Viral Contamination Of Shellfish Research Articles

Surveillance of human norovirus in oysters collected from production area in Shandong Province, China during 2017–2018

Human norovirus (HuNoV) is the leading cause of non-bacterial gastroenteritis worldwide. Oysters are known food-related vehicles for HuNoV transmission. However, there are few data available on the viral contamination of shellfish from production areas in China. A one-year monitoring program was carried out to detect and characterize HuNoV contamination in oysters, collected from two shellfish commercial harvesting areas in Shandong province, China. Oysters were sampled every month from July 2017 to August 2018. From the 356 oyster samples, HuNoV was detected in 16.9% (60/356) using reverse transcription-qPCR. Of the 60 positive samples, 43.3% (26/60) were positive for HuNoV genogroup I (GI) only and 31.7% (19/60) were positive for genogroup II (GII) only. Both GI and GII were detected in 25.0% (15/60) samples. The majority (65.0%, 39/60) of positive samples were collected in winter months (November–December). There was no significant correlation between the detection of HuNoV in shellfish and the pH or fecal coliforms levels in seawater. Using next-generation sequencing, several HuNoV genotypes were identified including capsid genotypes GI.5, GI.6, GII.2, GII.3, GII.4_Sydney 2012, GII.13 and GII.14. These Results indicate that monitoring of HuNoV in oyster production area is necessary to ensure the safety of shellfish prior to distribution to consumers.

Virus entériques humains et coquillages

Human enteric viruses and shellfish Human enteric viruses discharged in raw sewage are hightly resistant and may be detected in surface waters, coastal areas and shellfish. Whereas noroviruses, responsible for relatively benign acute gastroentritis, are the most common agents implicated in shellfish borne outbreaks, other human viruses which cause severe human diseases, such as hepatitis A virus, may also be transmitted. Environmental studies have demonstrated that virus concentrations detected in shellfish are higher than in surrounding waters. This concentration may explain the high prevalence of noroviruses detected in various shellfish species collected in different countries. If many questions remain regarding viral contamination of shellfish, the most important seems to be the prevention of coastal areas contamination by human sewages.

Prevalence of Human Enteric Viruses and a Potential Indicator of Contamination in Shellfish in China

AbstractThe objectives of this study were to quantify enteric viruses in shellfish along the Chinese coast and find an indicator of viral contamination in shellfish. One hundred sixty‐two samples were collected in August from 10 cities. Hepatitis A virus (HAV), norovirus (NV), rotavirus (RV), poliovirus (PV), astrovirus (AsV) and adenovirus (AdV) were detected by polymerase chain reaction (PCR) and confirmed by sequencing. The percentage of positive samples for each virus was as follows: HAV 5%, NV 12%, RV 7%, PV 15%, AsV 6% and AdV 9%. The six species of shellfish were contaminated with different viruses. PV showed a significant correlation with other viruses, with the exception of RV (P < 0.05). Contamination of shellfish with human enteric viruses was common across a large geographical region of China, indicating a potential public health threat from seafood. The data confirm the potential to monitor the food safety of shellfish by using PV as an index of enteric virus contamination.Practical ApplicationsEnteric viruses are one of foodborne pathogens transmitted by bivalve shellfish, which pose a severe potential risk for consumers, as well as a serious problem facing researchers. China leads the worldwide production of shellfish. Therefore, the safety of shellfish harvested in China is particularly important. Norovirus, hepatitis A virus, rotavirus, adenovirus, poliovirus and astrovirus are introduced to assess the seafood safety by documenting risks for transmission of enteric viruses in shellfish along the Chinese coast. Of which, poliovirus could be one of these potential indicator to present human enteric virus contamination in the countries where oral polio vaccines are used.

Impact of Xynthia Tempest on Viral Contamination of Shellfish

Viral contamination in oyster and mussel samples was evaluated after a massive storm with hurricane wind named "Xynthia tempest" destroyed a number of sewage treatment plants in an area harboring many shellfish farms. Although up to 90% of samples were found to be contaminated 2 days after the disaster, detected viral concentrations were low. A 1-month follow-up showed a rapid decrease in the number of positive samples, even for norovirus.

Inactivation of a calicivirus and enterovirus in shellfish by high pressure

Abstract This study demonstrates the potential of high pressure (HP) processing to reduce viral contamination in shellfish. Bovine enterovirus, which is structurally similar to hepatitis A virus, was more pressure-resistant than feline calicivirus, a surrogate for norovirus. Both viruses were more pressure-resistant when treated in “naturally” contaminated mussels and oysters, compared to seawater and culture medium, suggesting that the medium can have a significant protective effect against HP treatment. Treatment at pressures of 250 MPa showed only a limited inactivation of either virus in shellfish, suggesting that relatively mild HP treatments (approximately 260 MPa) currently used for the commercial processing of oysters, principally to assist the shucking process, may be insufficient to ensure the safety of shellfish for human consumption, particularly in relation to human pathogenic viruses. Industrial relevance High pressure (HP) processing is increasingly being used in the commercial processing of oysters, principally to assist the opening or shucking of oysters. Little is known about the effect of HP treatment on pathogens in shellfish, particularly human enteric viruses, which are the predominant cause of shellfish-borne disease. This article demonstrates the inactivation of surrogate animal viruses, as potential models for noroviruses and hepatitis A virus, by HP processing and compares the efficacy of inactivation when viruses are treated in culture medium, seawater and shellfish. The potential of HP processing to reduce viral contamination in shellfish is discussed in light of these findings.

Nested multiplex PCR assay for detection of human enteric viruses in shellfish and sewage

Environmental samples and contaminated shellfish present frequently low concentrations of more than one viral species. For this reason, a nested multiplex RT-PCR was developed for the detection of adenoviruses, enteroviruses and hepatitis A viruses in different environmental samples such as urban sewage and shellfish. This assay will save time and cost for detection of these enteric viruses with a smaller sample volume, which otherwise can be a limiting factor in routine analysis. The limit of detection was approximately 1 copy for adenovirus and 10 copies for enterovirus and hepatitis A virus per PCR reaction using titrated cell-cultured viruses as template material. In shellfish and environmental samples, this multiplex PCR was optimized to detect all three viruses simultaneously when the concentration of each virus was equal or lower than 1000 copies per PCR reaction. This is the level found predominantly in the environment and in shellfish when the numbers of fecal bacterial and phage indicators are low. The detection of human adenoviruses by PCR has been suggested as a molecular index of fecal contamination of human origin in the environment and food and the multiplex assay developed may be a tool for evaluating the presence of viral contamination in shellfish and water and to expand microbiological control to include viral markers.

Distribution of human virus contamination in shellfish from different growing areas in Greece, Spain, Sweden, and the United Kingdom.

Viral pollution in shellfish has been analyzed simultaneously across a wide range of geographical regions, with emphasis on the concomitant variations in physicochemical characteristics and social features. The methods for sample treatment and for the detection of human enteric viruses were optimized by the participating laboratories. The second part of this study involves the selection of a protocol for virus detection, which was validated by analyzing the distribution and concentration of human viral pathogens under diverse conditions during an 18-month period in four European countries. Shellfish-growing areas from diverse countries in the north and south of Europe were defined and studied, and the microbiological quality of the shellfish was analyzed. Human adenovirus, Norwalk-like virus, and enterovirus were identified as contaminants of shellfish in all the participating countries. Hepatitis A virus was also isolated in all areas except Sweden. The seasonal distribution of viral contamination was also described. Norwalk-like virus appeared to be the only group of viruses that demonstrated seasonal variation, with lower concentrations occurring during warm months. The depuration treatments currently applied were shown to be adequate for reducing Escherichia coli levels but ineffective for the elimination of viral particles. The human adenoviruses detected by PCR correlate with the presence of other human viruses and could be useful as a molecular index of viral contamination in shellfish.

Comparative analysis of viral pathogens and potential indicators in shellfish

Shellfish can be responsible of outbreaks of infectious diseases and current health measures do not guarantee the absence of viral pathogens in this product. Here we examine the presence of pathogenic viruses and potential indicators in shellfish in a comparative analysis. Sixty shellfish samples collected in three areas with different levels of faecal contamination were analysed for Escherichia coli, total coliforms, Clostridium perfringens, somatic coliphages, F-specific phages of RNA (F-RNA), bacteriophages infecting Bacteroides fragilis RYC2056, human adenovirus, enterovirus and hepatitis A virus (HAV). Viruses were eluted in a glycine buffer at pH 10. The overall percentage of viral pathogens detected was 47% for human adenoviruses, 19% for enteroviruses and 24% for HAV. Since all the samples positive for enterovirus and HAV were also positives for human adenovirus, the latter may be considered useful as a molecular index of viral contamination in shellfish. No significant differences in the bioaccumulation of bacteria and bacteriophages for oysters or mussels were observed. It was found that the probability of detection of any of the pathogenic virus decreases as the temperature of shellfish growing waters increases. However, the probability of detecting viruses increases when phages of B. fragilis are found. Although more data are needed in order to fulfil the need of viral indicators for controlling the presence of human viruses in shellfish, the obtained results indicate that phages infecting B. fragilis RYC2056 could be a suitable group of bacteriophages to be used as an indicator of the presence of viruses in shellfish.

Viral contamination of shellfish: evaluation of methods and analysis of bacteriophages and human viruses

Viral outbreaks attributed to the consumption of contaminated shellfish have been clearly demonstrated. Thirty-five samples of mussels collected from areas with two different levels of faecal pollution were analysed for somatic coliphages, F-RNA phages and bacteriophages infecting Bacteroides fragilis HSP40 and RYC2056 following standardised protocols, and for enterovirus, human adenovirus and hepatitis A virus by nucleic acid amplification (Nested-PCR and RT-PCR). Four methods for viral recovery from shellfish have been compared. The first method is based on borate buffer at pH 9.5 as eluent, the second is based on glycine buffer at pH 10 as eluent, a third method is based on glycine buffer at pH 7.5 and changes in conductivity and the fourth method on nutritive broth with Tween 80 as eluent. The results obtained were analysed statistically and the method based in glycine buffer at pH 10 seems to be the most efficient and useful for the recovery of phages and human viruses. The results also show a different pattern in the proportions between the viral parameters when the source of the faecal pollution is close to or distant from the shellfish growing area.