflicts or gaps in legal authority between federal agencies and state and territorial agencies, and describe court-imposed limitations on federal authority with regard to regulation of water quality. Recommendations are made for government actions that would increase the efficiency of efforts to ensure water quality; protect watersheds; strengthen waterborne disease surveillance; and protect the health of vulnerable populations.

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Assessing the risk posed by oocysts in drinking water

Cited by 158 publications

References 32 publications

Development of a risk assessment for BSE in the aquatic environment

Development of a risk assessment for BSE in the aquatic environment

Application of Helminth ova infection dose curve to estimate the risks associated with biosolid application on soil

Water quality laws and waterborne diseases: Cryptosporidium and other emerging pathogens

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