Quantitative farm-to-fork human norovirus exposure assessment of individually quick frozen raspberries and raspberry puree.

A quantitative human norovirus (NoV) exposure model describing transmission of NoV during pre-harvest, harvest and further processing of soft red fruits exemplified by raspberries is presented. The outcomes of the model demonstrate the presence of NoV in raspberry puree or individual quick frozen (IQF) raspberry fruits and were generated by Monte Carlo simulations by combining GoldSim® and @Risk® software. Input data were collected from scientific literature, observational studies and assumptions. NoV contamination of soft red fruits is assumed to take place at farms by application of contaminated water for pesticides dilution or by berries' pickers shedding NoV. The model was built simulating that a collection center received berries from ten farms with a total of 245 food handlers picking soft red fruits during a 10-hour day shift. Given 0, 5 and 20 out of 245 berries' pickers were shedding NoV, these conditions were calculated to result in a mean NoV contamination of respectively 0.47, 14.1 and 36.2 NoV particles per kg raspberries in case all raspberries are mixed to one day-batch of 11tons. The NoV contamination of the fruits was mainly driven by the route of NoV shedding food pickers (95.8%) rather than by spraying contaminated pesticide water (4.2%) (baseline scenario with 5 shedding pickers and contaminated pesticide water). Inclusion of appropriate hand washing procedures or hand washing followed by hand disinfection resulted in estimated reductions of the mean NoV levels from 14.1 to 0.16 and 0.17 NoV particles per kg raspberries, respectively, for the baseline scenario with 5 out of 245 food pickers shedding NoV. The use of a mild heat treatment (30s at 75°C) during further processing of berries to purees was noted to reduce mean NoV levels substantially from 14.1 to 0.2 NoV particles per kg raspberry puree. For IQF raspberries, the NoV contamination is heterogeneously distributed and resulted in a mean contamination of 3.1 NoV particles per 250g package containing approximately 115 berries. This farm-to-fork model is a useful tool for evaluating NoV mitigation strategies in the soft red fruit supply chain.

Efficacy of electrolyzed oxidizing water and lactic acid on the reduction of Campylobacter on naturally contaminated broiler carcasses during processing.

Campylobacter is the most commonly reported gastrointestinal bacterial pathogen in humans in many developed countries. During slaughter of broiler flocks, it is difficult to avoid contamination of broiler carcasses. This study aimed to quantify Campylobacter contamination on broiler carcasses at 5 points in the slaughter processing during the slaughter of a Campylobacter-colonized flock by real-time PCR and conventional enumeration. In addition, the decontamination effect of neutral electrolyzed oxidizing (EO) water and 1.5% lactic acid (pH 2.0) were evaluated. During processing, the Campylobacter counts on the carcasses declined toward the end of the processing line. The log counts on the carcasses as determined by quantitative real-time PCR (qPCR), decreased from 9.37 after scalding to 8.08 after the last cooling step. Enumeration of the campylobacters on plates revealed the same trend, although the counts per carcass were generally 3 logs lower. After scalding, a mean of 6.86 log cfu/carcass were counted, which decreased to 4.83 log cfu/carcass after the last cooling step. Submerging carcasses after scalding in EO water gave a significant reduction of 1.31 log cfu/carcass by enumeration on plates and a not significant reduction of 0.53 log cfu/carcass by qPCR. Treatment of the carcasses after the inside-outside bird washer led to reductions from 0.09 to 0.91 log cfu/carcass, although not significant. After submerging the carcasses in a 1.5% lactic acid solution, significant reductions of 1.62 and 1.24 log cfu/carcass by qPCR and enumeration, respectively, were observed. Spraying the carcasses with lactic acid led to nonsignificant reductions of 0.68 log cfu/carcass determined by qPCR and 0.26 log cfu/carcass by enumeration. Both EO water and lactic acid seem promising for implementation in poultry processing plants.

Review: norovirus prevalence in Belgian, Canadian and French fresh produce: a threat to human health?

Foodborne viruses, especially noroviruses (NoV), are increasingly reported as the cause of foodborne outbreaks. NoV outbreaks have been reported linked to fresh soft red fruits and leafy greens. Belgium, Canada and France were the first countries to provide data about the prevalence of NoV on fresh produce. In total, 867 samples of leafy greens, 180 samples of fresh soft red fruits and 57 samples of other types of fresh produce (tomatoes, cucumber and fruit salads) were analyzed. Firstly, the NoV detection methodology, including virus and RNA extraction, real-time RT-PCR and quality controls were compared among the three countries. In addition, confirmation and genotyping of the NoV strains was attempted for a subset of NoV positive samples using conventional RT-PCR targeting an alternative region followed by sequencing. Analysis of the process control showed that 653, 179 and 18 samples of the leafy greens, soft red fruits and other fresh produce types were valid for analysis based on the recovery of the process control. NoV was detected by real-time RT-PCR in 28.2% (N=641), 33.3% (N=6) and 50% (N=6) of leafy greens tested in Canada, Belgium and France, respectively. Soft red fruits were found positive by real-time RT-PCR in 34.5% (N=29) and 6.7% (N=150) of the samples tested in Belgium and France, respectively. 55.5% (N=18) of the other fresh produce types, analyzed in Belgium, were found NoV positive by real-time RT-PCR. Conventional RT-PCR resulted in an amplicon of the expected size in 19.5% (52/266) of the NoV positive samples where this assay was attempted. Subsequent sequencing was only successful in 34.6% (18/52) of the suspected amplicons obtained by conventional RT-PCR. From this study, using the described methodology, NoV genomes were frequently detected in fresh produce however sequence confirmation was not successful for the majority of the samples tested. Infection or outbreaks were rarely or not known to be related to the NoV positive samples. With the increase in sensitivity of the detection methodology, there is an increasing concern about the interpretation of positive NoV results by real-time amplification. Strategies to confirm the results by real-time RT-PCR should be developed in analogy with the detection of microbial pathogens in foods. Detection might indicate contact with NoV in the fresh produce chain. Consequently, a potential risk for infection cannot be excluded but the actual risk from RT-PCR NoV positive produce is still unknown. Studies should be designed determining the probability of infection related to the presence or levels of NoV genomic copies.

Reported foodborne outbreaks due to noroviruses in Belgium: the link between food and patient investigations in an international context.

The Belgian data for foodborne norovirus (NoV) outbreaks became available for the first time with the introduction of an extraction and detection protocol for NoV in the National Reference Laboratory for foodborne outbreaks in September 2006. In 2007, 10 NoV foodborne outbreaks were reported affecting 392 persons in Belgium. NoV became the most detected agent in foodborne outbreaks followed by Salmonella (eight foodborne outbreaks). The major implicated foods were sandwiches (4/10), where food handlers reported a history of gastroenteritis in two outbreaks. A food handler was implicated in the limited number of Belgian NoV outbreaks which is in accord with internationally recorded data. Forty foodborne and waterborne outbreak events due to NoV, epidemiological and/or laboratory confirmed, from 2000 to 2007 revealed that in 42.5% of the cases the food handler was responsible for the outbreak, followed by water (27.5%), bivalve shellfish (17.5%) and raspberries (10.0%).