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African Swine Fever Virus (ASFV) is the cause of an infectious disease in pigs, which is difficult to control. Long viability of ASFV has been shown for several contaminated materials, especially under low temperature. Therefore, when pigs are exposed to a contaminated environment, new infections could occur without the presence of infectious individuals. For example, a contaminated, poorly washed, empty livestock vehicle poses a risk to the next load of pigs. A quantitative stochastic environmental transmission model was applied to simulate the change in environmental contamination levels over time and calculate the epidemic parameters through exposure-based estimation. Due to the lack of experimental data on environmental transmission at low temperatures, we performed a non-linear fit of the decay rate parameter with temperature based on a literature review. Eventually, 16 scenarios were constructed for different temperature (at 20 °C, 10 °C, 0 °C, or -10 °C) and duration of empty periods (1, 3, 5, or 7 days) after the environment had been contaminated. We quantified the variation in the contamination level of the environment over time and the probability of newly added recipients getting infected when exposed to the environment after the empty period. As a result, the transmission rate parameter for ASFV in pigs was estimated to be 1.53 (0.90, 2.45) day -1 , the decay rate parameter to be 1.02 (0.73, 1.47) day -1 (at 21 °C), and the excretion rate parameter to be 2.70 (2.51, 3.02) day -1 . Without washing and disinfecting, the environment required 9, 14, 24, 54 days to reach a low probability of causing at least one new case (<0.005) at 20 °C, 10 °C, 0 °C, -10 °C, respectively. In addition, the method proposed in this paper enables assessment of the effect of washing and disinfecting on ASFV environmental transmission. We conducted this study to better understand how the viability of ASFV at different temperatures could affect the infectivity in environmental transmission and to improve risk assessment and disease control strategies., Competing Interests: Declaration of Competing Interest The following authors report specific relationships that could be interpreted as implying a conflict: Lis Alban and Lisbeth Harm Nielsen work for Danish Agriculture & Food Council, which gives advice to farmers and meat producing companies. The remaining authors declare no conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

In 2020, the Danish competent authority (CA) raised questions about the Salmonella exposure risk to consumers from bile-contaminated pig carcasses. This study assesses this risk related to sow carcasses. A total of 300 bile samples were collected aseptically at a large Danish sow abattoir. A selective method and medium, RAPID'Salmonella, was used to detect Salmonella and other family members. MALDI-TOF was used to identify bacterial species. None of the 300 bile samples were positive for Salmonella. A simulation model was set up to estimate the number of bile-contaminated carcasses with Salmonella that would go unnoticed on the market if the food business operator (FBO) had full responsibility for handling bile contamination. Data originated from our own and previous data collection, the Danish Meat Inspection Database and expert opinion from the CA and FBO. The FBO-scenario showed that a median of one (90% C.I. 0 - 7) carcasses carrying bile contamination with Salmonella would go unnoticed out of 281,000 in one year, whereas the CA-scenario showed a median of 14 (90% C.I. 1 - 63) such carcasses. Hence, the role of bile contamination on sow carcasses for the exposure of consumers to Salmonella seems to be negligible. Still, the FBO should be encouraged to prevent bile contamination., Competing Interests: Declaration of Competing Interest The authors declare no known competing interests financially or personally that could have influenced the work of this paper. LA, LL and VM work for an organization which provides advice for farmers and food-producing companies. MJ, BS and HI work for or are associated with the University of Copenhagen. LA is an Adjunct Professor at University of Copenhagen., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Toxoplasma gondii infection in pigs is commonly diagnosed using serological tests that detect IgG antibodies targeted against the parasite. Such tests include enzyme-linked immunosorbent assay (ELISA), modified agglutination test (MAT), and western blot (WB), which are commercially available as rapid test kits. In this study, we evaluated the manufacturer recommended cut-off of ELISA-PrioCHECK test kit and determined a new optimal cut-off for identifying T. gondii infections in pigs. Assessment of the commercial ELISA kit was done by including data from two additional serological tests, MAT, and WB, applied to seven pig population categories with varying prevalences. A total of 233 plasma samples that were previously used in other studies for investigating T. gondii seroprevalence in pigs in Denmark were randomly selected for inclusion, including 95 samples that had previously been analysed with all three tests and an additional 138 samples that were analysed using the three serological tests for this study. In the absence of a gold standard test, a latent class model was fit to the data to obtain estimates of sensitivity and specificity for each of the tests along with prevalence in each of the populations. A cut-off that maximized the sensitivity and specificity of the ELISA test was then selected. The optimal cut-off value for percent of positive control (PP) in ELISA-PrioCHECK was estimated to be 27.7 PP, which is higher than the cut-off value of 20 PP that is recommended by the manufacturer. At this cut-off, the estimated sensitivities of ELISA, MAT and WB were 99.2% (96.3-100.0%), 96.3% (88.0-100.0%), and 89.8% (80.0-98.0%), respectively. The estimated specificities of ELISA, MAT and WB were 95.2% (92.5-97.6%), 99.6% (97.5-100.0%), and 98.2% (95.9-100.0%), respectively. Our findings have broad relevance to the use of the ELISA-PrioCHECK test kit for detecting Toxoplasma gondii infection in pigs., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Pigs are one of several host species for Toxoplasma gondii parasites, and consumption of infected pork may lead to toxoplasmosis in humans. We estimated seroprevalence in sows and finishers from conventional and organic herds in Denmark and discussed the strategies for reducing the risk from pork. We collected 447 blood samples from 59 herds, and additional meat-juice samples from 212 of the same pigs. Using a T. gondii IgG commercial ELISA test, we found 2% (95% CI = 0.4%-5%) apparent seroprevalence of T. gondii in conventional finishers, 11% (95% CI = 6%-17%) in organic finishers, 19% (95% CI = 11%-30%) in conventional sows and 60% (95% CI = 47%-72%) in organic sows. The odds of an animal testing positive for T. gondii was 16 times higher (95% CI = 4.6-74.3) in organic compared to conventional herds. The odds were 22 times higher (95% CI = 6.5-88.3) if the animal was a sow compared to a finisher. Meat-juice ELISA values were significantly correlated with plasma results (P < 0.001), but on average 64% of the blood-plasma ELISA values. Lowering the recommended cut-off from 20 to 13 percent positive values of the positive control for meat-juice ELISA, resulted in the meat-juice ELISA identifying 93% of the plasma positives as positive and 99% of the plasma negatives as negative. The time taken to detect one or more infected pigs from a T. gondii positive herd at slaughter was estimated using abattoir data on pigs (17,195,996) and batches (165,569) delivered to Danish abattoirs in 2018. The time to detection was affected by the seroprevalence, frequency at which the pigs were delivered, the number of samples tested per batch delivery and the batch sizes. Time to detection was long in conventional finisher herds due to low prevalence, and in sow herds because of intermittent delivery of a low number of sows. In organic finisher herds, time to detection was short due to medium prevalence and frequent delivery of a high number of finishers. Conventional finisher herds may be classified as low-risk, organic finisher herds as medium-risk, and conventional and organic sow herds as high-risk herds. Risk-mitigation strategies at processing plants (freezing or curing) or at the consumer level (heat treatment) for meat originating from high-risk herds, surveillance of medium-risk herds, and auditing for controlled housing (high biosecurity) in low-risk herds may be cost-effective alternatives to serological surveillance of all Danish pig herds., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

The use of antimicrobials in livestock constitutes an increasing global concern, and many countries pursue approaches to reduce the amount used, particularly in the pig production industry. The EU Commission has decided, due to environmental concerns, to phase out use of zinc oxide in pigs by 2022. This poses an additional challenge to efforts to reduce antimicrobial use (AMU) in European pig production. The pig production sector needs further information about how to comply with official AMU requirements without losing competitiveness. The most efficient approaches are likely to involve a combination of multiple factors. Therefore, the objective of this study was to explore multidimensional associations between biosecurity, productivity, vaccination and AMU. A cross sectional study was conducted using data from 160 Danish sow herds in 2014-2015. Biosecurity data were collected through computer-assisted telephone interviews using a pre-developed questionnaire (Biocheck.UGent®) supplemented with additional country-specific questions and translated into Danish. Herd-specific data, consisting of antimicrobial prescriptions, purchase of vaccines against five endemic infections, herd health status and one productivity measure (i.e. number of weaned piglets per sow per year) were extracted from various databases. Factor analysis was conducted on a subset of the data from 152 herds with sufficiently complete data. The identified factors were explained by evaluating data from herds with extreme loadings on the respective factor. The results were further discussed based on plots combining herd factor loadings on two factors at a time. Four factors were selected based on the break-point in the scree-plot. Factor 1 included herd type, herd size, and age of farm buildings. Factor 2 covered general biosecurity, including several internal and external biosecurity measures. Factor 3 represented preventive measures implying specific focus on avoiding introduction of ASF by foreign employees. Lastly, Factor 4 covered vaccination status, specifically regarding vaccination against Mycoplasma hyopneumoniae and Porcine Reproductive and Respiratory Syndrome virus. These factors were used to group the 152 sow herds into herd typologies. Feasible strategies aimed at improving health by reducing AMU without hampering animal welfare were identified and discussed for each typology. AMU and productivity correlated only weakly with other variables. This is probably due to limited variability in both these variables in study herds, which might be attributed to official restrictions on AMU, and a general high level of health and biosecurity in Danish sow herds., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In modern livestock farming, there is an increasing understanding that antimicrobial (AM) consumption must be kept low - preferably without compromising animal welfare or productivity. This requires an understanding of the relationship between AM use, productivity, biosecurity, vaccination and herd demographics. To obtain this, we undertook an Additive Bayesian Network analysis using data from 2014 to 2015, covering 157 Danish sow herds with weaners. In general, productivity and biosecurity were high, and AM consumption low. No association was found between prescribed AM and productivity. Other variables, such as biosecurity and enrolment in the Danish Specific Pathogen Free (SPF) system, had stronger associations with sow productivity than AM consumption. In the weaner unit, an association between AM consumption and certain vaccination practices was found, suggesting that vaccines might be used to control preexisting problems. The results reveal that most Danish sow producers are able to maintain productivity while using low amounts of AMs. This conclusion must be interpreted within the context of Danish pig farming i.e. generally high biosecurity and many years of official restrictions aiming at reducing AM consumption., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Reduction of antimicrobial use (AMU) in pigs is a priority to counteract development of antimicrobial resistance in animal and human pathogens. However, there is concern that Danish pig producers complying with official AMU restrictions might experience reduced herd health and productivity in the future, if alternative strategies are not available. Vaccination has been suggested as a strategy to prevent disease and minimise the need for antimicrobial treatments. The aim of this register-based study was to assess the associations between data on vaccination, productivity and AMU in Danish finisher herds over a 4-year period following initiation of the Yellow Card, which is a restrictive AMU control scheme. For each of the years 2011 to 2014, sow herds were grouped according to purchase patterns regarding Porcine Circovirus Type 2 (PCV2) (use/no use). For the sow herds (N = 179-433), additional information of purchases of vaccines against Mycoplasma hyopneumoniae (MYC), Actinobacillus pleuropneumoniae (APP), Porcine Reproductive and Respiratory Syndrome virus (PRRS) and Lawsonia intracellularis (LAW) was included. By use of movement data, finisher herds receiving pigs from the sow herds were tracked and included in the analyses. Finisher herds (N = 40-62) with register data on productivity (i.e. average daily weight gain, feed conversion rate, mortality and lean meat percentage) and data on prescriptions of antimicrobials measured in Animal Daily Doses/100 finishers/day as well as the proportion of parenteral AMU treatments out of all treatments (AMU-ratio) were included. Univariable combinations were tested for statistically significant associations (P < 0.05) and included in multivariable linear mixed-effects model for each of the six outcome variables representing productivity (N=4) or AMU (N=2). Herd number was included as a random effect to account for the herds appearing more than once. The variables representing PCV2, enrolment in the Danish Specific Pathogen Free (SPF) system, year, herd type and herd size were included as potential confounders. Vaccination against PRRS and higher AMU for finishers were associated with increased lean meat percentage, potentially due to disease outbreaks resulting in reduced growth of the pigs and lower carcass weight at slaughter in herds with PRRS. None of the other types of vaccines was associated with any of the productivity outcomes. Vaccination against PCV2, PRRS and APP were associated with higher levels of AMU, and vaccination against LAW with a higher AMU-ratio. This may be explained as some farmers preferring to take action soon after observing disease problems. No association was found between vaccination against MYC and AMU. Herds enrolled in SPF had significantly higher average daily weight gain than non-SPF herds., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The present paper provides an overview of the costs of preventive activities, currently undertaken in Denmark, related to foot and mouth disease (FMD) and classical and African swine fever (SF). Only costs held between outbreaks were included. Costs were divided into public costs and costs paid by the pig and cattle industries, respectively. Data were retrieved from multiple sources such as databases, legal documents, official statistics, yearly reports and expert opinions. As no previous studies have assessed such costs, data collection and estimation procedures were discussed and decided upon in a group of experts from universities, industry, and public authorities. The costs of each preventive activity were related to the type of activity, the number of times the activity was carried out and the share of costs that could be associated with FMD or SF. Uncertainty about parameters was incorporated in the analysis by assuming that the FMD/SF shares of costs as well as total costs for each activity could take on a most likely as well as a minimum and maximum value. A high degree of transparency was prioritized in the cost analysis, which enables reproducibility and easy access to conducting sensitivity analyses. A total of 27 FMD/SF preventive activities were identified. The estimated median (minimum-maximum) of total costs amounted to €32 (18-50) million in 2013. The single most costly FMD/SF related activity, amounting to €8 (5-13) million or 26% of total costs, was a national legal requirement to clean lorries immediately after transportation of live animals. The distribution of costs between stakeholders was estimated to be as follows: pig industry 63%, cattle industry 27%, and the public authorities 10%. Most of the activities focused on reducing the probability of spreading FMD/SF, while only a few activities were directed mainly towards reducing the probability of introduction. Legally required FMD/SF activities (mainly based on EU legislation) accounted for 60% of the activities, while FMD/SF related measures agreed on at sector level and measures implemented due to individual initiatives, such as farmer's investment in specially built delivery facilities, each accounted for 20%., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In Denmark, a monitoring program for residues of antimicrobials in pork is in place involving annual testing of around 20,000 samples from finishing pigs corresponding to 0.1% of the animals slaughtered. Annually, zero to two samples are found above the maximum residue limit. Both authorities and industry have expressed interest in adjusting the monitoring to a risk-based system. The objective of this study was to assess the opportunities and consequences of the monitoring considering: 1) replacing the current bioassay with high-performance liquid chromatography-mass spectrometry (HPLC LC-MS/MS), 2) replacing kidney with muscles as sample matrix, and 3) using indicators to identify high-risk (HR) herds and increase sampling intensity in these herds, lowering sampling in the low-risk (LR) herds, while aiming at continued detection of similar numbers of test-positives at the lowest possible costs. A state-of-the-art stochastic scenario tree modelling approach including economic evaluation of different model outcomes was used. A total of six scenarios were run for penicillin and tetracycline, respectively. Relevant information was obtained through the literature, statistical analysis of existing data as well as consultations with laboratory and slaughterhouse experts. Abattoir recordings of chronic pleuritis were used as an indicator for finishing pig herds (HR=within-herd prevalence>40%). Such risk-based monitoring would have to use muscles and not kidneys, because of logistic challenges in identifying and storing of plucks until testing. However, the bioassay cannot be used on muscle tissue due to low sensitivity for tetracyclines. Different plausible combinations of sample sizes were also modelled. The HPLC LC-MS/MS method detected the same number of cases compared to the bioassay when kidney was used as matrix. HPLC LC-MS/MS has a higher sensitivity when used on muscle but it is almost twice as costly as the bioassay. Risk-based sampling resulted in detection of more residue cases with higher cost-effectiveness than random monitoring. Sampling 7500 HR pigs and 5000 LR pigs resulted in the most cost-effective monitoring among the alternative scenarios. The associated costs would increase by 4%. A scenario involving testing of 5000 HR and 5000 LR animals would result in slightly fewer positives, but 17% savings in costs. The advantages of using HPLC LC-MS/MS compared to the bioassay are a fast response and a high sensitivity for all relevant substances used in pigs. The Danish abattoir companies have implemented a risk-based monitoring similar to the above per January 2016., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Denmark was considered not to have an established population of free-ranging wild boar. Today, sporadic observations of wild boar challenge that view. Due to its reservoir role for economic devastating swine diseases, wild boar represents a potential threat for Denmark's position as a large pig- and pork-exporting country. This study assessed the prospects of wild boar invasion in Denmark. Multi-source citizen science data of wild boar observations were integrated into a multi-modelling approach linking habitat suitability models with agent-based, spatially-explicit simulations. We tested whether the currently observed presence of wild boar is due to natural immigration across the Danish-German border, or whether it is more likely that wild boar escaped fenced premises. Five observational data sources served as evaluation data: (1) questionnaires sent to all 1625 registered owners of Danish farm land, located in the 60 parishes closest to the border, (2) an online questionnaire, (3) a mobile web-based GPS application, (4) reports in the media or by governmental agencies, and (5) geo-referenced locations of fenced wild boar populations. Data covering 2008-2013 included 195 observations of wild boar, including 16 observations of breeding sows. The data from the Danish Nature Agency and the mailed questionnaires were consistent regarding the location of wild boar observations, while data from the Danish Veterinary and Food Administration, the media and the electronic questionnaires documented individual scattered observations in the rest of Jutland. Most observations were made in the region bordering Germany. It is uncertain whether the relatively few observations represent an established population. Model outcomes suggested that the origin of wild boar in about half of the area with sporadic observations of wild boar could be attributed to spatial expansions from a local Danish population near the border and consisting of wild boar originally of German origin. However, the other half, located distant to the border, were likely a result of animals escaping fenced premises inside the country. The approach serves as a template to assess the status of an invading species and improve the knowledge base for risk assessment and management decision., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Denmark has been recognized as officially free (OTF) from bovine tuberculosis (bTB) since 1980. In this study, we estimated the annual probability (PIntro) of introducing Mycobacterium bovis into the Danish cattle population, through (a) imports of cattle and (b) foreign personnel working in Danish cattle herds. Data from 2000 to 2013 with date, number and origin of imported live cattle were obtained from the Danish Cattle Federation. Information on immigrants working in Danish cattle herds was obtained through a questionnaire sent by email to a sample of Danish cattle farmers (N=460). Inputs obtained from data analysis, expert opinion, the questionnaire and literature were fed into three stochastic scenario tree models used to simulate the effect of import trade patterns, and contact between immigrant workers and cattle. We also investigated the opportunity of testing animals imported from OTF countries by tuberculin skin test and animals from non-OTF countries by interferon-γ test (IFN-γ), exemplified by using year 2009 where the number of imported animals was higher than usual. Results showed that PIntro is driven mainly by importation of live cattle. The combined median annual probability of introducing M. bovis into the Danish cattle population by either imported live cattle or infectious immigrant workers, ranged from 0.3% (90% prediction interval (P.I.): 0.04%:1.4%) in 2001 to 4.9% (90% P.I.: 0.6%; 19.2%) in 2009. The median of the median PIntro estimates from the 14 years was 0.7% (median of 90% P.I.: 0.08%; 3.5%). Hence, on average, at least one introduction each 143 years could be expected, if the annual number of imported animals does not change remarkably in the future. If the number of imported animals increases, compared to the years we analyzed, additional testing of imported cattle might be considered. For example, in 2009, PIntro would have been reduced from 4.9% to 0.8% (90% P.I.: 0.1%; 4.7%) if animals from OTF countries had been tested with the tuberculin skin test and animals from non-OTF countries had been tested with the IFN-γ test. The presented model could be used easily in other countries with similar bTB status to Denmark, where wildlife represents a negligible probability of infection for domestic cattle and where the imported live cattle represent the main pathway of bTB introduction into the local cattle population., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Tuberculosis is a zoonosis caused by Mycobacterium spp. International trade in cattle is regulated with respect to Mycobacterium bovis (M. bovis) but not Mycobacterium tuberculosis (M. tuberculosis), despite that cattle can become infected with both species. In this study we estimated the annual probability (PIntro) of introducing M. tuberculosis into the Danish cattle population, by the import of cattle and/or by immigrants working in Danish cattle herds. Data from 2013 with date, number, and origin of imported live cattle were obtained from the Danish cattle database. Information on immigrants working in Danish cattle herds was obtained through a questionnaire sent to Danish cattle farmers. The gained inputs were fed into three stochastic scenario trees to assess the PIntro for the current and alternative test-and-manage strategies, such as testing of imported animals and/or testing immigrant workers with the tuberculin skin test. We considered the population of Danish farmers and practitioners free of tuberculosis, because in Denmark, the incidence of the disease in humans is low and primarily related to immigrants and socially disadvantaged people. The median annual probability of introducing M. tuberculosis into the Danish cattle population due to imported live cattle was 0.008% (90% P.I.: 0.0007%; 0.03%), while the probability due to immigrant workers was 4.1% (90% P.I.: 0.8%; 12.1%). The median combined probability (PIntro) due to imported cattle plus workers was 4.1% (90% P.I.: 0.8%; 12.6%). Hence, on average at least one introduction each 24 (90% P.I.: 8; 125) years could be expected. Imported live cattle appeared to play a marginal role on the overall annual PIntro, because they represented only approximately 0.2% of the median annual probability. By testing immigrant workers the overall annual PIntro could be reduced to 0.2% (90% P.I.: 0.04%; 0.7%). Thus, testing of immigrant workers could be considered as a risk mitigation strategy to markedly reduce the likelihood of introducing M. tuberculosis into the Danish cattle population, if the risk is considered unacceptable by the veterinary public health authorities., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We compared two published studies based on different output-based surveillance models, which were used for evaluating the performance of two meat inspection systems in cattle and to substantiate freedom from bovine tuberculosis (bTB) in Denmark. The systems were the current meat inspection methods (CMI) vs. the visual-only inspection (VOI). In one study, the surveillance system sensitivity (SSe) was estimated to substantiate the bTB free status. The other study used SSe in the estimation of the probability of freedom (PFree), based on the epidemiological concept of negative predictive value to substantiate the bTB free status. Both studies found that changing from CMI to VOI would markedly decrease the SSe. However, the two studies reported diverging conclusions regarding the effect on the substantiation of Denmark as a bTB free country, if VOI were to be introduced. The objectives of this work were: (a) to investigate the reasons why conclusions based on the two models differed, and (b) to create a hybrid model based on elements from both studies to evaluate the impact of a change from CMI to VOI. The hybrid model was based on the PFree approach to substantiate freedom from bTB and was parametrized with inputs according to the newest available information. The PFree was updated on an annual basis for each of 42 years of test-negative surveillance data (1995-2037), while assuming a low (<1%) annual probability of introduction of bTB into Danish cattle herds. The most important reasons for the difference between the study conclusions were: the approach chosen to substantiate the bTB free status (SSe vs. PFree) and the number of years of surveillance data considered. With the hybrid model, the PFree reached a level >95% after the first year of surveillance and remained ≥96% with both the CMI and VOI systems until the end of the analyzed period. It is appropriate to use the PFree of the surveillance system to substantiate confidence in bTB free status, when test-negative surveillance results can be documented over an extended period of time, while maintaining a low probability of introduction of bTB into the cattle population. For Denmark, the probability of introduction of bTB should be kept <1% on an annual basis to sustain the high confidence in freedom over time. The results could be considered when deciding if the CMI can be replaced by VOI in cattle abattoirs of countries for which bTB freedom can be demonstrated., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Around 20,000 samples are analysed each year for the presence of antibacterial residues in Danish finisher pigs, and between zero and five samples are detected positive above the maximum residue level (MRL). The intention was to develop a risk-based surveillance programme involving fewer samples while ensuring equal sensitivity. Therefore, risk indicators were searched for. Data were obtained from the Danish slaughterhouse database covering the period from July 2010 to December 2012. Residues were found or suspected in 17 incidents. In nine of these, the farmer had called in to prevent the pigs from being slaughtered. Hence, eight suspect cases were found through the surveillance programme, and two of these were above MRL. For these eight case herds, the number of pigs slaughtered and the number in which each of the following lesions were found were included in a statistical analysis: chronic pleuritis, tail bite, chronic pericarditis, chronic pneumonia, chronic peritonitis, osteomyelitis, abscess in hindquarters, abscess in leg/toe and abscess in forequarters. Only chronic pleuritis was associated with the presence of residues. Next, data from all herds delivering pigs for slaughter to the same abattoir were included covering a 3-month period prior to the residue finding. The prevalence of chronic pleuritis was on average 1.7 times higher in the eight case herds compared to all other herds. In two herds, the prevalence was significantly higher (P≤0.05), and in one herd substantially higher, but only borderline significant (P=0.1). In the remaining herds, the prevalence did not differ from the other herds delivering pigs to the abattoir. This indicates that chronic pleuritis might be considered as a risk indicator for use in surveillance. Other risk indicators/factors - reported in the cases where the farmers called in - were inadequate marking of treated animals and incorrect use of medication dispensers. These factors are not suited for use in surveillance and should be dealt with otherwise., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The information provided by animal-health surveillance helps to reduce the impact of animal diseases. The widespread movement of animals and their products around the world results in an increasing risk that disease will spread. There is, therefore, a need for exchange between countries of comparable information about disease incidence; the exchange must be based on a common understanding of surveillance approaches and how surveillance systems are designed and implemented. Establishing agreed-upon definitions of surveillance terms would be a first step in achieving this standardisation, and will enhance transparency and confidence. To this end, a workshop was held with the aim of agreeing upon key terms and concepts for animal-health surveillance. In this paper, we describe the methods used at the workshop and summarise the discussions. A complete list of all the proposed definitions including lists of characteristics that can be used to describe surveillance activities and attributes for evaluation of surveillance is available in the workshop report (available at http://www.defra.gov.uk/ahvla-en/disease-control/surveillance/icahs-workshop/). Some important issues were highlighted during these discussions; of particular note was the importance of economic efficiency as an evaluation attribute. Some remaining inconsistencies in the proposed use of terms are highlighted (including the definition of 'risk-based surveillance' and the use of the term 'event-based surveillance')., (Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.)

Current EU regulation requires that every bovine carcass is examined for bovine cysticercosis (BC) at meat inspection. This is costly and might be superfluous at low BC prevalence. However, from a consumer view-point it may be important to identify and manage infected carcasses to avoid human infection. If relevant data could be effectively used to classify animals with respect to their risk of being infected, then the current meat inspection could be replaced by a more cost-effective system targeting high-risk animals. This study aimed to (1) describe the distribution of BC cases in the Danish cattle population, (2) estimate the animal level prevalence (3) provide descriptive statistics of potential risk factors for BC, and (4) determine attributable risks and fractions of selected risk factors potentially useful for a future risk-based meat inspection system. In total, 348 cases of BC were recorded among all cattle slaughtered (n=4,090,661) in Denmark between 2004 and 2011. The true animal level prevalence of BC was estimated to be 0.06%. The herd of origin of the cases were defined as the herd in which the animals spent most of their lifetimes. The detected cases were found to originate from 328 herds, with a maximum of two cases per herd indicating sporadic occurrence. Even though organic farming was associated with a higher risk (RR=1.9 in univariable analysis) of BC-positive animals being detected at slaughter, the population attributable fraction showed that only 5% of the animals with BC could be attributed to organic farming practices at the level of organic farming practiced in Denmark in the study period. Thus, organic farming status was not a suitable risk factor to use to target future risk-based meat inspection. However, 54% of the animals with BC in the cattle population were attributed to female gender. Increasing age at slaughter was also associated with high risk of BC. There may be overlaps between these effects in animals with multiple risk factors. Other underlying factors such as grazing patterns might explain the risk factors and attribution results found in this study. However, grazing practices are currently not recorded in the Danish cattle database. Therefore, animal level risk factors such as age and gender together with other risk factors such as grazing practices might be included as food chain information, required to be provided by the farmer prior to slaughter. The challenges and opportunities of this approach should be investigated further., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Confirming freedom from disease is important for export of animals and animal products. In Denmark, an intensive surveillance program is in place for Aujeszky's disease (AD) and classical swine fever (CSF), including 34,974 blood samples tested for AD and 37,414 samples tested for CSF (2008 figures). In the current system, 3.5% of sows and boars for export or slaughter are tested for both diseases, as well as all boars before entering boar stations. Furthermore, nucleus herds are tested every third month for classical swine fever. We investigated, whether the sample size could be reduced without compromising the posterior probability of freedom (PostPFree) from AD and CSF by use of a scenario tree model. Conventional herds and sows or boars were defined as risk factors (compared to SPF(1) herds and finisher pigs), with a relative risk of 2 and 5, respectively. The probability of introduction was modeled as a distribution (0.0042:0.0083; 0.05), and the within-herd and between-herd design prevalence were set to 0.05 and 0.01, respectively. If 50 and 75% of the test results from exported or slaughtered sows and boars were simulated to be removed at random, while the blood samples from boar stations were kept constant (reflecting a total reduction of 28 or 43%) the PostPFree from AD was reduced from 0.989 after 1 year testing to 0.980 or 0.971, respectively. Similarly, the confidence of freedom from CSF was reduced from 0.989 to 0.982 or 0.969, when the number of serological samples from abattoirs and export sows and boars is reduced by 50 or 75%, respectively (reflecting a total reduction of 34 or 51%), and further to 0.978 or 0.963 if sampling in nucleus herds was stopped (reflecting a total reduction of 41 or 59%). The results show that a reduction in the sampling size of Danish sows will have limited effect on the PostPFree from AD and CSF, and that sampling in nucleus herds for CSF adds little to the PostPFree from CSF., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In 2010, the "yellow card scheme" which was adopted by the Danish Veterinary and Food Administration imposed restrictions on pig farmers who used more antimicrobials than twice the average. To study the potential impact on pig health, we looked into antimicrobial consumption and vaccine use data from the monitoring programme Vetstat, covering all treatments conducted on Danish pigs between January 2010 and July 2011. The decrease in antimicrobial consumption was pronounced for all age groups (sows/piglets, weaners and finishers) treated for either gastro-intestinal or respiratory disease. Evaluated over 12 months, use of vaccines increased in general: PCV2-related infections (+31%), gastro-intestinal disease (27%), respiratory infections (21%) whereas use of vaccines against other infections remained almost constant (-18%). Data from meat inspection of finisher pigs from before and after introduction of the scheme were compared. This included 1.7 million finisher pigs originating from 2765 pig farms, slaughtered on one large Danish abattoir and covered the first 9 weeks in 2010 and 2011, respectively. Nine lesions of chronic nature and infectious origin and the code "condemned" were selected. The prevalence of these lesions was calculated. Logistic regression models with year and week as explanatory variables were used to identify whether the prevalence of a lesion changed from 2010 to 2011. Possible clustering due to correlation within herds and between weekly shipments of animals originating from the same herd was taken into account in the models. The most common lesion seen was chronic pleuritis (∼23%) while the other lesions occurred less-commonly (<1%). For osteomyelitis, pleuritis, chronic arthritis and condemnation, no differences were observed between the 2 years. The prevalence of chronic peritonitis (OR=1.5), umbilical hernia (OR=1.2) and chronic enteritis (OR=1.2) were statistically higher in 2011 compared to 2010, whereas it was lower for tail bite infection (OR=0.6), chronic pericarditis (OR=0.6), and chronic pneumonia (OR=0.7) (P<0.001). Moreover, in the condemned carcasses, chronic pneumonia plummeted as a lesion found in 2011 compared to 2010 (OR=0.07, P<0.0001). Our results indicate that marked reduction in use of antimicrobials is associated with a short-term increase in the prevalence of specific lesions found during meat inspection and higher coverage of vaccines against respiratory diseases might impact the prevalence of chronic pneumonia positively. Other factors that impact on pig health were not included in the study. Moreover, effect of productivity was not evaluated., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Under the current EU meat inspection regulation, every single carcase from all bovines above 6 weeks of age has to be examined for bovine cysticercosis (BC). This is time-consuming, costly, and is of limited value in countries with low prevalence. The aim of this study was to develop a stochastic simulation model for analysis of tentative risk-based meat inspection systems for BC in Danish cattle with regard to system sensitivity (SSSe), specificity and potential monetary benefits compared to the current system, which has an estimated SSSe of 15%. The relevant risk factors used to construct three alternative scenario trees were identified from previous Danish risk factor studies (1) gender, (2) grazing and (3) access to risky water sources. Thus, females, animals that had been grazing or animals with access to risky water sources were considered high-risk and would be subjected to invasive inspection at meat inspection. All animals in the low-risk groups (i.e. males, non-grazing or no access to risky water sources, respectively) would be subjected to visual inspection only. It was assumed that half of the cattle were slaughtered in abattoirs that would be able to reorganise the work at the slaughterline, allowing them to do with one meat inspector less. All abattoirs would gain on the price of sold uncut beef from the masseter muscles from visually inspected cattle. Under these assumptions, using gender and grazing were preferable due to them having SSSe only slightly lower than the current system, and highest effectiveness ratios, but they had a lower net economic effect (NEE) than the scenario using risky water sources. Using gender to differentiate high and low-risk groups was judged preferable over grazing due to feasibility, because the information is readily available at the slaughter line. The exact total NEE for the cattle sector depends on how many and which of the abattoirs that would be able to reorganise the work at the slaughter line to save money on inspection of the head of carcases. Overall, the SSSe was low in all scenarios leading to undetected BC-positive cattle both in the current meat inspection and under the investigated risk-based meat inspection systems. Therefore, improving the sensitivity of the methods used for inspection of high-risk cattle would be beneficial., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Residues of pharmacological active substances or their metabolites might be found in food products from food-producing animals. Maximum Residue Limits for pharmacological active substances in foodstuffs of animal origin are established to assure high food safety standards. Each year, more than 20,000 samples are analysed for the presence of antibacterial residues in Danish pigs. This corresponds to 0.1% of the size of the slaughter pig population and more than 1% of the sows slaughtered. In this study, a Bayesian model was used to evaluate the Danish surveillance system accuracy and to investigate the impact of a potential risk-based sampling approach to the residue surveillance programme in Danish slaughter pigs. Danish surveillance data from 2005 to 2009 and limited knowledge about true prevalence and test sensitivity and specificity were included in the model. According to the model, the true antibacterial residue prevalence in Danish pigs is very low in both sows (∼0.20%) and slaughter pigs (∼0.01%). Despite data constraints, the results suggest that the current screening test used in Denmark presents high sensitivity (85-99%) and very high specificity (>99%) for the most relevant antibacterial classes used in Danish pigs. If high-risk slaughter pigs could be identified by taking into account antibacterial use or meat inspection risk factors, a potential risk-based sampling approach to antibacterial residue surveillance in slaughter pigs would allow reducing the sample size substantially, while increasing or maintaining the probability of detection. Hence, the antibacterial residue surveillance programme in Danish pigs would be more cost-effective than today., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Each year, more than 167 million pigs in the European Union (EU) are tested for Trichinella spp. under the current meat hygiene regulations. This imposes large economic costs on countries, yet the vast majority of these pigs test negative and the public health risk in many countries is therefore considered very low. This work reviewed the current Trichinella status across the EU as well as the national level of monitoring and reporting. It also reviewed which animal species were affected by Trichinella and in which species it should be surveyed. This information was used to design a cost-effective surveillance programme that enables a standardised monitoring approach within the EU. The proposed surveillance programme relies on identifying sub-populations of animals with a distinct risk. Low-risk pigs are finisher pigs that originate from so-called controlled housing. All other pigs are considered high-risk pigs. Controlled housing is identified by the application of a specific list of management and husbandry practices. We suggest that member states (MS) be categorised into three classes based on the confidence that Trichinella can be considered absent, in the specified sub-population of pigs above a specified design prevalence which we set to 1 per million pigs. A simple and transparent method is proposed to estimate this confidence, based on the sensitivity of the surveillance system, taking into account the sensitivity of testing and the design prevalence. The probability of detecting a positive case, if present, must be high (>95 or >99%) to ensure that there is a low or negligible risk of transmission to humans through the food chain. In MS where the probability of a positive pig is demonstrated to be negligible, testing of fattening pigs from a sub-population consisting of pigs from controlled housing can be considered unnecessary. Furthermore, reduced testing of finishers from the sub-population consisting of pigs from non-controlled housing might even be considered, if conducted in conjunction with a proportionate sampling scheme and a risk-based wildlife surveillance programme where applicable. The proposed surveillance programme specifies the required number of samples to be taken and found negative, in a MS. A MS with no data or positive findings will initially be allocated to class 1, in which all pigs should be tested. When a MS is able to demonstrate a 95% or 99% confidence that Trichinella is absent, the MS will be allocated to class 2 or 3, in which the testing requirement is lower than in class 1., (Copyright © 2011 Elsevier B.V. All rights reserved.)

According to the current literature BVDV-infected neighbours probably impose a high risk of infection of susceptible cattle herds. In the present study, the objective was to evaluate the risk of a dairy herd changing infection status (from not having persistently infected (PI) animals to having PI-animals) in relation to location and infection status of neighbouring cattle herds in Denmark. In total, 7921 dairy herds were included in the analysis of spatial and non-spatial risk factors. The spatial risk factors were derived based on the cattle herds in the neighbourhood (N=36,639 cattle herds). The neighbourhood was defined as the first order neighbouring cattle herds using a Delauney triangularization. In total, 13.3% of the dairy herds changed herd status to PI-herds during the study period that lasted from January 1, 1995, to June 30, 1996. The risk of becoming a PI-herd was negatively associated with the mean distance to the neighbouring herds (OR=0.7 for an increase of 1 km). Presence of PI-herds in the neighbourhood increased the risk of becoming a PI-herd (OR=1.37, 1.40, 1.70 for 1, 2, ≥3 PI-herds in the neighbourhood). Increasing herd size increased the risk of becoming a PI-herd (OR=3.9 for an increase of 10 cows). Regional differences were seen., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In 1995, Denmark implemented a National Surveillance-and-Control Programme for Salmonella in finisher pigs. It was based on serological surveillance that enabled assignment of pig herds into three prevalence levels. Herds in levels 2 and 3 (corresponding to moderate and high Salmonella seroprevalence) were subjected to control measures, compulsory pen faecal sampling for bacteriological examination and serotyping. The initial dataset contained all herds that had mandatory bacteriological samples taken (N=3691 samples), out of which 44.4% were negative. Data from January 2005 to November 2007 obtained from the Danish programme were used to investigate the persistence of high serology (Salmonella index > or =40, corresponding to levels 2 or 3) for herds infected with one of the four most common Salmonella serotypes found in pig herds, S. Typhimurium, S. Derby, S. Infantis or S. Livingstone, using survival analysis. The effects of other potential factors, such as season, year, herd size and herd health status were also evaluated. An event was defined as return to low serology measured by a Salmonella index <40, for at least 6 consecutive months. A total of 1242 pig herds positive for one of the four serotypes of interest and 1433 events were included in the preliminary analysis using the Kaplan-Meyer method. The median high serology time (survival time) was 8 months and all explanatory variables were found to be significant (p<0.05), except the herd health status (p=0.49). Cox proportional hazards regression was used for herds infected with S. Typhimurium (N=1066) or S. Derby (N=314). Herds infected with S. Typhimurium presented a lower probability for returning to low serology (HR=0.69, p<0.001), compared to S. Derby, indicating longer high serology periods. Herds that started having high seroprevalence in Summer and Fall had a higher probability of returning to low serology compared to those starting in Winter and Spring (p<0.001). Compared to 2005, periods with high Salmonella serology were fewer and shorter in 2006 and 2007 (p<0.001). A positive impact of herd size was found, with larger herds being associated with shorter high serology periods, compared to smaller herds (p=0.012). This might indicate effective implementation of biosecurity measures in large herds. The health status of the herds was not found to be a significant factor (p=0.87), which might reflect that biosecurity measures in place in SPF herds are not effective for clearing Salmonella infections.

In 2006, total Danish pork exports were valued at 3.8 billion euros, corresponding to approximately 5% of the total Danish exports, and an outbreak of a notifiable disease would have dramatic consequences for the agricultural sector in Denmark. Several outbreaks of classical swine fever (CSF) have occurred in Europe within the last decade, and different control strategies have been suggested. The objective of this study was to simulate the epidemiological and economic consequences of such control strategies in a CSF epidemic under Danish conditions with respect to herd demographics and geography and to investigate the effect of extra biosecurity measures on farms. We used InterSpread Plus to model the effect of nine different control strategies: the minimum measures required by the EU plus depopulation of contact herds (EUplus), extra depopulation of neighbouring herds, extra surveillance within the protection and surveillance zones, extra biosecurity in SPF herds-or in all herds, vaccination of all pigs in the 1 or 2 km zones using live vaccine as a protective measure (vaccination-to-kill), vaccination of all weaners and finishers in the 1 or 2 km zones using an E2 marker vaccine as a suppressive measure (vaccination-to-live). Each epidemic was simulated to start in four different index herds: production herds located in low, medium and high pig density areas, respectively; and a nucleus herd in an area of high pig density. For each control strategy and index case, we calculated the size and duration of the epidemic, the number of depopulated and/or vaccinated herds and animals, the control costs borne by the public and the pig industry, respectively, as well as the loss of exports associated with the epidemic. The simulations showed that the EUplus strategy is the most effective of the evaluated strategies with respect to limiting the size, duration and cost of the epidemic, regardless of the index case. However, regarding the number of slaughtered animals, the vaccination-to-live strategies appeared to be more effective. Epidemics become larger and last longer if the index case is a nucleus herd. This implies that biosecurity in nucleus herds is extremely important to avoid transmission of CSF to these herds. Simulations showed that a Danish CSF epidemic will be moderate in most cases and will include fewer than 10 cases and last less than 2 weeks on average. However, for some iterations, long-lasting and large epidemics were observed. Irrespective of the size and duration, an epidemic is expected to be very costly due to the export losses.

Increasing demands for cost-effectiveness in surveillance for human health hazards from animal origins can be met by introducing risk-based principles. This e.g. implies targeting subpopulations with higher risk of infection compared to the whole population. Furthermore, historical data from surveillance can be collated and used to assess future risk of infection. To demonstrate the effectiveness of combining these two approaches, we used a model called "Discounting historical evidence". It depends mainly on the annual risk of introduction (PIntro) and the surveillance system sensitivity (SSe) (ability to detect infection if present). The model implies simulations that reiterate for a number of years. For each year the output is updated with the confidence on absence in infection. Trichinella spiralis infection in pigs is used as an example. In Denmark, more than 20 million pigs are tested annually. Despite more than 70 years of testing no pigs have been found positive for Trichinella. Hence, PIntro is low. SSe can be estimated from the maximum number of infected carcasses expected under the specified design prevalence, and the sensitivity of the test applied. According to our assessment, the current prevalence of Trichinella in Danish pigs is less than one case per million, which we interpret as negligible risk. Based on this, a risk-based surveillance programme for Trichinella is designed that targets all out-door reared pigs as well as all sows and boars (current total 610,000 slaughtered annually). These subpopulations are judged to have higher risk of getting Trichinella. Again, SSe and PIntro are estimated and the model results show that risk-based surveillance can be applied without jeopardizing human health. Finally, we incorporate wildlife surveys and test quality assurance in the programme. The results of the simulation model were included in an application to the European Commission concerning Denmark's status as a region with negligible risk of Trichinella. In July 2007, the European Commission granted status as "negligible risk" to Danish pigs and pork.

Denmark has no free-range wild-boar population. However, Danish wildlife organizations have suggested that wild boar should be reintroduced into the wild to broaden national biodiversity. Danish pig farmers fear that this would lead to a higher risk of introduction of classical swine fever virus (CSFV), which could have enormous consequences in terms of loss of pork exports. We conducted a risk assessment to address the additional risk of introducing and spreading CSFV due to the reintroduction of wild boar. In this paper, we present the part of the risk assessment that deals with the spread of CSFV between the hypothetical wild-boar population and the domestic population. Furthermore, the economic impact is assessed taking the perspective of the Danish national budget and the Danish pig industry. We used InterSpreadPlus to model the differential classical swine fever (CSF) risk due to wild boar. Nine scenarios were run to elucidate the effect of: (a) presence of wild boar (yes/no), (b) locations for the index case (domestic pig herd/wild-boar group), (c) type of control strategy for wild boar (hunting/vaccination) and (d) presence of free-range domestic pigs. The presence of free-range wild boar was simulated in two large forests using data from wildlife studies and Danish habitat data. For each scenario, we estimated (1) the control costs borne by the veterinary authorities, (2) the control-related costs to farmers and (3) the loss of exports associated with an epidemic. Our simulations predict that CSFV will be transmitted from the domestic pig population to wild boar if the infected domestic pig herd is located close to an area with wild boar (<5 km). If an outbreak begins in the wild-boar population, the epidemic will last longer and will occasionally lead to several epidemics because of periodic transfer of virus from groups of infected wild boar to domestic pig herds. The size and duration of the epidemic will be reduced if there are no free-range domestic pig herds in the area with CSF-infected wild boar. The economic calculations showed that the total national costs for Denmark (i.e. the direct costs to the national budget and the costs to the pig industry) related to an outbreak of CSF in Denmark will be highly driven by the reactions of the export markets and in particular of the non-EU markets. Unfortunately, there is a substantial amount of uncertainty surrounding this issue. If hunting is used as a control measure, the average expenses related to a CSF outbreak will be 40% higher if wild boar are present compared with not present. However, a vaccination strategy for wild boar will double the total costs compared with a hunting strategy.

Classical swine fever virus (CSFV) is a major infectious-disease agent of livestock and causes production losses through increased morbidity and mortality, particularly of young pigs. We identified the pathways for introduction of CSFV into Denmark and assessed the annual probability of introduction (based on a US Department of Agriculture model). We developed pathways based on material from scientific articles, reports from veterinary agencies and custom officers, and consultations with experts in the field. Returning livestock trucks and legal meat imports were the most important pathways for CSFV introduction to Denmark from other EU states with predicted overall likelihood of one or more introductions of CSFV within a median of 130 years (46-280) provided mitigating steps, such as cleaning trucks, were maintained to a very high standard. The likelihood would increase dramatically if these activities were abandoned: one or more introductions within a median of 5.2 years (2-14). The predicted risks from live-animal imports and semen were extremely low given the very few imports of these products. The most important countries for Denmark's CSFV risk are Germany and the Netherlands, though this risk is again predicted to be dramatically reduced as long as mitigating activities are maintained. We predicted the risk from illegal movements of pork into Denmark to be low because little pork enters through this route and only a small fraction of this pork would be fed to pigs.

In 2006, macrolides were withdrawn from the list of antibiotics recommended for veterinary treatment of diarrhoea in Danish pigs. The motive was to lower the antibiotic consumption in general and to mitigate the risk related to human infection with macrolide-resistant (Mres) Campylobacter. We subsequently conducted a risk assessment following international guidelines to address the risk for human health associated with usage of macrolides in Danish pigs. Data originated from surveillance programs, published papers, reports and statistics. Furthermore, an exposure model was built in @Risk. Mres Campylobacter is the hazard of interest. Data from different EU countries show that beef contains a very low prevalence (typically 0.1-1.1%) of Campylobacter; moreover, Mres is uncommon in Campylobacter isolates from cattle (between 0% and 6%). Beef was therefore left out of further analysis. For pork at retail, a high variation in the prevalence of Campylobacter has been reported within EU; but generally the prevalence is <10%, and the isolates are often Mres. EU data indicate that poultry meat harbor a high prevalence of Campylobacter (more more than 10%) with Mres at prevalence ranging from 0% to 8%. According to the exposure model - that included origin of meat as well as consumption patterns - most human cases of Mres campylobacteriosis (157 out of 186) was ascribed to imported meat. Only seven cases could be explained by veterinary usage of macrolides in Danish pigs. In general, human cases of campylobacteriosis are self-limiting, and it is questionable whether there is any excess risk related to infection with Mres Campylobacter compared to sensitive Campylobacter. In conclusion, the risk associated with veterinary use of macrolides in Danish pigs for the human health of Danes seemed to be low.

In Denmark, it was agreed to lower the Salmonella prevalence in pork to 1.2% before the end of 2006. The current control did not seem to be sufficient to attain this goal. Therefore, four alternatives to the existing Danish control strategy for Salmonella in pork were compared in a cost-benefit analysis: (1) hot-water decontamination of all pigs at slaughter, (2) sanitary slaughter of pigs from herds with high levels of Salmonella, (3) use of home-mixed feed in herds with slaughter pigs and (4) use of acidified feed for slaughter pigs. The data originated from official statistics, published papers as well as expert opinion. The partial cost-benefit analysis was restricted to slaughterhouses affiliated with the Danish Meat Association and Danish human cases ascribable to pork from these slaughterhouses. Only hot-water decontamination was socio-economically profitable. Hot-water decontamination had a net present value over 15 years of 3.5 million euros. For sanitary slaughter the net present value was - 43.6 million euros, for home-mixed feed it was - 262.3 million euros and for acidified feed it was - 79.9 million euros. For all alternatives the costs were born solely by the pig sector, whereas primarily the consumers and public authorities received the benefits. The conclusions were robust in sensitivity analyses.

A pilot study was carried out on a Danish swine farm infected with multi-resistant Salmonella Typhimurium DT104 (MRDT104). We aimed to (1) investigate to which degree the decline of Escherichia coli and Salmonella in swine slurry applied to farmland depended on the application method; (2) estimate the survival times of E. coli and Salmonella in the soil surface following deposition of naturally contaminated pig slurry; and (3) simulate survival of Salmonella in different infection levels using E. coli data as input estimates. Slurry was deposited by four different methods: (1) hose applicator on black soil followed by ploughing and harrowing; (2) hose applicator on black soil followed only by harrowing; (3) hose applicator on a field with winter-wheat seedlings without further soil treatment; (4) slurry injector on a field with winter-wheat seedlings without further soil treatment. E. coli and Salmonella could not be detected at all in soil following treatment 1. Following the other treatments, E. coli was not detected in soil samples after day 21 and Salmonella was no longer detected after day 7. Simulation results showed that clinical (4 log CFU g(-1)) and sub-clinical Salmonella levels (2500 CFU g(-1)) would fall below the detection limit within 10 or 5 days, respectively. Analysis of samples from 62 Danish MRDT104-infected swineherds showed that nearly 75% of these herds had low levels of MRDT104 (< 10 CFU g(-1)) in their slurry. Our results show that ploughing and harrowing of soil amended with contaminated pig slurry was an effective means to reduce environmental exposure to E. coli and Salmonella on this clay-soil farm.

Infection with Salmonella Typhimurium is seldom associated with clinical disease in pigs. However, control is important as the public is concerned about the human health impact. The producers, the abattoirs and the authorities are interested in implementing procedures to mitigate this risk. To evaluate the effect of different procedures, a stochastic risk model was developed to simulate the prevalence of Salmonella infection during the production process from the live pig on the farm, to the final carcass. This paper describes the model and findings of simulating different control scenarios. The variables with maximum effect on the Salmonella prevalence on the final carcass were (1) number of herds with a high prevalence of Salmonella, (2) singeing efficiency, (3) contamination and cross-contamination at degutting and (4) cross-contamination during handling. However, improvement of any single factor in isolation had a limited impact upon the level of contamination. The largest reduction was observed when several factors were improved concurrently.

Biosecurity measures are important for the herd's protection against diseases and also to provide nationwide protection against the introduction of exotic diseases. In this paper, we describe the farmers' choices and routines regarding biosecurity in Danish fattening herds. Overall, 116 Danish swine fattening herds in three areas of different pig density were interviewed. Of these herds, 78% purchased weaners from one sow herd only, whereas 10% purchased from >5 sow herds during 1 year. Large herds (>500 finishers) purchased weaners more often than smaller herds (< or =500 finishers). Only two swine producers purchased weaners from a market. Almost all herds (95%) received weaners from one sow herd at one time, and only one herd received from >5 sow herds in one batch. Twenty-one percent did not use an effective barrier between the loading area and the stables when delivering pigs for slaughter. Entry rooms (in which clothing and boots are changed) were common at the farm, and the numbers of visitors were generally low (<10 visitors a year). Factor analysis was performed to find underlying structures of the biosecurity measures in the herd; four factors were chosen (eigenvalue > 3.10). A site scoring high on factor 1 was a large SPF herd, which received weaners from a single source, had biosecurity requirements for the transport vehicles, and had a high level of biosecurity for visitors. A site scoring high on factor 2 was a multi-site farm, which had personnel working on more than one of the sites, only received weaners from one sow herd, had delivering herds placed close to the participating site, and transported animals themselves. A site scoring high on factor 3 was a site which hired commercial transport for slaughter, was situated far from the abattoir and had a high level of biosecurity when loading pigs. A production site scoring high on factor 4 was a large site, which used all-in/all-out management, washed and disinfected between each group, and purchased many weaners.

Low piglet weight at weaning implies a loss of income for the farmer and might influence the welfare of the affected animals negatively. The objective of our cohort study was to identify risk factors in the farrowing section associated with average daily weight gain (ADG) of piglets from birth to weaning. The study was done in 3 Danish farrow-to-finish herds and included 581 sows, 277 pens, 814 farrowings, and 8241 piglets. The data were analysed with a linear mixed model where the response was ADG, and sow and litter were random effects. Piglet treatments for arthritis (-38 g per day), diarrhoea (-8 g per day) and other infections (-21 g per day) were the major infectious contributors to lower ADG. Forelimb-skin abrasions on a piglet (-5 g per day), weak pasterns of sows on concrete slats (-34 g per day), suckling a sow with poor milking 3 weeks after farrowing (-14 g per day), low birth weight (-8.4 g per day per 100 g), male compared to female (-4 g per day) also were associated with lower ADG in the suckling period.

In Denmark, a national serological surveillance-and-control programme for Salmonella in pigs has been in operation since 1995. The programme is based on the Danish mix-ELISA and uses double testing (two ELISA-wells used per sample) of meat-juice samples taken in relation to slaughter. All herds are classified monthly into one of the three levels; the classification is based on the percentage of positive serological results in the previous 3 months. In connection with evaluation of the programme in 2001, we investigated whether single testing (testing in one well only) could be expected to be sufficiently precise compared to double testing. Data from the year 2000 were used, and mathematical modelling. Single testing was simulated by randomised selection of one of the two results in the double testing. A slight increase in the prevalence of Salmonella-positive samples (1.02-1.09 times more through the four quarters of the year 2000) was found in the simulated single testing, as compared to the double testing. Around 0.5% of the herds would be allocated to another herd level in single testing-almost equal numbers one level up and one level down. No herd being seronegative in double testing would be allocated to levels 2 or 3 (herds with >40 or >70%, respectively, serological reactors) in single testing. The prevalence of "false-positive" diagnoses (positive in single testing and negative in double testing) and inversely defined "false-negative" diagnoses varied from 4.2 to 8.7% and from 3.2 to 4.5%, respectively, through the four quarters of the year 2000. The probability of allocating a herd to a wrong level due to sampling error was on the average 6.2 (varying from 1.66 to over 100) times higher than the probability of allocating a herd to a wrong level due to the test inaccuracy introduced by going from double to single testing. This is, however, an average; a herd with a true prevalence close to one of the level border cut-offs (40 and 70% weighted seroprevalence, respectively) would have a higher risk of being allocated to a wrong level than a herd with a true prevalence far from the level border cut-offs. The results are based on the current Danish sample sizes in the surveillance scheme, which implies that 60, 75 or 100 samples are taken annually in a herd, depending on its size. Other sample sizes would produce other results.

A retrospective longitudinal study of metritis was conducted in Denmark on data collected during 1993-1994. Data on herd size, breed, parity, and treatment of disease were obtained from the Danish Cattle Database. Management and production-facility data were collected using a questionnaire, conducted as a telephone interview in 1994. The study included 2144 herds from three regions in Denmark (102,060 cows). Herd-level variables included were: herd size, housing, flooring, grazing, calving measures, and calving supervision. Cow-level variables were: parity, breed, calving season and whether the cow had been treated by a veterinarian for dystocia or the diseases: retained placenta, reproductive disease, ketosis, milk fever, or dry cow mastitis. Marginal multivariable logistic-regression analyses were performed. The cow with highest odds of metritis was a first or greater than or equal to third parity cow, of large breed, that calved during November-April, in a zero-grazing herd. The cow had been treated for dystocia, retained placenta, and at least one other reproductive disease, but not for ketosis.

The Danish surveillance-and-control program for Salmonella in slaughter pigs was introduced in 1995. The key element of the program is a quick and correct identification of herds with high seroprevalence. After 5 years, the classification scheme was evaluated--and a revision was made. Data from two Salmonella screenings including a total of 1902 slaughter pig herds were used. For each herd, information was available on Salmonella status based on both microbiology and serology. Based on analyses of these data, suitable changes in the scheme were identified and their effect estimated by use of data from the Danish Salmonella Database including all herds in 2000. The classification scheme has been adjusted on the following points. (1) The sampling has been simplified into 60, 75, or 100 samples per herd per year depending on herd size. This means more-precise estimates for the seroprevalence among smaller herds. (2) Herds with an annual kill or=index 40, and the limit between Levels 2 and 3 to >or=index 70. If the Danish swine producers are interested, a Level 0 may be introduced (consisting of seronegative herds as an indication of a negligible Salmonella prevalence). The classification scheme was introduced in August 2001.

Salmonella Typhimurium DT104 (DT104) is unwanted in products for human consumption due to its antibiotic resistance and ability to cause disease. We intended to set up an improved monitoring and management program to aid in deciding when to use pork contaminated with DT104 for production of sausages without jeopardizing consumer safety. We started by carrying out two assessments of the risk for human health associated with consumption of sausages produced by: (1) Danish pork from average slaughter days; (2) imported pork (IMP) with average prevalence of DT104. The assessments showed that, if Salmonella is present, it is usually in lower numbers (< or =50 per 400 cm(2) surface). Additionally, during processing, the numbers will be reduced by at least 2 log-units. In Danish (DK) pork, DT104 constitutes 0.2-1.0% of the Salmonella isolates reported, while in imported pork (IMP), 18%. We estimated that out of one million, 25 g servings of DK dry-cured sausages, up to two DT104 bacteria could be found in each of 245 servings. Out of one million servings of 25 g IMP dry-cured sausages, up to two DT104 bacteria would occur in each of 19,260 servings.

To study how routinely recorded data (also called "register data") might be used in disease monitoring on a regional or national level, a database for bovine virus-diarrhoea virus (BVDV) was made from existing databases, covering the period January 1995-November 1999. This paper includes a general description of the database, including basic statistics for selected variables. Information was largely complete for cattle herds in the milk-recording scheme (MRS), but only partly available for other herds. A methodology was developed to identify when and how a herd initially was infected. For most herds, it was possible to determine when and how BVDV first was introduced. Among the infected herds, most were already infected by the start of the study. BVDV had been present in 40% of the MRS herds and in 9% of the non-MRS herds. In the MRS herds, most new infections were associated with a dam that had been present in the same herd during gestation. Among the non-MRS herds, most new infections were associated with movement of a persistently infected animal. The monthly number of newly infected herds is presented; it is seen that the incidence declined substantially during the study period.

In a cross-sectional study on milk samples from 1155 cows from 22 Danish dairy herds, selected risk factors for paratuberculosis were identified. The diagnostic procedure used was an indirect enzyme-linked immuno-sorbent assay (ELISA) to detect antibodies against Mycobacterium avium subsp. paratuberculosis. A sample was considered test-positive if it had a corrected optical density >/=0. 025 (test sensitivity 71.4% and test specificity 89.7%). Of the 1155 samples, 8.8% (102/1155) were test-positive, and 19 out of the 22 dairy herds had >/=1 test-positive cows. The significant risk factors in a multiple logistic regression analysis were: Jersey versus large breeds, high parity versus low parity, the first month after calving versus other months of lactation, and a large herd size compared to a small herd size. The highest probability (37-38%) of a positive test was observed among older cows (parity >4) and tested within the first month after calving (irrespective of breed). The lowest probability (2%) of a positive test-result was observed among first parity, large-breed cows tested before calving or later than one month after.