Farm biosecurity measures to prevent hepatitis E virus infection in finishing pigs on endemically infected pig farms

Hepatitis E virus (HEV) can be transmitted from pigs to humans and cause liver inflammation. Pigs are a major reservoir of HEV and most slaughter pigs show evidence of infection by presence of antibodies (ELISA) or viral RNA (PCR). Reducing the number of HEV infected pigs at slaughter would likely reduce human exposure, yet how this can be achieved, is unknown. We aimed to identify and quantify the effect of biosecurity measures to deliver HEV negative batches of pigs to slaughter. A case-control study was performed with Dutch pig farms selected based on results of multiple slaughter batches. Case farms delivered at least one PCR and ELISA negative batch to slaughter (PCR^-ELISA^-), indicating absence of HEV infection, and control farms had the highest proportion of PCR and/or ELISA positive batches (PCR⁺ELISA⁺), indicating high within-farm transmission. Data about biosecurity and housing were collected via a questionnaire and an audit. Variables were selected by regularization (LASSO regression) and ranked, based the frequency of variable selection. The odds ratios (OR) for the relation between case-control status and the highest ranked variables were determined via grouped logistic regression. Thirty-five case farms, with 10 to 60% PCR^-ELISA^- batches, and 38 control farms with on average 40% PCR⁺ELISA⁺ batches, were included. Rubber and steel floor material in fattening pens had the highest ranking and increased the odds of a PCR^-ELISA^- batch by 5.87 (95%CI 3.03-11.6) and 7.13 (95%CI 3.05-16.9) respectively. Cleaning pig driving boards weekly (OR 1.99 (95%CI 1.07-3.80)), and fly control with predatory flies (OR 4.52 (95%CI 1.59-13.5)) were protective, whereas a long fattening period was a risk. This study shows that cleaning and cleanability of floors and fomites and adequate fly control are measures to consider for HEV control in infected farms. Yet, intervention studies are needed to confirm the robustness of these outcomes.

A Comprehensive Sampling Study on SARS-CoV-2 Contamination of Air and Surfaces in a Large Meat Processing Plant Experiencing COVID-19 Clusters in June 2020

OBJECTIVE

We aimed to assess SARS-CoV-2 contamination of air and surfaces to gain insight into potential occupational exposure in a large meat processing plant experiencing COVID-19 clusters. Methods: Oro-nasopharyngeal SARS-CoV-2 screening was performed in 76 workers. Environmental samples ( n = 275) including air, ventilation systems, sewage, and swabs of high-touch surfaces and workers' hands were tested for SARS-CoV-2 RNA by real-time quantitative polymerase chain reaction. Results: Twenty-seven (35.5%) of the (predominantly asymptomatic) workers tested positive with modest to low viral loads (cycle threshold ≥ 29.7). Six of 203 surface swabs, 1 of 12 personal air samples, and one of four sewage samples tested positive; other samples tested negative. Conclusions: Although one third of workers tested positive, environmental contamination was limited. Widespread SARS-CoV-2 transmission via air and surfaces was considered unlikely within this plant at the time of investigation while strict COVID-19 control measures were already implemented.

Associations of carcass weight and trimming loss with cull dairy cow health observations collected at slaughter

Cull dairy cows account for around 27 percent of total head EU beef and veal production. For the Netherlands specific, even 42 percent (European Commission, 2022). As they are primarily kept to produce milk, red meat production is an additional source of revenue for dairy farmers. Insights in postmortem health observations that are not always visible on the living animal such as heart or liver issues, bruises, adhesions and injuries on the locomotor system, may contain valuable information for farmers to increase revenue and reduce losses in red meat production from cull dairy cows. Our goal was to obtain insights in the association of postmortem health observations with carcass weight and trimming losses. Data of 592,268 slaughter cows were available for analysis and models were built to explain carcass and trimming loss by the postmortem health observations. Carcass weight is lower for younger cows (-3.2 to -84.9 kg), cows with multiple health observations (-7.4 to -34.3 kg) and specific observations for the locomotor system (-16.7 to -22.7 kg), back (-17.9 kg), hindquarter (-21.6 kg) and chest and ribs (-15.5 to -27.6 kg). Total number of health observations (+2.0 to +6.5 kg), observations on the locomotor system (+3.3 to +5.4 kg) and on the chest and ribs (+2.2 to +9.8 kg) were the main predictors for trimming loss. Carcass weight is more affected by systemic health issues and diseases prior to slaughter leading to a negative energy balance and consequently reduced carcass weight. Trimming loss is more a consequence of the focus on meat quality and food safety in the slaughter process. Better understanding of the effect of on-farm management, on health, carcass weight and trimming loss will provide new insights for farmers and veterinarians but will also give them more action perspective to improve dairy farm preventive management and reduce losses at slaughter.

Experimental and field investigations of exposure, replication and transmission of SARS-CoV-2 in pigs in the Netherlands

In order to assess the risk of SARS-CoV-2 infection, transmission and reservoir development in swine, we combined results of an experimental and two observational studies. First, intranasal and intratracheal challenge of eight pigs did not result in infection, based on clinical signs and PCR on swab and lung tissue samples. Two serum samples returned a low positive result in virus neutralization, in line with findings in other infection experiments in pigs. Next, a retrospective observational study was performed in the Netherlands in the spring of 2020. Serum samples (N =417) obtained at slaughter from 17 farms located in a region with a high human case incidence in the first wave of the pandemic. Samples were tested with protein micro array, plaque reduction neutralization test and receptor-binding-domain ELISA. None of the serum samples was positive in all three assays, although six samples from one farm returned a low positive result in PRNT (titers 40-80). Therefore we conclude that serological evidence for large scale transmission was not observed. Finally, an outbreak of respiratory disease in pigs on one farm, coinciding with recent exposure to SARS-CoV-2 infected animal caretakers, was investigated. Tonsil swabs and paired serum samples were tested. No evidence for infection with SARS-CoV-2 was found. In conclusion, Although in both the experimental and the observational study few samples returned low antibody titer results in PRNT infection with SARS-CoV-2 was not confirmed. It was concluded that sporadic infections in the field cannot be excluded, but large-scale SARS-CoV-2 transmission among pigs is unlikely.

Effectiveness and costs of interventions to reduce the within-farm Toxoplasma gondii seroprevalence on pig farms in the Netherlands

BACKGROUND

The parasite Toxoplasma gondii (T. gondii) is recognized as one of the major foodborne pathogens with a high human disease burden. To control T. gondii infections in pigs, European Food Safety Agency (EFSA) advises serological testing of pigs and audits of pig farms to identify risk factors for T. gondii infection. In line with this approach, the aim of the current study was to assess the effectiveness and costs of intervention measures implemented to reduce the T. gondii seroprevalence on finishing pig farms in the Netherlands. A crossover clinical trial was conducted at five case farms were their own control and the cross-over moment was the implementation of interventions to reduce risk factors. Each of the case farms had a farm-specific intervention strategy with one principal intervention measure (neutering of cats, professional rodent control or covering food storage).

RESULTS

All finishing pig farms (n = 5) showed a reduction in T. gondii seroprevalence within one year of implementing the intervention strategy. Cat neutering (n = 3) and feed coverage (n = 1) showed statistically significant reductions in seroprevalence. Rodent control (n = 1) did not show a statistically significant reduction. The estimated reduction in seroprevalence in response to the neutering of cats and feed coverage were 67 and 96 %, respectively.

CONCLUSIONS

Our work demonstrates that it is possible to reduce the within-farm T. gondii seroprevalence within one year after interventions were implemented to reduce T. gondii risk factors. This information is essential and encouraging for policy makers, food business operators, and farmers to implement in their risk assessment and to apply to food safety control systems.

Added Value of Meat Inspection Data for Monitoring of Dairy Cattle Health in the Netherlands

Meat inspection records of one large cattle slaughterhouse were analyzed to evaluate the added value of slaughterhouse data for cattle health surveillance in the Netherlands. Data were available from January 2015 to September 2018, consisting of 467,361 meat inspection records. Analyses included (1) an assessment of the representativeness of the cattle herds in the slaughterhouse data in relation to the cattle herd population in the Netherlands, and (2) multivariable analyses to quantify associations between meat inspection findings and farm of origin characteristics, and the trends in time of the findings in slaughtered cattle. Ninety percent of the meat inspection records originated from dairy cattle therefore this paper only presents the results of dairy herds (N = 422,194 cattle). The dairy herds in the slaughterhouse data seemed representative for the Dutch dairy population although their regional coverage differed from the distribution of dairy herds in the Netherlands. Non-dairy herds were underrepresented in the slaughterhouse data which stresses the importance of the inclusion of data from other slaughterhouses that may be more specialized in slaughtering beef cattle. Inspection records were categorized into 15 indicators related to ante-mortem and post-mortem findings. Following multivariable analyses, seven indicators were deemed of added value to existing cattle health surveillance components, as they provided either new information or information regarding specific health problems.

Infection dynamics and persistence of hepatitis E virus on pig farms - a review

Background

Hepatitis E virus (HEV) genotype 3 and 4 is a zoonosis that causes hepatitis in humans. Humans can become infected by consumption of pork or contact with pigs. Pigs are the main reservoir of the virus worldwide and the virus is present on most pig farms.

Main body

Though HEV is present on most farms, the proportion of infected pigs at slaughter and thus the level of exposure to consumers differs between farms and countries. Understanding the cause of that difference is necessary to install effective measures to lower HEV in pigs at slaughter. Here, HEV studies are reviewed that include infection dynamics of HEV in pigs and on farms, risk factors for HEV farm prevalence, and that describe mechanisms and sources that could generate persistence on farms. Most pigs become infected after maternal immunity has waned, at the end of the nursing or beginning of the fattening phase. Risk factors increasing the likelihood of a high farm prevalence or proportion of actively infected slaughter pigs comprise of factors such as farm demographics, internal and external biosecurity and immunomodulating coinfections. On-farm persistence of HEV is plausible, because of a high transmission rate and a constant influx of susceptible pigs. Environmental sources of HEV that enhance persistence are contaminated manure storages, water and fomites.

Conclusion

As HEV is persistently present on most pig farms, current risk mitigation should focus on lowering transmission within farms, especially between farm compartments. Yet, one should be aware of the paradox of increasing the proportion of actively infected pigs at slaughter by reducing transmission insufficiently. Vaccination of pigs may aid HEV control in the future.

Occupational Exposure and Carriage of Antimicrobial Resistance Genes (tetW, ermB) in Pig Slaughterhouse Workers

Objectives

Slaughterhouse staff is occupationally exposed to antimicrobial resistant bacteria. Studies reported high antimicrobial resistance gene (ARG) abundances in slaughter pigs. This cross-sectional study investigated occupational exposure to tetracycline (tetW) and macrolide (ermB) resistance genes and assessed determinants for faecal tetW and ermB carriage among pig slaughterhouse workers.

Methods

During 2015–2016, 483 faecal samples and personal questionnaires were collected from workers in a Dutch pig abattoir, together with 60 pig faecal samples. Human dermal and respiratory exposure was assessed by examining 198 carcass, 326 gloves, and 33 air samples along the line, next to 198 packed pork chops to indicate potential consumer exposure. Samples were analyzed by qPCR (tetW, ermB). A job exposure matrix was created by calculating the percentage of tetW and ermB positive carcasses or gloves for each job position. Multiple linear regression models were used to link exposure to tetW and ermB carriage.

Results

Workers are exposed to tetracycline and macrolide resistance genes along the slaughter line. Tetw and ermB gradients were found for carcasses, gloves, and air filters. One packed pork chop contained tetW, ermB was non-detectable. Human faecal tetW and ermB concentrations were lower than in pig faeces. Associations were found between occupational tetW exposure and human faecal tetW carriage, yet, not after model adjustments. Sampling round, nationality, and smoking were determinants for ARG carriage.

Conclusion

We demonstrated clear environmental tetracycline and macrolide resistance gene exposure gradients along the slaughter line. No robust link was found between ARG exposure and human faecal ARG carriage.

Description and determinants of the faecal resistome and microbiome of farmers and slaughterhouse workers: A metagenome-wide cross-sectional study

BACKGROUND

By studying the entire human faecal resistome and associated microbiome, the diversity and abundance of faecal antimicrobial resistance genes (ARGs) can be comprehensively characterized. Prior culture-based studies have shown associations between occupational exposure to livestock and carriage of specific antimicrobial resistant bacteria. Using shotgun metagenomics, the present study investigated 194 faecal resistomes and bacteriomes from humans occupationally exposed to ARGs in livestock (i.e. pig and poultry farmers, employees and family members and pig slaughterhouse workers) and a control population (Lifelines cohort) in the Netherlands. In addition, we sought to identify determinants for the human resistome and bacteriome composition by applying a combination of multivariate (NMDS, PERMANOVA, SIMPER and DESeq2 analysis) and multivariable regression analysis techniques.

RESULTS

Pig slaughterhouse workers and pig farmers carried higher total ARG abundances in their stools compared to broiler farmers and control subjects. Tetracycline, β-lactam and macrolide resistance gene clusters dominated the resistome of all studied groups. No significant resistome alpha diversity differences were found among the four populations. However, the resistome beta diversity showed a separation of the mean resistome composition of pig and pork exposed workers from broiler farmers and controls, independent of their antimicrobial use. We demonstrated differences in resistome composition between slaughter line positions, pig versus poultry exposed workers, as well as differences between farmers and employees versus family members. In addition, we found a significant correlation between the bacteriome and resistome, and significant differences in the bacteriome composition between and within the studied subpopulations. Finally, an in-depth analysis of pig and poultry farms - of which also farm livestock resistomes were analysed - showed positive associations between the number of on-farm working hours and human faecal AMR loads.

CONCLUSION

We found that the total normalized faecal ARG carriage was larger in persons working in the Dutch pork production chain compared to poultry farmers and controls. Additionally, we showed significant differences in resistome and bacteriome composition of pig and pork exposed workers compared to a control group, as well as within-population (farms, slaughterhouse) compositional differences. The number of on-farm working hours and the farm type (pig or broiler) that persons live or work on are determinants for the human faecal resistome. Overall, our results may suggest direct or indirect livestock contact as a determinant for human ARG carriage. Future studies should further focus on the connection between the human and livestock resistome (i.e. transmission routes) to substantiate the evidence for livestock-associated resistome acquisition.

Behavioural factors of Dutch pig producers related to control of toxoplasma gondii infections in pigs

Toxoplasma gondii (T. gondii) is a food safety hazard which causes a substantial human disease burden. Infected pig meat is a common risk source of toxoplasmosis. Therefore, it is important to control T. gondii infections in pigs. Improving farm management to control the introduction risk likely contributes to that aim. A pig producer only implements control measures when he or she is aware of the underlying problem, wants to solve it, and is able to solve it. If a pig producer is not implementing appropriate control measures, behavioural change interventions can be introduced to overcome constraining behavioural factors. To aid in designing behaviour change interventions, this study analysed behavioural factors of Dutch pig producers in terms of capability, opportunity and motivation to control T. gondii infections in pigs. Key risk sources analysed focused on the life cycle of T. gondii, with cats as primary host, rodents as intermediate host, and uncovered feed as an important risk source. A survey was conducted among Dutch pig producers. Responses were analysed using descriptive and cluster analysis. Results showed that around 80% of the 67 responding pig producers was aware of key risk sources of T. gondii infections in pigs. Respondents also rated risk sources that are not known to increase the risk of T. gondii infections in pigs as somewhat important. Many respondents did not know about potential consequences of a T. gondii infection in pigs on human health. Two third expected some impact on pig performance, which is incorrect because T. gondii generally does not make pigs ill. Most respondents indicated to have the motivation and opportunity to control the risk sources cats, rodents and uncovered feed. Three pig producer clusters were identified: one with higher capability to control rodents, one with lower motivation to control rodents and cats and to cover feed storages, and one with lower scores on the importance of rodent control for pigs, human health and farm profit. We conclude that, although many pig producers have knowledge about risk sources for and consequences of T. gondii infections in pigs, the public health impact and risks of T. gondii infections in pigs are not yet common knowledge among all Dutch pig producers. Furthermore, Dutch pig producers differ in opportunity and motivation to control T. gondii infections. Targeted interventions to address these specific constraining behavioural factors can help to improve the control of T. gondii infections in pigs.

Large-scale serological screening of slaughter pigs for Toxoplasma gondii infections in The Netherlands during five years (2012-2016): Trends in seroprevalence over years, seasons, regions and farming systems

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The seroprevalence of T. gondii in slaughter pigs was between 1.4% and 2.8%.

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The seroprevalence of T. gondii in slaughter pigs showed a peak in winter.

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Pigs from organic farms had a higher seroprevalence of T. gondii.

Toxoplasma gondii is the causative agent of the parasitic disease toxoplasmosis, which is an important foodborne zoonosis. Eating undercooked meat of infected animals, including pigs, has been considered the major transmission route of T. gondii to humans. Therefore, it is urgent to develop and implement intervention measures in the pork meat chain to reduce risks of acquiring a T. gondii infection. Proposed measures for control of T. gondii in pigs include serological testing of pigs and audits of pig farms on risk factors for T. gondii infection. So far, these ideas have not been tested in practice. In order to generate knowledge about the epidemiology and seroprevalence of T. gondii, as a basis for developing a surveillance system, we studied the long term seroprevalence over years, farming systems and regions, and seasonal patterns of T. gondii seroprevalence in Dutch slaughter pigs. During a five year study period from 2012 to 2016, serum samples were routinely collected in five Dutch pig slaughterhouses. The sera were tested in an ELISA for the presence of antibodies against Toxoplasma. In total 226,340 serum samples were collected and tested during the study period. The observed seroprevalence varied over years, with the highest overall seroprevalence in 2014 (2.8%) and the lowest in 2016 (1.4%). A higher seroprevalence was observed in pigs from organic farms compared to pigs from conventional farms. The overall risk of infection was on average 2.63 times significantly (p < 0.001) higher for organically raised pigs than for conventionally raised pigs. A seasonal pattern in seroprevalence was observed: the results showed a dominant annual periodicity with a seroprevalence peak in winter around week 1 and a minimum seroprevalence in summer around week 27.

To our knowledge, this is the first large scale study on the seroprevalence of T. gondii in slaughter pigs. In comparison to other European serological studies, the observed seroprevalence seems to be relatively low. However, care is needed when comparing the results with other studies because of differences in test setup, the number of samples and time period of sampling. The results can be used as a starting point for developing a surveillance system for T. gondii, and for implementation of intervention measures.

Prioritisation of food-borne parasites in Europe, 2016

Background and aimsPriority setting is a challenging task for public health professionals. To support health professionals with this and in following a recommendation from the Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO), 35 European parasitologists attended a workshop from 8-12 February 2016 to rank food-borne parasites (FBP) in terms of their importance for Europe and regions within Europe. Methods: Countries were divided into European regions according to those used by the European Society of Clinical Microbiology and Infectious Diseases. We used the same multicriteria decision analysis approach as the FAO/WHO, for comparison of results, and a modified version, for better regional representation. Twenty-five FBP were scored in subgroups, using predefined decision rules. Results: At the European level, Echinococcus multilocularis ranked first, followed by Toxoplasma gondii and Trichinella spiralis. At the regional level, E. multilocularis ranked highest in Northern and Eastern Europe, E. granulosus in South-Western and South-Eastern Europe, and T. gondii in Western Europe. Anisakidae, ranking 17th globally, appeared in each European region's top 10. In contrast, Taenia solium, ranked highest globally but 10th for Europe. Conclusions: FBP of importance in Europe differ from those of importance globally, requiring targeted surveillance systems, intervention measures, and preparedness planning that differ across the world and across Europe.

Knowledge gaps and research priorities in the prevention and control of hepatitis E virus infection

Hepatitis E virus (HEV), family Hepeviridae, is a main cause of epidemic hepatitis in developing countries and sporadic and cluster cases of hepatitis in industrialized countries. There are an increasing number of reported cases in humans especially in industrialized countries, and there is a high potential for transboundary spread of zoonotic genotypes of the virus through the transport of pigs, pig products and by-products. Bloodborne transmission of the virus has been reported with a significant medical concern. To better coordinate HEV research and design better control measures of HEV infections in animals, a group of HEV experts reviewed the current knowledge on the disease and considered the existing disease control tools. It was concluded that there is a lack of in-depth information about the spread of the virus from pigs to humans. The role of animals other than pigs in the zoonotic transmission of the virus to humans and the extent of foodborne transmission are poorly understood. Factors involved in development of clinical disease such as infectious dose, susceptibility and virulence of virus strains need to be studied more extensively. However, such studies are greatly hindered by the absence of a broadly applicable, efficient and sensitive in vitro cell culture system for HEV. Diagnostic tools for HEV are available but need to be further validated, harmonized and standardized. Commercially available HEV vaccines for the control of HEV infection in animal populations are needed as such vaccines can minimize the zoonotic risk for humans. Anti-HEV drugs for treatment of HEV-infected patients need to be studied more extensively. The detailed expert review can be downloaded from the project website at http://www.discontools.eu/.

The economic burden of a Salmonella Thompson outbreak caused by smoked salmon in the Netherlands, 2012-2013

Background

In 2012, the Netherlands experienced the most extensive food-related outbreak of Salmonella ever recorded. It was caused by smoked salmon contaminated with Salmonella Thompson during processing. In total, 1149 cases of salmonellosis were laboratory confirmed and reported to RIVM. Twenty percent of cases was hospitalised and four cases were reported to be fatal. The purpose of this study was to estimate total costs of the Salmonella Thompson outbreak.

Methods

Data from a case-control study were used to estimate the cost-of-illness of reported cases (i.e. healthcare costs, patient costs and production losses). Outbreak control costs were estimated based on interviews with staff from health authorities. Using the Dutch foodborne disease burden and cost-of-illness model, we estimated the number of underestimated cases and the associated cost-of-illness.

Results

The estimated number of cases, including reported and underestimated cases was 21 123. Adjusted for underestimation, the total cost-of-illness would be €6.8 million (95% CI €2.5-€16.7 million) with productivity losses being the main cost driver. Adding outbreak control costs, the total outbreak costs are estimated at €7.5 million.

Conclusion

In the Netherlands, measures are taken to reduce salmonella concentrations in food, but detection of contamination during food processing remains difficult. As shown, Salmonella outbreaks have the potential for a relatively high disease and economic burden for society. Early warning and close cooperation between the industry, health authorities and laboratories is essential for rapid detection, control of outbreaks, and to reduce disease and economic burden.

A summary index for antimicrobial resistance in food animals in the Netherlands

BACKGROUND

The Dutch government has set targets for reduction of antimicrobial usage in food animals, stipulating a 50% reduction in usage (on a weight basis) in 2013 as compared to 2009 and a 70% decrease in 2015. A monitoring program has been instituted to evaluate the impact on antimicrobial resistance (AMR). The Dutch Ministry of Public Health Welfare and Sports has expressed the need for a summary index to present the results of the monitoring data concisely to policy makers.

METHODS

We use data on AMR in bacteria from randomly collected samples from broiler chickens, fattening pigs, veal calves and dairy cows. Escherichia coli was selected for resistance monitoring because they are intrinsically susceptible to the antibiotics included in the test panel (ciprofloxacin, cefotaxime, tetracycline and ampicillin) and they are present in all samples, which facilitates proper randomization and trend analysis. The AMR summary index was calculated for each animal species as a weighted average over the four antibiotics, taking into account their clinical relevance. Weights were obtained by conjoint analysis, a pairwise comparison study involving infectious diseases professionals with clinical and public health backgrounds, with data analysis by conditional logistic regression. The AMR summary index was then computed by Monte Carlo simulation, accounting for sampling and regression uncertainty.

RESULTS

The highest weights (0.35) were given to ciprofloxacin and cefotaxime followed by ampicillin (0.23) and tetracycline (0.07). Throughout the years, the AMR index was highest in broiler chickens, followed by pigs and veal calves, while the lowest values were consistently recorded in dairy cows. In all animal species, the index in 2014 was significantly lower than in 2009.

CONCLUSIONS

We demonstrate that high-dimensional data on surveillance of antimicrobial resistance can be summarized in an index for evaluating trends between and within food animal species by a process involving decision makers and scientists to select and weight the most relevant antibiotics.

Risk ranking of foodborne parasites: State of the art

In a time of increasing threats and decreasing financial resources, monitoring and controlling all possible foodborne hazards at the same time and to the same extent has become more challenging than ever. Therefore, attention is increasingly being paid to the so-called "risk ranking" methods that enable decision makers to focus on the most important foodborne hazards - even when time is limited and knowledge incomplete. In this review paper, we provide an overview of the most common quantitative methods and metrics used for ranking the risks associated with foodborne parasites and present the state of the art on risk ranking exercises for foodborne parasites. A number of risk ranking metrics and methods are available, ranging from simple approaches that can be used to assess the health or economic impact of a foodborne parasitic disease, to more complicated but more comprehensive multi-criteria assessments. For health impact assessment, measures of population health such as disease occurrence and number of deaths; Disability-Adjusted Life Years (DALYs) measuring the healthy life years lost; and Quality-Adjusted Life Years (QALYs) measuring the number of life years lived in optimal health, are described. For economic impact assessment, applied approaches that measure the cost-of-illness from a societal perspective and stated preference methods are outlined. Finally, Multi-Criteria Decision Analysis (MCDA), which can be used to integrate multiple metrics and criteria into a single ranking, is described. These risk ranking methods for foodborne parasites are increasingly performed to aid priority setting at global, regional, and national levels. As different stakeholders have their own prioritization objectives and beliefs, the outcome of such exercises is necessarily context-dependent. Therefore, when designing a risk ranking exercise for foodborne parasites, it is important to choose the metrics and methods, as well as what to rank, in the light of the predefined context of the question being addressed and the target audience.

Virological Quality of Irrigation Water in Leafy Green Vegetables and Berry Fruits Production Chains

This study condenses data acquired during investigations of the virological quality of irrigation water used in production of fresh produce. One hundred and eight samples of irrigation water were collected from five berry fruit farms in Finland (1), the Czech Republic (1), Serbia (2), and Poland (1), and sixty-one samples were collected from three leafy green vegetable farms in Poland, Serbia, and Greece. Samples were analyzed for index viruses of human or animal fecal contamination (human and porcine adenoviruses, and bovine polyoma viruses), and human pathogenic viruses (hepatitis A virus, hepatitis E virus, and noroviruses GI/GII). Both index and pathogenic viruses were found in irrigation water samples from the leafy green vegetables production chain. The data on the presence of index viruses indicated that the highest percentage of fecal contamination was of human origin (28.1 %, 18/64), followed by that of porcine (15.4 %, 6/39) and bovine (5.1 %, 2/39) origins. Hepatitis E virus (5 %, 1/20) and noroviruses GII (14.3 %, 4/28) were also detected. Samples from berry fruit production were also positive for both index and pathogenic viruses. The highest percentage of fecal contamination was of human origin (8.3 %, 9/108), followed by that of porcine, 4.5 % (4/89) and bovine, 1.1 % (1/89) origins. Norovirus GII (3.6 %, 2/56) was also detected. These data demonstrate that irrigation water used in primary production is an important vehicle of viral contamination for fresh produce, and thus is a critical control point which should be integrated into food safety management systems for viruses. The recommendations of Codex Alimentarius, as well as regulations on the use of water of appropriate quality for irrigation purposes, should be followed.

Combining QMRA and Epidemiology to Estimate Campylobacteriosis Incidence

The disease burden of pathogens as estimated by QMRA (quantitative microbial risk assessment) and EA (epidemiological analysis) often differs considerably. This is an unsatisfactory situation for policymakers and scientists. We explored methods to obtain a unified estimate using campylobacteriosis in the Netherlands as an example, where previous work resulted in estimates of 4.9 million (QMRA) and 90,600 (EA) cases per year. Using the maximum likelihood approach and considering EA the gold standard, the QMRA model could produce the original EA estimate by adjusting mainly the dose-infection relationship. Considering QMRA the gold standard, the EA model could produce the original QMRA estimate by adjusting mainly the probability that a gastroenteritis case is caused by Campylobacter. A joint analysis of QMRA and EA data and models assuming identical outcomes, using a frequentist or Bayesian approach (using vague priors), resulted in estimates of 102,000 or 123,000 campylobacteriosis cases per year, respectively. These were close to the original EA estimate, and this will be related to the dissimilarity in data availability. The Bayesian approach further showed that attenuating the condition of equal outcomes immediately resulted in very different estimates of the number of campylobacteriosis cases per year and that using more informative priors had little effect on the results. In conclusion, EA was dominant in estimating the burden of campylobacteriosis in the Netherlands. However, it must be noted that only statistical uncertainties were taken into account here. Taking all, usually difficult to quantify, uncertainties into account might lead to a different conclusion.

Evaluation of exposure scenarios on intentional microbiological contamination in a drinking water distribution network

Drinking water distribution networks are vulnerable to accidental or intentional contamination events. The objective of this study was to investigate the effects of seeding duration and concentration, exposure pathway (ingestion via drinking of water and tooth brushing and inhalation by taking a shower) and pathogen infectivity on exposure and infection risk in the case of an intentional pathogenic contamination in a drinking water distribution network. Seeding of a pathogen for 10 min and 120 min, and subsequent spreading through a drinking water distribution network were simulated. For exposure via drinking, actual data on drinking events and volumes were used. Ingestion of a small volume of water by tooth brushing twice a day by every person in the network was assumed. Inhalation of contaminated aerosol droplets took place when taking a shower. Infection risks were estimated for pathogens with low (r = 0.0001) and high (r = 0.1) infectivity. In the served population (48 000 persons) and within 24 h, about 1400 persons were exposed to the pathogen by ingestion of water in the 10-min seeding scenario and about 3400 persons in the 120-min scenario. The numbers of exposed persons via tooth brushing were about the same as via drinking of water. Showering caused (inhalation) exposure in about 450 persons in the 10-min scenario and about 1500 in the 120-min scenario. Regardless of pathogen infectivity, if the seeding concentration is 10(6) pathogens per litre or more, infection risks are close to one. Exposure by taking a shower is of relevance if the pathogen is highly infectious via inhalation. A longer duration of the seeding of a pathogen increases the probability of exposure.

Disease Burden of 32 Infectious Diseases in the Netherlands, 2007-2011

Background

Infectious disease burden estimates provided by a composite health measure give a balanced view of the true impact of a disease on a population, allowing the relative impact of diseases that differ in severity and mortality to be monitored over time. This article presents the first national disease burden estimates for a comprehensive set of 32 infectious diseases in the Netherlands.

Methods and Findings

The average annual disease burden was computed for the period 2007–2011 for selected infectious diseases in the Netherlands using the disability-adjusted life years (DALY) measure. The pathogen- and incidence-based approach was adopted to quantify the burden due to both morbidity and premature mortality associated with all short and long-term consequences of infection. Natural history models, disease progression probabilities, disability weights, and other parameters were adapted from previous research. Annual incidence was obtained from statutory notification and other surveillance systems, which was corrected for under-ascertainment and under-reporting. The highest average annual disease burden was estimated for invasive pneumococcal disease (9444 DALYs/year; 95% uncertainty interval [UI]: 8911–9961) and influenza (8670 DALYs/year; 95% UI: 8468–8874), which represents 16% and 15% of the total burden of all 32 diseases, respectively. The remaining 30 diseases ranked by number of DALYs/year from high to low were: HIV infection, legionellosis, toxoplasmosis, chlamydia, campylobacteriosis, pertussis, tuberculosis, hepatitis C infection, Q fever, norovirus infection, salmonellosis, gonorrhoea, invasive meningococcal disease, hepatitis B infection, invasive Haemophilus influenzae infection, shigellosis, listeriosis, giardiasis, hepatitis A infection, infection with STEC O157, measles, cryptosporidiosis, syphilis, rabies, variant Creutzfeldt-Jakob disease, tetanus, mumps, rubella, diphtheria, and poliomyelitis. The very low burden for the latter five diseases can be attributed to the National Immunisation Programme. The average disease burden per individual varied from 0.2 (95% UI: 0.1–0.4) DALYs per 100 infections for giardiasis, to 5081 and 3581 (95% UI: 3540–3611) DALYs per 100 infections for rabies and variant Creutzfeldt-Jakob disease, respectively.

Conclusions

For guiding and supporting public health policy decisions regarding the prioritisation of interventions and preventive measures, estimates of disease burden and the comparison of burden between diseases can be informative. Although the collection of disease-specific parameters and estimation of incidence is a process subject to continuous improvement, the current study established a baseline for assessing the impact of future public health initiatives.

Quantitative farm-to-fork risk assessment model for norovirus and hepatitis A virus in European leafy green vegetable and berry fruit supply chains

Fresh produce that is contaminated with viruses may lead to infection and viral gastroenteritis or hepatitis when consumed raw. It is thus important to reduce virus numbers on these foods. Prevention of virus contamination in fresh produce production and processing may be more effective than treatment, as sufficient virus removal or inactivation by post-harvest treatment requires high doses that may adversely affect food quality. To date knowledge of the contribution of various potential contamination routes is lacking. A risk assessment model was developed for human norovirus, hepatitis A virus and human adenovirus in raspberry and salad vegetable supply chains to quantify contributions of potential contamination sources to the contamination of produce at retail. These models were used to estimate public health risks. Model parameterization was based on monitoring data from European supply chains and literature data. No human pathogenic viruses were found in the soft fruit supply chains; human adenovirus (hAdV) was detected, which was additionally monitored as an indicator of fecal pollution to assess the contribution of potential contamination points. Estimated risks per serving of lettuce based on the models were 3×10(-4) (6×10(-6)-5×10(-3)) for NoV infection and 3×10(-8) (7×10(-10)-3×10(-6)) for hepatitis A jaundice. The contribution to virus contamination of hand-contact was larger as compared with the contribution of irrigation, the conveyor belt or the water used for produce rinsing. In conclusion, viral contamination in the lettuce and soft fruit supply chains occurred and estimated health risks were generally low. Nevertheless, the 97.5% upper limit for the estimated NoV contamination of lettuce suggested that infection risks up to 50% per serving might occur. Our study suggests that attention to full compliance for hand hygiene will improve fresh produce safety related to virus risks most as compared to the other examined sources, given the monitoring results. This effect will be further aided by compliance with other hygiene and water quality regulations in production and processing facilities.

Cost-of-illness and disease burden of food-related pathogens in the Netherlands, 2011

To inform risk management decisions on control and prevention of food-related disease, both the disease burden expressed in Disability Adjusted Life Years (DALY) and the cost-of-illness of food-related pathogens are estimated and presented. Disease burden of fourteen pathogens that can be transmitted by food, the environment, animals and humans was previously estimated by Havelaar et al. (2012). In this paper we complement these by cost-of-illness estimates. Together, these present a complete picture of the societal burden of food-related diseases. Using incidence estimates for 2011, community-acquired non-consulting cases, patients consulting their general practitioner, hospitalized patients and the incidence of sequelae and fatal cases, estimates were obtained for DALYs, direct healthcare costs (e.g. costs for doctor's fees, hospitalizations and medicines), direct non-healthcare costs (e.g. travel costs to and from the doctor), indirect non-healthcare costs (e.g. productivity loss, special education) and total costs. The updated disease burden for 2011 was equal to 13,940 DALY/year (undiscounted) or 12,650 DALY/year (discounted at 1.5%), and was of the same magnitude as previous estimates. At the population-level thermophilic Campylobacter spp., Toxoplasma gondii and rotavirus were associated with the highest disease burden. Perinatal listeriosis infection was associated with the highest DALY per symptomatic case. The total cost-of-illness in 2011 of fourteen food-related pathogens and associated sequelae was estimated at € 468 million/year, if undiscounted, and at € 416 million/year if discounted by 4%. Direct healthcare costs accounted for 24% of total costs, direct non-healthcare costs for 2% and indirect non-healthcare costs for 74% of total costs. At the population-level, norovirus had the highest total cost-of-illness in 2011 with € 106 million/year, followed by thermophilic Campylobacter spp. (€ 76 million/year) and rotavirus (€ 73 million/year). Cost-of-illness per infected case varied from € 150 for Clostridium perfringens intoxications to € 275,000 for perinatal listeriosis. Both incident cases and fatal cases are more strongly correlated with COI/year than with DALY/year. More than 40% of all cost-of-illness and DALYs can be attributed to food, in total € 168 million/year and 5,150 DALY/year for 2011. Beef, lamb, pork and poultry meat alone accounted for 39% of these costs. Products of animal origin accounted for € 86 million/year (or 51% of the costs attributed to food) and 3,320 DALY/year (or 64% of the disease burden attributed to food). Among the pathogens studied Staphylococcus aureus intoxications accounted for the highest share of costs attributed to food (€ 47.1 million/year), followed by Campylobacter spp. (€ 32.0 million/year) and norovirus (€ 17.7 million/year).

Potential association between the recent increase in campylobacteriosis incidence in the Netherlands and proton-pump inhibitor use - an ecological study

The Netherlands saw an unexplained increase in campylobacteriosis incidence between 2003 and 2011, following a period of continuous decrease. We conducted an ecological study and found a statistical association between campylobacteriosis incidence and the annual number of prescriptions for proton pump inhibitors (PPIs), controlling for the patient's age, fresh and frozen chicken purchases (with or without correction for campylobacter prevalence in fresh poultry meat). The effect of PPIs was larger in the young than in the elderly. However, the counterfactual population-attributable fraction for PPIs was largest for the elderly (ca 45% in 2011) and increased at population level from 8% in 2004 to 27% in 2011. Using the regression model and updated covariate values, we predicted a trend break for 2012, largely due to a decreased number of PPI prescriptions, that was subsequently confirmed by surveillance data. Although causality was not shown, the biological mechanism, age effect and trend-break prediction suggest a substantial impact of PPI use on campylobacteriosis incidence in the Netherlands. We chose the ecological study design to pilot whether it is worthwhile to further pursue the effect of PPI on campylobacteriosis and other gastrointestinal pathogens in prospective cohort studies. We now provide strong arguments to do so.

Wipes coated with a singlet-oxygen-producing photosensitizer are effective against human influenza virus but not against norovirus

Transmission of enteric and respiratory viruses, including human norovirus (hNoV) and human influenza virus, may involve surfaces. In food preparation and health care settings, surfaces are cleaned with wipes; however, wiping may not efficiently reduce contamination or may even spread viruses, increasing a potential public health risk. The virucidal properties of wipes with a singlet-oxygen-generating immobilized photosensitizer (IPS) coating were compared to those of similar but uncoated wipes (non-IPS) and of commonly used viscose wipes. Wipes were spiked with hNoV GI.4 and GII.4, murine norovirus 1 (MNV-1), human adenovirus type 5 (hAdV-5), and influenza virus H1N1 to study viral persistence. We also determined residual and transferred virus proportions on steel carriers after successively wiping a contaminated and an uncontaminated steel carrier. On IPS wipes only, influenza viruses were promptly inactivated with a 5-log10 reduction. D values of infectious MNV-1 and hAdV-5 were 8.7 and 7.0 h on IPS wipes, 11.6 and 9.3 h on non-IPS wipes, and 10.2 and 8.2 h on viscose wipes, respectively. Independently of the type of wipe, dry cleaning removed, or drastically reduced, initial spot contamination of hNoV on surfaces. All wipes transferred hNoV to an uncontaminated carrier; however, the risk of continued transmission by reuse of wipes after 6 and 24 h was limited for all viruses. We conclude that cleaning wet spots with dry wipes efficiently reduced spot contamination on surfaces but that cross-contamination with noroviruses by wiping may result in an increased public health risk at high initial virus loads. For influenza virus, IPS wipes present an efficient one-step procedure for cleaning and disinfecting contaminated surfaces.

Viable Legionella pneumophila bacteria in natural soil and rainwater puddles

AIMS

For the majority of sporadic Legionnaires' disease cases the source of infection remains unknown. Infection may possible result from exposure to Legionella bacteria in sources that are not yet considered in outbreak investigations. Therefore, potential sources of pathogenic Legionella bacteria--natural soil and rainwater puddles on roads--were studied in 2012.

METHODS AND RESULTS

Legionella bacteria were detected in 30% (6/20) of soils and 3·9% (3/77) of rainwater puddles by amoebal coculture. Legionella pneumophila was isolated from two out of six Legionella positive soil samples and two out of three Legionella positive rainwater samples. Several other species were found including the pathogenic Leg. gormanii and Leg. longbeachae. Sequence types (ST) could be assigned to two Leg. pneumophila strains isolated from soil, ST710 and ST477, and one strain isolated from rainwater, ST1064. These sequence types were previously associated with Legionnaires' disease patients.

CONCLUSIONS

Rainwater and soil may be alternative sources for Legionella.

SIGNIFICANCE AND IMPACT OF THE STUDY

The detection of clinically relevant strains indicates that rainwater and soil are potential sources of Legionella bacteria and future research should assess the public health implication of the presence of Leg. pneumophila in rainwater puddles and natural soil.

Health risk assessment for splash parks that use rainwater as source water

In the Netherlands, rainwater becomes more and more popular as an economic and environmentally sustainable water source for splash parks, however, the associated public health risk and underlying risk factors are unknown. Since splash parks have been associated with outbreaks of infectious diseases, a quantitative microbial risk assessment was performed using Legionella pneumophila as a target pathogen to quantify the risk of infection for exposure due to inhalation and Campylobacter jejuni for ingestion. Data for L. pneumophila and C. jejuni concentrations in rainfall generated surface runoff from streets were extracted from literature. Data for exposure were obtained by observing 604 people at splash parks, of whom 259 were children. Exposure volumes were estimated using data from literature to determine the volume of exposure through inhalation at 0.394 μL/min (95% CI-range 0.0446-1.27 μL/min), hand-to-mouth contact at 22.6 μL/min, (95% CI-range 2.02-81.0 μL/min), ingestion of water droplets at 94.4 μL/min (95% CI-range 5.1-279 μL/min) and ingestion of mouthfuls of water at 21.5·10(3) μL/min (95% CI-range 1.17 ·10(3)-67.0·10(3) μL/min). The corresponding risk of infection for the mean exposure duration of 3.5 min was 9.3·10(-5) (95% CI-range 0-2.4·10(-4)) for inhalation of L. pneumophila and 3.6·10(-2) (95% CI-range 0-5.3·10(-1)) for ingestion of C. jejuni. This study provided a methodology to quantify exposure volumes using observations on site. We estimated that using rainwater as source water for splash parks may pose a health risk, however, further detailed quantitative microbial analysis is required to confirm this finding. Furthermore we give insight into the effect of water quality standards, which may limit infection risks from exposure at splash parks.

Uncertainty of population risk estimates for pathogens based on QMRA or epidemiology: a case study of Campylobacter in the Netherlands

Epidemiology and quantitative microbiological risk assessment are disciplines in which the same public health measures are estimated, but results differ frequently. If large, these differences can confuse public health policymakers. This article aims to identify uncertainty sources that explain apparent differences in estimates for Campylobacter spp. incidence and attribution in the Netherlands, based on four previous studies (two for each discipline). An uncertainty typology was used to identify uncertainty sources and the NUSAP method was applied to characterize the uncertainty and its influence on estimates. Model outcomes were subsequently calculated for alternative scenarios that simulated very different but realistic alternatives in parameter estimates, modeling, data handling, or analysis to obtain impressions of the total uncertainty. For the epidemiological assessment, 32 uncertainty sources were identified and for QMRA 67. Definitions (e.g., of a case) and study boundaries (e.g., of the studied pathogen) were identified as important drivers for the differences between the estimates of the original studies. The range in alternatively calculated estimates usually overlapped between disciplines, showing that proper appreciation of uncertainty can explain apparent differences between the initial estimates from both disciplines. Uncertainty was not estimated in the original QMRA studies and underestimated in the epidemiological studies. We advise to give appropriate attention to uncertainty in QMRA and epidemiological studies, even if only qualitatively, so that scientists and policymakers can interpret reported outcomes more correctly. Ideally, both disciplines are joined by merging their strong respective properties, leading to unified public health measures.

Seroprevalence of hepatitis E virus in pigs from different farming systems in The Netherlands

Sporadic nontravel-related hepatitis E virus (HEV) infections have been reported in industrialized countries. These infections are caused by zoonotic HEV genotypes 3 and 4 that circulate in swine, wild boar, and deer. In The Netherlands, HEV RNA has been detected in >50% of the pig farms, and HEV-specific antibodies were detected in ∼70% of the slaughter pigs. In the current study, HEV seroprevalences were investigated in pigs raised on conventional, free-range, and organic farms in The Netherlands. Differences in seroprevalence may indicate different exposure routes or transmission dynamics within pig herds for HEV. In 2004, serum samples of 846 fattening pigs were obtained from farms that applied conventional (265 pigs at 24 farms), organic (417 pigs at 42 farms), and free-range (164 pigs at 12 farms) farming. HEV-specific antibodies were detected in samples from all conventional and free-range pig farms and in 41 of 42 organic pig farms, indicating that the probability of introducing HEV on a farm appeared to be equal for the different farming types. The estimated average within-herd seroprevalence was significantly higher for pigs raised on organic farms (89%) than for pigs raised on conventional farms (72%, P = 0.04) and nearly significant for pigs raised on free-range farms (76%, P = 0.06). Six of ten organic farms were estimated to have a withinherd seroprevalence of >95%, compared with 1 of 10 and 4 of 10 of the free-range and conventional pig farms, respectively. This suggests a higher force of infection with HEV for pigs reared on organic farms compared with pigs reared on conventional or free-range farms. This may be due to repetitive exposure to HEV caused by farming system-specific housing conditions, such as a greater contact frequency between pigs and more exposure to pig manure, increasing the transmission rate.

A decision support tool to compare waterborne and foodborne infection and/or illness risks associated with climate change

Climate change may impact waterborne and foodborne infectious disease, but to what extent is uncertain. Estimating climate-change-associated relative infection risks from exposure to viruses, bacteria, or parasites in water or food is critical for guiding adaptation measures. We present a computational tool for strategic decision making that describes the behavior of pathogens using location-specific input data under current and projected climate conditions. Pathogen-pathway combinations are available for exposure to norovirus, Campylobacter, Cryptosporidium, and noncholera Vibrio species via drinking water, bathing water, oysters, or chicken fillets. Infection risk outcomes generated by the tool under current climate conditions correspond with those published in the literature. The tool demonstrates that increasing temperatures lead to increasing risks for infection with Campylobacter from consuming raw/undercooked chicken fillet and for Vibrio from water exposure. Increasing frequencies of drought generally lead to an elevated infection risk of exposure to persistent pathogens such as norovirus and Cryptosporidium, but decreasing risk of exposure to rapidly inactivating pathogens, like Campylobacter. The opposite is the case with increasing annual precipitation; an upsurge of heavy rainfall events leads to more peaks in infection risks in all cases. The interdisciplinary tool presented here can be used to guide climate change adaptation strategies focused on infectious diseases.

Virus transfer proportions between gloved fingertips, soft berries, and lettuce, and associated health risks

Multiple outbreaks of human norovirus (hNoV) have been associated with fresh produce, such as soft berries and lettuce. Even though food handlers are considered an important source for the introduction of hNoV into food chains, their contribution to public health risks associated with hNoV remains unknown. To assess to which extent food handlers contribute to the introduction and spread of hNoV in fresh produce chains quantitative virus transfer data are needed. We estimated transfer proportions of hNoV GI.4, GII.4, murine norovirus (MNV-1), a culturable surrogate of hNoV, and human adenovirus (hAdV-2), a human pathogen proposed as an indicator for human faecal pollution, between gloved fingertips and raspberries, strawberries, and lettuce, by quantitative RT-PCR and cell culture if applicable. Virus transfer proportions were corrected for virus-matrix specific recoveries, and variability and uncertainty of the parameters were estimated. Virus transfer from gloves to soft berries was generally lower as compared to lettuce, with mean transfer proportions ranging between 0.1 to 2.3% and 9 to 10% for infectious MNV-1 and hAdV-2, respectively. Transfer from produce to glove was mostly greater than transfer from glove to produce, adding to the likelihood of virus transfer due to cross contamination from contaminated produce via food handlers. HNoV GI.4 and hNoV GII.4 showed no significant difference between their mean transfer proportions. Using the estimated transfer proportions, we studied the impact of low and high transfer proportions on the public health risk, based on a scenario in which a food handler picked raspberries with contaminated fingertips. Given the made assumptions, we could show that for a pathogen as infectious as hNoV, low transfer proportions may pose a greater public health risk than high transfer proportions, due to a greater viral spread. We demonstrated the potential of food handlers in spreading hNoV in food chains, showing that prevention of virus contamination on food handlers' hands is crucial for food safety. Nevertheless, complete prevention of virus contamination on fresh produce cannot be achieved in reality, and reliable and effective intervention measures are consequently required. We estimated that, especially for low transfer proportions, a robust one log10-unit reduction of infectious hNoV on contaminated produce, and on food handlers' hands, could lower the public health risk substantially. Using the obtained data in quantitative risk assessment will aid in elucidating the contribution of food handlers in hNoV transmission.

Scoping the impact of changes in population age-structure on the future burden of foodborne disease in the Netherlands, 2020-2060

A demographic shift towards a larger proportion of elderly in the Dutch population in the coming decades might change foodborne disease incidence and mortality. In the current study we focused on the age-specific changes in the occurrence of foodborne pathogens by combining age-specific demographic forecasts for 10-year periods between 2020 and 2060 with current age-specific infection probabilities for Campylobacter spp., non-typhoidal Salmonella, hepatitis A virus, acquired Toxoplasma gondii and Listeria monocytogenes. Disease incidence rates for the former three pathogens were estimated to change marginally, because increases and decreases in specific age groups cancelled out over all ages. Estimated incidence of reported cases per 100,000 for 2060 mounted to 12 (Salmonella), 51 (Campylobacter), 1.1 (hepatitis A virus) and 2.1 (Toxoplasma). For L. monocytogenes, incidence increased by 45% from 0.41 per 100,000 in 2011 to 0.60 per 100,000. Estimated mortality rates increased two-fold for Salmonella and Campylobacter to 0.5 and 0.7 per 100,000, and increased by 25% for Listeria from 0.06 to 0.08. This straightforward scoping effort does not suggest major changes in incidence and mortality for these food borne pathogens based on changes in de population age-structure as independent factor. Other factors, such as changes in health care systems, social clustering and food processing and preparation, could not be included in the estimates.

Quantitative risk estimation for a Legionella pneumophila infection due to whirlpool use

Quantitative microbiological risk assessment was used to quantify the risk associated with the exposure to Legionella pneumophila in a whirlpool. Conceptually, air bubbles ascend to the surface, intercepting Legionella from the traversed water. At the surface the bubble bursts into dominantly noninhalable jet drops and inhalable film drops. Assuming that film drops carry half of the intercepted Legionella, a total of four (95% interval: 1-9) and 4.5×10(4) (4.4×10(4) - 4.7×10(4) ) cfu/min were estimated to be aerosolized for concentrations of 1 and 1,000 legionellas per liter, respectively. Using a dose-response model for guinea pigs to represent humans, infection risks for active whirlpool use with 100 cfu/L water for 15 minutes were 0.29 (∼0.11-0.48) for susceptible males and 0.22 (∼0.06-0.42) for susceptible females. A L. pneumophila concentration of ≥1,000 cfu/L water was estimated to nearly always cause an infection (mean: 0.95; 95% interval: 0.9-∼1). Estimated infection risks were time-dependent, ranging from 0.02 (0-0.11) for 1-minute exposures to 0.93 (0.86-0.97) for 2-hour exposures when the L. pneumophila concentration was 100 cfu/L water. Pool water in Dutch bathing establishments should contain <100 cfu Legionella/L water. This study suggests that stricter provisions might be required to assure adequate public health protection.

Reduction of bacteriophage MS2 by filtration and irradiation determined by culture and quantitative real-time RT-PCR

Molecular methods are increasingly applied for virus detection in environmental samples without rendering data on viral infectivity. Infectivity data are important for assessing public health risks from exposure to human pathogenic viruses in the environment. Here, treatment efficiencies of three (drinking) water treatment processes were estimated by quantification of the indicator virus bacteriophage MS2 with culture and real-time reverse transcription polymerase chain reaction (qRT-PCR). We studied the virus reduction by slow sand filtration at a pilot plant. No decay of MS2 RNA was observed, whereas infectious MS2 particles were inactivated at a rate of 0.1 day(-1). Removal of MS2 RNA and infectious MS2 particles was 1.2 and 1.6 log10-units, respectively. Virus reduction by UV and gamma irradiation was determined in laboratory-scale experiments. The reduction of MS2 RNA based on qRT-PCR data was negligible. Reduction of infectious MS2 particles was estimated at 3.0-3.6 log10-units (UV dose up to 400 or 800 J/m(2)) and 4.7-7 log10-units (gamma dose up to 200 Gray). As shown in this study, estimations of viral reduction, both inactivation and removal, obtained by molecular methods should be interpreted carefully when considering treatment options to provide virus-safe drinking water. Combining culture-based methods with molecular methods may provide supplementary information on mechanisms of virus reduction.

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.

Evaluation of high hydrostatic pressure effect on human adenovirus using molecular methods and cell culture

Human adenoviruses (HAdV) are shed in human faeces and can consequently contaminate environmental waters and possibly be transferred to foods by irrigation. Therefore, efficient inactivation technologies for water and foods are needed. High hydrostatic pressure (HHP) processing is a non-thermal, energy-efficient and rapid emergent inactivation technology, which has been widely studied to eliminate pathogenic microorganisms in foods. We have applied HHP to HAdV-2 in water and cell culture medium (CCM) and measured the effect on virus infectivity and genome and capsid integrity, by using infectivity assay, real-time PCR (qPCR) and qPCR with prior enzymatic treatment (ET-qPCR) with Proteinase K and DNase I. While lower pressures did not provide satisfactory inactivation levels, 400 and 600 MPa treatments were estimated to reduce virus infectivity by approximately 6 log₁₀ units when effectively applied for 93s and 4s, respectively (i.e., excluding come up times of the pressure unit). However, virus genome remained intact even when higher pressures were applied. While acidic pH protected HAdV-2 from inactivation with HHP, no baroprotective effect was observed when 1% sucrose was added to the CCM. On the other hand, 10 mM CaCl₂ added to the CCM was estimated to protect HAdV-2 from HHP with longer treatment times (>10 min). When virus was treated in bottled mineral water, significantly higher infectivity reduction was observed compared to the same treatment in CCM. In conclusion, HHP was shown to effectively reduce HAdV-2 infectivity up to 6.5 log₁₀ units within 4s and can thus contribute to public health protection for food- and water-borne virus transmission. However, its precise effect is matrix dependent and therefore matrix-specific evaluations need to be considered for assuring reliable inactivation in practice.

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.

Thermal stability of structurally different viruses with proven or potential relevance to food safety

Aims:  To collect comparative data on thermal stability of structurally different viruses with proven or potential relevance to food safety.

Methods and Results:  Suspensions with poliovirus Sabin1, adenovirus type5, parechovirus1, human norovirus (NoV) GII.4, murine NoV (MNV1) and human influenza A (H1N1) viruses were heated at 56 and 73°C. Infectivity was tested by culture assay for all but human NoV GII.4 that cannot be cultivated in vitro. Time to first log₁₀ reduction (TFL‐value) was calculated based on best fit using the monophasic, biphasic or Weibull models. The Weibull model provided the best fit at 56°C for all viruses except influenza virus. The TFL at 56°C varied between a high of 27 min (parechovirus) to a low of 10 s (adenovirus) and ranked parechovirus > influenza > MNV1 > poliovirus > adenovirus. The monophasic model best described the behaviour of the viruses at 73°C, in which case the TFL was MNV1(62s) > influenza > adenovirus > parechovirus > poliovirus(14s).

Conclusions:  Viruses do not follow log‐linear thermal inactivation kinetics and the thermostability of parechovirus and influenza virus is similar to that of proven foodborne viruses.

Significance and Impact of the Study:  Resistant fractions of viruses may remain infectious in thermal inactivation processes and inactivation of newly discovered or enveloped viruses in thermal food preparation processes should not be assumed without further testing.

QMRAspot: a tool for Quantitative Microbial Risk Assessment from surface water to potable water

In the Netherlands, a health based target for microbially safe drinking water is set at less than one infection per 10,000 persons per year. For the assessment of the microbial safety of drinking water, Dutch drinking water suppliers must conduct a Quantitative Microbial Risk Assessment (QMRA) at least every three years for the so-called index pathogens enterovirus, Campylobacter, Cryptosporidium and Giardia. In order to collect raw data in the proper format and to automate the process of QMRA, an interactive user-friendly computational tool, QMRAspot, was developed to analyze and conduct QMRA for drinking water produced from surface water. This paper gives a description of the raw data requirements for QMRA as well as a functional description of the tool. No extensive prior knowledge about QMRA modeling is required by the user, because QMRAspot provides guidance to the user on the quantity, type and format of raw data and performs a complete analysis of the raw data to yield a risk outcome for drinking water consumption that can be compared with other production locations, a legislative standard or an acceptable health based target. The uniform approach promotes proper collection and usage of raw data and, warrants quality of the risk assessment as well as enhances efficiency, i.e., less time is required. QMRAspot may facilitate QMRA for drinking water suppliers worldwide. The tool aids policy makers and other involved parties in formulating mitigation strategies, and prioritization and evaluation of effective preventive measures as integral part of water safety plans.

Estimation of the likelihood of fecal-oral HEV transmission among pigs

Sources for human hepatitis E virus (HEV) infections of genotype 3 are largely unknown. Pigs are potential animal reservoirs for HEV. Intervention at pig farms may be desired when pigs are confirmed as a source for human infections, requiring knowledge about transmission routes. These routes are currently understudied. The current study aims to quantify the likelihood of pig feces in causing new HEV infections in pigs due to oral ingestion. We estimated the daily infection risk for pigs by modeling the fate of HEV in the fecal-oral (F-O) pathway. Using parameter values deemed most plausible by the authors based on current knowledge the daily risk of infection was 0.85 (95% interval: 0.03-1). The associated expected number of new infections per day was ∼4 (2.5% limit 0.1, the 97% limit tending to infinity) compared to 0.7 observed in a transmission experiment with pigs, and the likelihood of feces causing the transmission approached 1. In alternative scenarios, F-O transmission of HEV was also very likely to cause new infections. By reducing the total value of all explanatory variables by 2 orders of magnitude, the expected numbers of newly infected pigs approached the observed number. The likelihood of F-O transmission decreased by decreasing parameter values, allowing for at most 94% of infections being caused by additional transmission routes. Nevertheless, in all scenarios F-O transmission was estimated to contribute to HEV transmission. Thus, despite the difficulty in infecting pigs with HEV via oral inoculation, the F-O route is likely to cause HEV transmission among pigs.

The course of hepatitis E virus infection in pigs after contact-infection and intravenous inoculation

Background

Worldwide, hepatitis E virus (HEV) genotype 3 is observed in pigs and transmission to humans is implied. To be able to estimate public health risks from e.g. contact with pigs or consumption of pork products, the transmission routes and dynamics of infection should be identified. Hence, the course of HEV-infection in naturally infected pigs should be studied.

Results

To resemble natural transmission, 24 HEV-susceptible pigs were infected either by one-to-one exposure to intravenously inoculated pigs (C1-pigs; n = 10), by one-to-one exposure to contact-infected pigs (C2-pigs: n = 7; C3-pigs: n = 5) or due to an unknown non-intravenous infection route (one C2-pig and one C3-pig). The course of HEV-infection for contact-infected pigs was characterized by: faecal HEV RNA excretion that started at day 7 (95% confidence interval: 5–10) postexposure and lasted 23 (19–28) days; viremia that started after 13 (8–17) days of faecal HEV RNA excretion and lasted 11 (8–13) days; antibody development that was detected after 13 (10–16) days of faecal HEV RNA excretion. The time until onset of faecal HEV RNA excretion and onset of viremia was significantly shorter for iv-pigs compared to contact-infected pigs, whereas the duration of faecal HEV RNA excretion was significantly longer. At 28 days postinfection HEV RNA was detected less frequently in organs of contact-infected pigs compared to iv-pigs. For contact-infected pigs, HEV RNA was detected in 20 of 39 muscle samples that were proxies for pork at retail and in 4 of 7 urine samples.

Conclusion

The course of infection differed between infection routes, suggesting that contact-infection could be a better model for natural transmission than iv inoculation. Urine and meat were identified as possible HEV-sources for pig-to-pig and pig-to-human HEV transmission.