Multicenter Collaborative Trial Evaluation of a Method for Detection of Human Adenoviruses in Berry Fruit

QMRA of adenovirus in drinking water at a drinking water treatment plant using UV and chlorine dioxide disinfection

According to the Dutch Drinking Water Act of 2011, Dutch drinking water suppliers must conduct a Quantitative Microbial Risk Assessment (QMRA) for infection by the following index pathogens: enterovirus, Campylobacter, Cryptosporidium and Giardia at least once every four years in order to assess the microbial safety of drinking water. The health-based target for safe drinking water is set at less than one infection per 10 000 persons per year. At Evides Water Company, concern has arisen whether their drinking water treatment, mainly based on UV inactivation and chlorine dioxide, reduces levels of adenovirus (AdV) sufficiently. The main objective was, therefore, to conduct a QMRA for AdV. Estimates of the AdV concentrations in source water were based on enumeration of total AdV by integrated cell culture PCR (iccPCR), most probable number PCR (mpnPCR) and quantitative PCR (qPCR), and on enumeration of AdV40/41 by mpnPCR and qPCR. AdV40/41 represents a large fraction of total AdV and only a small fraction of AdV is infectious (1/1700). By comparison of literature data and plant scale data, somatic coliphages appeared a good, conservative indicator for AdV disinfection by UV irradiation. Similarly, bacteriophage MS2 appeared to be a good, conservative indicator for disinfection by chlorine dioxide. Literature data on the efficiency of chlorine dioxide disinfection were fitted with the extended HOM model. Chlorine dioxide disinfection at low initial concentrations (0.05-0.1 mg/l) was found to be the major treatment step, providing sufficient treatment on its own for compliance with the health-based target. UV disinfection of AdV at 40 mJ/cm² or 73 mJ/cm² was insufficient without chlorine dioxide disinfection.

Viral Contamination of Food

A review of the relevant foodborne viruses is presented. Published data from scientific journals as well as the data presented in official reports and published on the Internet were used for this review. In the review, information is given for the main foodborne viruses, implicated virus species, and food matrices involved, some history data are given, as well as modes of transmission, and sources of the virus presence in food. Results of surveys on the presence of viruses in different kind of foods commodities (fresh produces and shellfish) and in some cases connections to caused outbreaks are presented. Also, possible zoonotic infection and implicated viruses that could be transmitted through food are given. Human Norovirus followed by hepatitis A virus are the most common foodborne viruses, which are transmitted by food consumed raw, such as shellfish, fresh vegetables, and berry fruit. In developed countries, hepatitis E virus is increasingly being recognized as an emerging viral foodborne pathogen that includes zoonotic transmission via pork products. The existing knowledge gaps and the major future expectations in the detection and surveillance of foodborne viruses are mentioned.

Monitoring of Extraction Efficiency by a Sample Process Control Virus Added Immediately Upon Sample Receipt

When analysing food samples for enteric viruses, a sample process control virus (SPCV) must be added at the commencement of the analytical procedure, to verify that the analysis has been performed correctly. Samples can on occasion arrive at the laboratory late in the working day or week. The analyst may consequently have insufficient time to commence and complete the complex procedure, and the samples must consequently be stored. To maintain the validity of the analytical result, it will be necessary to consider storage as part of the process, and the analytical procedure as commencing on sample receipt. The aim of this study was to verify that an SPCV can be recovered after sample storage, and thus indicate the effective recovery of enteric viruses. Two types of samples (fresh and frozen raspberries) and two types of storage (refrigerated and frozen) were studied using Mengovirus vMC0 as SPCV. SPCV recovery was not significantly different (P > 0.5) regardless of sample type or duration of storage (up to 14 days at -20 °C). Accordingly, samples can be stored without a significant effect on the performance of the analysis. The results of this study should assist the analyst by demonstrating that they can verify that viruses can be extracted from food samples even if samples have been stored.

Sample preparation prior to molecular amplification: complexities and opportunities

Molecular amplification using Reverse Transcription quantitative Polymerase Chain Reaction (RT-qPCR) is currently considered as the gold standard to detect enteric human pathogenic viruses such as norovirus and hepatitis A virus in food and water. However, the molecular-based detection requires an adequate sampling strategy and a sample preparation specific for viruses. Sampling for enteric human viruses in water and food should not necessarily follow bacterial sampling plans. The development of a reference detection method including sample preparation as proposed in ISO/TS 15216 represents a milestone to facilitate the evaluation of the performance and eventually validation of future virus detection methods. The potential viral infectivity linked to a positive PCR result is a remaining issue and pretreatments allowing the differentiation of infectious viruses would be useful for future risk assessments.

Tracing enteric viruses in the European berry fruit supply chain

In recent years, numerous foodborne outbreaks due to consumption of berry fruit contaminated by human enteric viruses have been reported. This European multinational study investigated possible contamination routes by monitoring the entire food chain for a panel of human and animal enteric viruses. A total of 785 samples were collected throughout the food production chain of four European countries (Czech Republic, Finland, Poland and Serbia) during two growing seasons. Samples were taken during the production phase, the processing phase, and at point-of-sale. Samples included irrigation water, animal faeces, food handlers' hand swabs, swabs from toilets on farms, from conveyor belts at processing plants, and of raspberries or strawberries at points-of-sale; all were subjected to virus analysis. The samples were analysed by real-time (reverse transcription, RT)-PCR, primarily for human adenoviruses (hAdV) to demonstrate that a route of contamination existed from infected persons to the food supply chain. The analyses also included testing for the presence of selected human (norovirus, NoV GI, NoV GII and hepatitis A virus, HAV), animal (porcine adenovirus, pAdV and bovine polyomavirus, bPyV) and zoonotic (hepatitis E virus, HEV) viruses. At berry production, hAdV was found in 9.5%, 5.8% and 9.1% of samples of irrigation water, food handlers' hands and toilets, respectively. At the processing plants, hAdV was detected in one (2.0%) swab from a food handler's hand. At point-of-sale, the prevalence of hAdV in fresh raspberries, frozen raspberries and fresh strawberries, was 0.7%, 3.2% and 2.0%, respectively. Of the human pathogenic viruses, NoV GII was detected in two (3.6%) water samples at berry production, but no HAV was detected in any of the samples. HEV-contaminated frozen raspberries were found once (2.6%). Animal faecal contamination was evidenced by positive pAdV and bPyV assay results. At berry production, one water sample contained both viruses, and at point-of-sale 5.7% and 1.3% of fresh and frozen berries tested positive for pAdV. At berry production hAdV was found both in irrigation water and on food handler's hands, which indicated that these may be important vehicles by which human pathogenic viruses enter the berry fruit chain. Moreover, both zoonotic and animal enteric viruses could be detected on the end products. This study gives insight into viral sources and transmission routes and emphasizes the necessity for thorough compliance with good agricultural and hygienic practice at the farms to help protect the public from viral infections.

Identification and Genotyping of Human Sapoviruses Collected from Sewage Water in Naples and Palermo, Italy, in 2011

Human sapoviruses were identified in 15 (12.4 %) of 121 inlet sewage samples collected from wastewater treatment plants in Naples and Palermo, Italy, in 2011. All strains, except one GI.1, were genotyped as GI.2 by sequencing a capsid gene fragment. This is the first detection of sapovirus in wastewaters in Italy.

Hepatitis E virus in pork production chain in Czech Republic, Italy, and Spain, 2010

Processing does not substantially abate endogenous virus.

We evaluated the prevalence of hepatitis E virus (HEV) in the pork production chain in Czech Republic, Italy, and Spain during 2010. A total of 337 fecal, liver, and meat samples from animals at slaughterhouses were tested for HEV by real-time quantitative PCR. Overall, HEV was higher in Italy (53%) and Spain (39%) than in Czech Republic (7.5%). HEV was detected most frequently in feces in Italy (41%) and Spain (39%) and in liver (5%) and meat (2.5%) in Czech Republic. Of 313 sausages sampled at processing and point of sale, HEV was detected only in Spain (6%). HEV sequencing confirmed only g3 HEV strains. Indicator virus (porcine adenovirus) was ubiquitous in fecal samples and absent in liver samples and was detected in 1 slaughterhouse meat sample. At point of sale, we found porcine adenovirus in sausages (1%–2%). The possible dissemination of HEV and other fecal viruses through pork production demands containment measures.

Harmonised investigation of the occurrence of human enteric viruses in the leafy green vegetable supply chain in three European countries

Numerous outbreaks have been attributed to the consumption of raw or minimally processed leafy green vegetables contaminated with enteric viral pathogens. The aim of the present study was an integrated virological monitoring of the salad vegetables supply chain in Europe, from production, processing and point-of-sale. Samples were collected and analysed in Greece, Serbia and Poland, from 'general' and 'ad hoc' sampling points, which were perceived as critical points for virus contamination. General sampling points were identified through the analysis of background information questionnaires based on HACCP audit principles, and they were sampled during each sampling occasion where as-ad hoc sampling points were identified during food safety fact-finding visits and samples were only collected during the fact-finding visits. Human (hAdV) and porcine (pAdV) adenovirus, hepatitis A (HAV) and E (HEV) virus, norovirus GI and GII (NoV) and bovine polyomavirus (bPyV) were detected by means of real-time (RT-) PCR-based protocols. General samples were positive for hAdV, pAdV, HAV, HEV, NoV GI, NoV GII and bPyV at 20.09 % (134/667), 5.53 % (13/235), 1.32 % (4/304), 3.42 % (5/146), 2 % (6/299), 2.95 % (8/271) and 0.82 % (2/245), respectively. Ad hoc samples were positive for hAdV, pAdV, bPyV and NoV GI at 9 % (3/33), 9 % (2/22), 4.54 % (1/22) and 7.14 % (1/14), respectively. These results demonstrate the existence of viral contamination routes from human and animal sources to the salad vegetable supply chain and more specifically indicate the potential for public health risks due to the virus contamination of leafy green vegetables at primary production.

Occurrence of human enteric viruses in commercial mussels at retail level in three European countries

In this study, the prevalence of different enteric viruses in commercial mussels was evaluated at the retail level in three European countries (Finland, Greece and Spain). A total of 153 mussel samples from different origins were analysed for human norovirus (NoV) genogroups I and II, hepatitis A virus (HAV) and hepatitis E virus (HEV). Human adenovirus (HAdV) was also tested as an indicator of human faecal contamination. A full set of controls (such as sample process control, internal amplification controls, and positive and negative controls) were implemented during the process. The use of a sample process control allowed us to calculate the efficiencies of extraction, which ranged from 79 to 0.5 %, with an average value of 10 %. Samples were positive in 41 % of cases, with HAdV being the most prevalent virus detected (36 %), but no significant correlation was found between the presence of HAdV and human NoV, HAV and HEV. The prevalences of human norovirus genogroup II, HEV and human NoV genogroup I were 16, 3 and 0.7 %, respectively, and HAV was not detected. The estimated number of PCR detectable units varied between 24 and 1.4 × 10(3) g(-1) of digestive tract. Interestingly, there appeared to be a significant association between the type of mussel species (M. galloprovincialis) and the positive result of samples, although a complete overlap between country and species examined required this finding to be confirmed including samples of both species from all possible countries of origin.