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      Bayesian risk assessment model of human cryptosporidiosis cases following consumption of raw Eastern oysters ( Crassostrea virginica) contaminated with Cryptosporidium oocysts in the Hillsborough River system in Prince Edward Island, Canada

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          Abstract

          Cryptosporidium spp. has been associated with foodborne infectious disease outbreaks; however, it is unclear to what extent raw oyster consumption poses a risk to public health. Control of Cryptosporidium in shellfish harvest seawater in Canada is not mandatory and, despite relay/depuration processes, the parasite can remain viable in oysters for at least a month (depending on initial loads and seawater characteristics). Risks of human infection and illness from exposure to oysters contaminated with Cryptosporidium oocysts were assessed in a Bayesian framework. Two data sets were used: counts of oocysts in oysters harvested in Approved, Restricted, and Prohibited zones of the Hillsborough River system; and oocyst elimination rate from oysters exposed to oocysts in laboratory experiments. A total of 20 scenarios were assessed according to number of oysters consumed in a single serving (1, 10 and 30) and different relay times. The median probability of infection and developing cryptosporidiosis (e.g. illness) due to the consumption of raw oysters in Prince Edward Island was zero for all scenarios. However, the 95th percentiles ranged from 2% to 81% and from 1% to 59% for probability of infection and illness, respectively. When relay times were extended from 14 to 30 days and 10 oysters were consumed in one serving from the Restricted zones, these probabilities were reduced from 35% to 16% and from 15% to 7%, respectively. The 14-day relay period established by Canadian authorities for harvesting in Restricted zones seems prudent, though insufficient, as this relay period has been shown to be enough to eliminate fecal coliforms but not Cryptosporidium oocysts, which can remain viable in the oyster for over a month. Extending relay periods of 14 and 21 days for oysters harvested in Restricted zones to 30 days is likely insufficient to substantially decrease the probability of infection and illness. The highest risk was found for oysters that originated in Prohibited zones. Our findings suggest that Cryptosporidium oocysts are a potential cause of foodborne infection and illness when consuming raw oysters from Hillsborough River, one of the most important oyster production bays on Prince Edward Island. We discuss data gaps and limitations of this work in order to identify future research that can be used to reduce the uncertainties in predicted risks.

          Highlights

          • Risk of infection and illness of cryptosporidiosis in humans by consuming raw oysters from PEI is likely to be negligible.

          • Depuration time of 14 days might not be enough to reduce Cryptosporidium oocysts contamination in oysters in bays of PEI.

          • More field data need to be obtained to reduce uncertainties in predicted risks.

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          Most cited references41

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          Inference from Iterative Simulation Using Multiple Sequences

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            Cryptosporidium species in humans and animals: current understanding and research needs.

            Cryptosporidium is increasingly recognized as one of the major causes of moderate to severe diarrhoea in developing countries. With treatment options limited, control relies on knowledge of the biology and transmission of the members of the genus responsible for disease. Currently, 26 species are recognized as valid on the basis of morphological, biological and molecular data. Of the nearly 20 Cryptosporidium species and genotypes that have been reported in humans, Cryptosporidium hominis and Cryptosporidium parvum are responsible for the majority of infections. Livestock, particularly cattle, are one of the most important reservoirs of zoonotic infections. Domesticated and wild animals can each be infected with several Cryptosporidium species or genotypes that have only a narrow host range and therefore have no major public health significance. Recent advances in next-generation sequencing techniques will significantly improve our understanding of the taxonomy and transmission of Cryptosporidium species, and the investigation of outbreaks and monitoring of emerging and virulent subtypes. Important research gaps remain including a lack of subtyping tools for many Cryptosporidium species of public and veterinary health importance, and poor understanding of the genetic determinants of host specificity of Cryptosporidium species and impact of climate change on the transmission of Cryptosporidium.
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              Epidemiology of seafood-associated infections in the United States.

              Seafood is part of a healthful diet, but seafood consumption is not risk-free. Seafood is responsible for an important proportion of food-borne illnesses and outbreaks in the United States. Seafood-associated infections are caused by a variety of bacteria, viruses, and parasites; this diverse group of pathogens results in a wide variety of clinical syndromes, each with its own epidemiology. Some seafood commodities are inherently more risky than others, owing to many factors, including the nature of the environment from which they come, their mode of feeding, the season during which they are harvested, and how they are prepared and served. Prevention of seafood-associated infections requires an understanding not only of the etiologic agents and seafood commodities associated with illness but also of the mechanisms of contamination that are amenable to control. Defining these problem areas, which relies on surveillance of seafood-associated infections through outbreak and case reporting, can lead to targeted research and help to guide control efforts. Coordinated efforts are necessary to further reduce the risk of seafood-associated illnesses. Continued surveillance will be important to assess the effectiveness of current and future prevention strategies.
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                Author and article information

                Contributors
                Journal
                Food Waterborne Parasitol
                Food Waterborne Parasitol
                Food and Waterborne Parasitology
                Elsevier
                2405-6766
                19 March 2020
                June 2020
                19 March 2020
                : 19
                : e00079
                Affiliations
                [a ]Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, PEI, Canada
                [b ]Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, PEI, Canada
                Author notes
                [* ]Corresponding author at: Department of Health Management, University of Prince Edward Island, 550 University Avenue Charlottetown, PE C1A 4P3, Canada. tpatanasatie@ 123456upei.ca
                Article
                S2405-6766(20)30008-1 e00079
                10.1016/j.fawpar.2020.e00079
                7109418
                c75f8411-0362-41a5-ad24-e190c66a0b32
                © 2020 The Authors. Published by Elsevier Inc. on behalf of International Association of Food and Waterborne Parasitology.

                This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

                History
                : 25 July 2019
                : 16 March 2020
                : 17 March 2020
                Categories
                Research Article

                risk assessment,cryptosporidium,bayesian inference,human infection,oyster

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