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Brazil is the fourth largest producer and exporter of pork in the world, standing out for its potential to increase pig production nationwide. Among the diseases that can severely compromise trade relations and cause significant losses in pig production in Brazil, Classical Swine Fever (CSF) is notable for being a highly contagious viral disease with high potential for spreading among domestic and wild pigs, wild boars, and peccaries. The present study aimed to identify high-risk regions for CSF in Brazil through spatial, temporal, and spatiotemporal analyses from 2000 to 2023. During this period, 3189 cases of CSF were detected, all reported exclusively in states within the CSF non-free zone. The Northeast region accounted for 90.31 % (2880/3189) of the total CSF cases, with Ceará reporting the highest number of cases at 1475 (46.25 %), of which 810 were reported in 2018 alone. The North region accounted for 9.69 % (309/3189) of the total cases, with the states of Pará and Amapá being the only ones to report cases of the disease. Temporal trend analysis identified an increase in Piauí (Annual Percentage Change [APC]: 25.58 %), Alagoas (APC: 28.01 %), and Ceará (APC: 17.99 %), a decreasing trend for Pernambuco (APC: 24.49 %), Paraíba (APC: 19.35 %), and Rio Grande do Norte (APC: 11.85 %), and stability in Maranhão (APC: 0.17 %), Pará (APC: 1.61 %), and Amapá (APC: 15.52 %). The spatiotemporal analysis identified the formation of two high-risk clusters: the primary cluster occurred in the Northeast region, specifically in the states of Ceará, Piauí, Rio Grande do Norte, Paraíba, Pernambuco, and Alagoas, between 2018 and 2019, with a total of 1556 CSF cases and Relative Risk (RRs) of 120.02. The secondary cluster was formed by the states of Rondônia, Acre, Amazônia, Roraima, Pará, Amapá, and Mato Grosso, located in the North and part of the Midwest region, for the year 2009, with a total of 309 cases and an RRs of 29.89. In conclusion, the Northeast region is considered high-risk for the emergence of new CSF cases, highlighting the states of Ceará and Piauí, which can be considered important sources of CSF virus spread to other Brazilian states, alerting authorities to the need for disease control actions. [ABSTRACT FROM AUTHOR]

Oral vaccination is one of the most effective interventions for disease control in wildlife. As a result of the recent global reemergence of African swine fever and ongoing classical swine fever and animal tuberculosis, oral vaccination of Eurasian wild boar (Sus scrofa) receives increased interest. Several baits for wild boar and feral pigs have been described, but developing more stable and personalized formulations is important. This paper proposes a new bait formulation primarily composed of corn flour, piglet feed, sugar, and honey as a binder to obtain improved elasticity. The bait consists of a matrix with no protective coats, has a hemispherical shape (ø 3.4 ×1.6 cm), and displays an anise aroma and blue color. The color and aroma did not affect bait choice by wild boar, while bait coloring contributed to avoid consumption by non-target species (corvids). Baits with the new formulation were significantly more resistant to humidity and high temperatures than previous versions. Simulations suggest that baits with the new formulation are elastic enough to resist impacts from a maximum altitude of 750 m. Thus, the new bait prototype solves several problems of previous bait formulations while keeping a format that can be selectively consumed by piglets and adult wild boar. [ABSTRACT FROM AUTHOR]

Animal disease outbreaks, such as the recent outbreak of African Swine Fever in 2018, are a major concern for stakeholders across the food supply chain due to their potential to disrupt global food security, cause economic losses, and threaten animal welfare. As a result of their transboundary nature, discussions have shifted to preventive measures aimed at protecting livestock while ensuring food security and safety. Emergency assistance has been a critical response option during pandemics. However, this may not be sustainable in the long run because the expectation of government bailout may encourage risk taking behaviours. Our hypothesis is that an indemnity policy that is conditioned on showing biosecurity practices would increase compliance and reduce government expenditure during disease outbreaks. We developed and launched a survey from March to July 2022 targeted at swine producers across the US. From the survey, we examined livestock farmers' attitudes and intentions regarding biosecurity investment and assessed their attitudes towards the purchase of livestock insurance and reporting suspected infected livestock on their farm. We used a partial proportion odds model analysis to examine the model. Our analysis revealed that intention to call a veterinarian, trust in government agencies and risk perception of farmers were instrumental in the willingness to self-invest in biosecurity, purchase livestock insurance, and promptly report infected livestock on their farms. This provides evidence that biosecurity compliance would increase if indemnification was tied to a demonstration of effort to adopt biosecurity practices. We also show that individuals who have been in the industry for a longer period may become complacent and less likely to report outbreaks. Farmers with a higher share of income from their production operations bear a greater risk from their operational income and are more willing to report any suspected infections on their farms. The data suggest that motivating the willingness of farmers to invest in biosecurity while overcoming cost concerns is achievable. [ABSTRACT FROM AUTHOR]

Classical swine fever (CSF) re-emerged in Gifu Prefecture, central Japan, in September 2018 and is currently widespread in wild boar populations. Due to its widespread in wild boars, an oral mass vaccination strategy was initiated in March 2019, employing a commercial bait vaccine that is a live attenuated vaccine. To enhance the effectiveness of oral vaccination, it is crucial to determine the vaccine's effective spatial range. This understanding is essential for devising a comprehensive vaccination strategy, which should also include a preliminary investigation of wild boar habitats before vaccination. This study aimed to estimate the effective range of oral vaccination for wild boars against CSF by analyzing the geographical relationship between immune wild boars and vaccination points within the vaccination areas in Gifu Prefecture. This study utilized oral vaccination data from April 2021 to March 2022. The prevalence of CSF infections in wild boars remained below 5% in this period, suggesting limited disease transmission and immune wild boars were considered to be induced by the effect of vaccination. Two vaccination campaigns were conducted during this period, with almost 2000 vaccination points each. To investigate the factors associated with the intensity (i.e., density) of immune wild boar, the nearest distances to a vaccination point and to a susceptible wild boar were evaluated as explanatory variables. The Rhohat procedure and point process model were utilized to analyze the relationship between the intensity of immune wild boars and the explanatory variables. The point process model revealed a significant decrease in the intensity of immune wild boars when the distance from the nearest vaccination point exceeded 500 m, indicating that the effective spatial range of bait vaccination is within 500 m of the vaccination point. Although the distance to the nearest susceptible animal did not show significance in the model, Rhohat plots indicated that the intensity of immune wild boars decreased at distances greater than 1200 m from the nearest susceptible wild boar. This finding highlights the importance of investigating susceptible wild boar populations within a range of at least 1200 m from a vaccination point before implementation. The present study revealed the effective range of oral vaccination for wild boars against CSF and indicated the importance of investigating susceptible wild boar habitats around vaccination points before the implementation of vaccination. These findings may help improve the effectiveness of oral vaccinations. ● Classical swine fever (CSF) re-emerged in Japan in September 2018. ● CSF has spread to domestic pigs and wild boars. ● Oral vaccination has also been implemented in wild boars. ● The effective spatial range of oral vaccination was estimated. ● The intensity of immune wild boars increased within 500 m of the vaccination point. [ABSTRACT FROM AUTHOR]

Abstract Pigs in Lao People's Democratic Republic are important for income and food security, particularly in rural households. The majority of pigs are reared in smallholder systems, which may challenge the implementation of any disease control strategies. To investigate risk factors for pig production diseases in such farming systems in the country a serological survey was conducted during 2011. A total of 647 pigs were sampled, accounting for 294 households in Luang Prabang and 353 in Savannakhet province representing upland and lowland, respectively. The results demonstrated that pigs in Lao PDR had antibodies against erysipelas (45.2%), CSF (11.2%), PRRS (8.6%), FMD O (17.2%) and FMD Asia 1, (3.5%). Differences in the housing systems influenced disease risk, for example, penned pigs had reduced odds of FMD and CSF, compared to those in scavenger systems. Pigs owned by farms using a sanaam (a communal area where pigs are kept for some time of the year) had 3.93 (95% confidence interval (CI): 1.09–14.7) times the odds of having pigs seropositive for FMD. Farms on which sudden piglet deaths had been experienced were more likely to have pigs seropositive for FMD O and erysipelas. These diseases constrain the development of village farming and the wider livestock industry due to their impact on productivity and trade. Vaccination coverage for FMD and CSF was low and there was a lack of national funding for livestock disease control at the time of the study. Further investigation into sustainable low-cost control strategies for these pathogens is warranted. [ABSTRACT FROM AUTHOR]

Abstract Classical swine fever (CSF) is a viral infectious disease of swine with significant economic impact in the affected countries due to the limitation of trade, culling of infected animals and production losses. In Latin America, CSF is endemic in several countries including Ecuador, Bolivia, Brazil and Peru. Since 2010, the National Veterinary Services of Peru have been working to better control and eradicate the disease with an intensive vaccination program. The aim of this study was to evaluate the effectiveness of the vaccination program and determine which factors are still contributing to the persistence of the disease in certain regions of Peru. We integrated the data from the vaccination campaign, the live pig movement network and other socioeconomic indicators into a multilevel logistic regression model to evaluate their association with CSF occurrence at district level. The results revealed that high vaccination coverage significantly reduces the risk of CSF occurrence (OR = 0.07), supporting the effectiveness of the vaccination program. Districts belonging to large and medium pig trade network communities (as identified with walktrap algorithm) had higher probability to CSF occurrence (OR = 2.83 and OR = 5.83, respectively). The human development index (HDI) and the presence of a slaughterhouse in the district was also significantly associated with an increased likelihood of CSF occurrence (OR = 1.52 and OR = 3.25, respectively). Districts receiving a high proportion of the movements from districts that were infected in the previous year were also at higher risk of CSF occurrence (OR = 3.30). These results should be useful to guide the prioritization of vaccination strategies and may help to design other intervention strategies (e.g., target education, movement restrictions, etc.) in high-risk areas to more rapidly advance in the eradication of CSF in Peru. [ABSTRACT FROM AUTHOR]

The objective of this study was to trial point of truth calibration (POTCal) as a novel method for disease prioritisation. To illustrate the application of this method, we used a previously described case-study of prioritisation of exotic diseases for the pig industry in Australia. Disease scenarios were constructed from criteria which described potential impact and pig-producers were asked to score the importance of each scenario. POTCal was used to model participants’ estimates of disease importance as a function of the criteria, to derive a predictive model to prioritise a range of exotic diseases. The best validation of producers’ estimates was achieved using a model derived from all responses. The highest weighted criteria were attack rate, case fatality rate and market loss, and the highest priority diseases were the vesicular diseases followed by swine fevers and zoonotic encephalitides. Comparison of results with a previous study in which probabilistic inversion was used to prioritise diseases for the same group of producers highlighted differences between disease prioritisation methods. Overall, this study demonstrated that POTCal can be used for disease prioritisation. An advantage of POTCal is that valid models can be developed that reflect decision-makers’ heuristics. Specifically, this evaluation of the use of POTCal in animal health illustrates how the judgements of participants can be incorporated into a decision-making process. Further research is needed to investigate the influence of scenarios presented to participants during POTCal evaluations, and the robustness of this approach applied to different disease issues (e.g. exotic versus endemic) and production types (e.g. intensive versus extensive). To our knowledge, this is the first report of the use of POTCal for disease prioritisation. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

Be-FAST is a computer program based on a time-spatial stochastic spread mathematical model for studying the transmission of infectious livestock diseases within and between farms. The present work describes a new module integrated into Be-FAST to model the economic consequences of the spreading of classical swine fever (CSF) and other infectious livestock diseases within and between farms. CSF is financially one of the most damaging diseases in the swine industry worldwide. Specifically in Spain, the economic costs in the two last CSF epidemics (1997 and 2001) reached jointly more than 108 million euros. The present analysis suggests that severe CSF epidemics are associated with significant economic costs, approximately 80% of which are related to animal culling. Direct costs associated with control measures are strongly associated with the number of infected farms, while indirect costs are more strongly associated with epidemic duration. The economic model has been validated with economic information around the last outbreaks in Spain. These results suggest that our economic module may be useful for analysing and predicting economic consequences of livestock disease epidemics. [ABSTRACT FROM AUTHOR]

Classical swine fever virus (CSFV) is a highly infectious disease of pigs. It has had significant impacts on East Nusa Tenggara, eastern Indonesia since its introduction in 1997. In spite of its importance to this region, little is known about its seroprevalence and distribution, and pig-level and farmer-level factors that may have an impact on the serological status of an individual pig. To address this knowledge deficit, a cross-sectional seroprevalence survey was conducted in 2010 involving 2160 pigs and 805 farmers from four islands in the region. Farmer questionnaires and pig record forms were used to collect data about the farmers and pigs surveyed. Blood was collected from each pig to determine its CSFV serological status. Apparent and true prevalence were calculated for each island, district, subdistrict, and village surveyed. CSFV serological status was used as an outcome variable in mixed effects logistic regression analyses. Overall true CSFV seroprevalence was estimated at 17.5% (lower CI 16.0%; upper CI 19.5%). Seroprevalence estimates varied widely across the islands, districts, subdistricts, and villages. Manggarai Barat, a district on the western end of Flores Island, contained pigs that were positive for antibody to CSFV. This result was unexpected, as no clinical cases had been reported in this area. Older pigs and pigs that had been vaccinated for CSFV were more likely to test positive for antibody to CSFV. The final multivariable model accounted for a large amount of variation in the data, however much of this variation was explained by the random effects with less than 2% of the variation explained by pig age and pig CSFV vaccination status. In this study we documented the seroprevalence of CSFV across four islands in East Nusa Tenggara, eastern Indonesia. We also identified risk factors for the presence of antibody to CSFV. Further investigation is needed to understand why clinical CSFV has not been reported on the western end of Flores Island, and to identify additional risk factors that explain CSFV serological status to inform disease control strategies. [ABSTRACT FROM AUTHOR]

Knowledge of live animal movement through markets and from farm-to-farm is needed to inform strategies for control of trans-boundary animal diseases (TADs) in south-east Asia, particularly due to consumer preference for fresh meat. In eastern Indonesia a TAD of principal interest for control is classical swine fever (CSF) due to its impacts on smallholder farmers. Pig movement is considered a contributor to failure of current CSF control efforts but pig movement patterns are not well understood. This study investigated movement of live pigs in West Timor, Flores and Sumba islands during 2009–2010, with the aim of informing CSF control policies for Nusa Tenggara Timor province. A market survey of 292 pig sellers and 281 pig buyers across nine live pig markets and a farmer survey across 18 villages with 289 smallholder farmers were conducted and information collected on pig movements. The data obtained was used for social network analysis (SNA) on formal (via a market) and informal (village-to-village) movements using information on trading practices, source and destination locations, and the number of pigs being moved. Both inter- and intra-island movements were identified, however inter-island movement was only observed between Flores and Sumba islands. West Timor and Sumba had highly connected networks where large numbers of villages were directly and indirectly linked through pig movement. Further for West Timor, both formal and informal pig movements linked the capital Kupang, on the eastern end of the island to the western districts bordering East Timor connecting all five districts and demonstrating that informal movement transports pigs over distances similar to formal movement on this island. Sumba had a higher potential for pigs to move to a greater number of sequential locations across the entire island. Flores was found to have a more fragmented network, with pig movements concentrated in its eastern or western regions, influenced by terrain. Markets were confirmed as high-risk locations for the introduction and spread of disease, having over 20 contacts (based on in- and out-degree values) depending on operational day. Villages considered high-risk for CSF spread via informal movements were characterised by higher volume of pig exits and/or linkage to higher numbers of other villages. These findings demonstrate that informal movement (often related to cultural practices) can be extensive and the high level of connectivity dictates that control strategies for CSF and other highly transmissible diseases must be formulated at the provincial level and in collaboration with East Timor. [ABSTRACT FROM AUTHOR]

Pig farming is a common practice among smallholder farmers in Nusa Tenggara Timur province (NTT), eastern Indonesia. To understand their production systems a survey of smallholder pig farmers was conducted. Eighteen villages were randomly selected across West Timor, Flores and Sumba islands, and 289 pig farmers were interviewed. Information on pig management, biosecurity practices, pig movements and knowledge of pig health and disease, specifically classical swine fever was collected. The mean number of pigs per herd was 5.0 (not including piglets), and total marketable herd size (pigs ≥ two months of age) did not differ significantly between islands ( P = 0.215). Chickens (71%) and dogs (62%) were the most commonly kept animal species in addition to pigs. Pigs were mainly kept as a secondary income source (69%) and 83% of farmers owned at least one sow. Seventy-four percent (74%) of pigs were housed in a kandang (small bamboo pen) and 25% were tethered. Pig feeds were primarily locally sourced agricultural products (93%). The majority of farmers had no knowledge of classical swine fever (91%) and biosecurity practices were minimal. Forty-five percent (45%) reported to consuming a pig when it died and 74% failed to report cases of sick or dead pigs to appropriate authorities. Sixty-five percent (65%) of farmers reported that a veterinarian or animal health worker had never visited their village. Backyard slaughter was common practice (55%), with meat mainly used for home consumption (89%). Most (73%) farmers purchased pigs in order to raise the animal on their farm with 36% purchasing at least one pig within the last year. Predominantly fattener pigs (34%) were given as gifts for celebratory events, most commonly for funerals (32%), traditional ceremonies (27%) and marriages (10%). For improved productivity of this traditional low-input system, research incorporating farming training and improved knowledge on pig disease and biosecurity needs to be integrated with greater access to extension services. [ABSTRACT FROM AUTHOR]

Classical swine fever is a disease that infects wild boars and pigs and had a significant negative economic impact on the swine industry. Oral vaccination is an effective method for controlling classical swine fever. However, information on oral vaccination program has been limited, and its efficiency has not been clarified in Japan. The purpose of this study was to determine the seasonal variation in factors affecting the ingestion of oral vaccines by wild boars. The Gifu Prefecture oral vaccination program was initiated in March 2019, and by February 2021, six seasonal programs had been conducted. We investigated the relationship between the ingestion of oral vaccines by wild boar and pre-baiting, vaccination event, environmental and topographical factors in six vaccination events in three seasonal programs (summer 2019, winter 2019–2020, and spring 2020). This study showed that pre-baiting and the repeated vaccination events were more important factors for the ingestion of oral vaccines by wild boars than topographical and land use factors. Thus, it is a possibility that habitat selection of wild boars is irrelevant in increasing the feeding rate of wild boars on oral vaccines. Consequently, wildlife managers should not only conduct pre-baiting and repeated vaccination events, but also identify areas where wild boars are more abundant immediately prior to oral vaccination programs. To increase the effectiveness of vaccination, it is important for wildlife managers to first implement estimating wild boar density in their habitat areas, followed by efficient oral vaccination programs depending on their densities. Thereafter, they should specifically consider the influence of ingestion by other species and differences in feeding rates by age class. [ABSTRACT FROM AUTHOR]

Pig farming in Ecuador represents an important economic and cultural sector, challenged by classical swine fever (CSF). Recently, the National Veterinary Service (NVS), has dedicated its efforts to control the disease by implementing pig identification, mandatory vaccination against CSF and movement control. Our objective was to characterise pig premises according to risk criteria, to model the effect of movement restriction strategies and to consider the temporal evolution of the network. Social network analysis (SNA), SIRS (susceptible, infected, recovered, susceptible) network modelling and temporal analysis were used. The network contained 751,003 shipments and 6 million pigs from 2017 to 2019. Participating premises consisted of 144,118 backyard farms, 138 industrial farms, 21,337 traders and 51 markets. The 10 most influential markets, in the Andean highlands, received between 500 and 4600 pigs each week. The 10 most influential traders made about 3 shipments with 17 pigs per week. Simulations without control strategy resulted in an average CSF prevalence of 14.4 %; targeted movement restriction reduced the prevalence to 7.2 %, while with random movement restriction it was 13 %. Targeting the top 10 national traders and markets and one of the high-risk premises in every parish was one of the best strategies with the surveillance infrastructure available, highlighting its major influence and epidemiological importance in the network. When comparing the static network with its temporal counterpart, causal fidelity (c = 0.62) showed a 38 % overestimation in the number of transmission paths, also traversing the network required 4.39 steps, lasting approximately 233 days. In conclusion, NVS surveillance strategies could be more efficient by targeting the most at-risk premises, and in particular, taking into account the temporal information would make the risk assessment much more precise. This information could contribute to implement risk-based surveillance reducing the time to eradicate CSF and other infectious animal diseases. • We used network modelling to simulate classical swine fever control strategies. • 75 % of Ecuadorian pig premises made one incoming or outgoing movement a year. • Target selection of high risk-nodes contributes to implement risk-based surveillance. • 10 traders were as influential as 53 markets in the transmission over the network. • Causal fidelity showed an overestimation of 38 % in the transmission paths. [ABSTRACT FROM AUTHOR]

Foot-and-mouth disease (FMD) is a highly contagious viral disease of domesticated and wild ruminants and pigs that causes enormous economic losses through morbidity, mortality, and trade restrictions. Although the disease is endemic in Pakistan, seasonal outbreaks occur every year throughout the country. This study aimed to investigate FMD outbreaks and to identify the risk factors associated with FMD outbreaks between January and April 2019 in the Punjab province. We performed outbreak investigations (n = 64) for FMD in nine districts of the Punjab province through Divisional Disease Diagnostic Laboratories, Livestock and Dairy Development Department Punjab. Subsequently, we conducted a case-control study including 128 livestock farms (case to control ratio = 1). The data on various plausibly associated factors were collected using a structured questionnaire from each farm. The FMD outbreaks started during the month of January, culminated in February (n = 36, 56.25%) and stopped during the month of April 2019. The most common serotype was O (45.83%), followed by Asia1 (29.17%) and A (13.89%); however, some case farms had mixed infection with serotypes A and O (9.72%) and serotypes O and Asia1 (1.39%). Multivariable analysis revealed that the history of introducing a new animal with unknown FMD vaccination status in the herd (OR =11.51, 95% CI = 3.28 – 40.47), not practicing regular vaccination against FMD (OR = 20.81, 95% CI = 4.59 – 94.35), history of the visit of an animal broker (OR = 9.06, 95% CI = 2.31 – 35.61), distance of the farm to a nearby livestock farm (OR = 6.13, 95% CI = 1.39 – 27.01) and large herd size (OR = 20.79, 95% CI = 2.45 – 176.27) were significantly associated with the occurrence of FMD outbreaks in Punjab province during 2019. In conclusion, improving biosecurity measures, avoiding the introduction of animals without FMD vaccination history and regular vaccination against FMD can significantly reduce the occurrence of the disease on livestock farms in Pakistan. [ABSTRACT FROM AUTHOR]

Abstract: The analysis of epidemiological field data from monitoring and surveillance systems (MOSSs) in wild animals is of great importance in order to evaluate the performance of such systems. By parameter estimation from MOSS data, conclusions about disease dynamics in the observed population can be drawn. To strengthen the analysis, the implementation of a maximum likelihood estimation is the main aim of our work. The new approach presented here is based on an underlying simple SIR (susceptible-infected-recovered) model for a disease scenario in a wildlife population. The three corresponding classes are assumed to govern the intensities (number of animals in the classes) of non-homogeneous Poisson processes. A sampling rate was defined which describes the process of data collection (for MOSSs). Further, the performance of the diagnostics was implemented in the model by a diagnostic matrix containing misclassification rates. Both descriptions of these MOSS parts were included in the Poisson process approach. For simulation studies, the combined model demonstrates its ability to validly estimate epidemiological parameters, such as the basic reproduction rate R 0. These parameters will help the evaluation of existing disease control systems. They will also enable comparison with other simulation models. The model has been tested with data from a Classical Swine Fever (CSF) outbreak in wild boars (Sus scrofa scrofa L.) from a region of Germany (1999–2002). The results show that the hunting strategy as a sole control tool is insufficient to decrease the threshold for susceptible animals to eradicate the disease, since the estimated R 0 confirms an ongoing epidemic of CSF. [Copyright &y& Elsevier]

Abstract: 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 [1] SPF – specific pathogen free. A system in which the herds are regularly checked for freedom from a number of diseases according to the health declaration of the programme. A herd can be free from all or some of the diseases. The owner of the herd is obliged to inform the SPF company and the buyer about the health status before selling pigs and to follow a certain set of rules regarding biosecurity (Anon., 2008). 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 &y& Elsevier]

Abstract: Classical swine fever (CSF) outbreaks can cause enormous losses in naïve pig populations. How to best minimize the economic damage and number of culled animals caused by CSF is therefore an important research area. The baseline CSF control strategy in the European Union and Switzerland consists of culling all animals in infected herds, movement restrictions for animals, material and people within a given distance to the infected herd and epidemiological tracing of transmission contacts. Additional disease control measures such as pre-emptive culling or vaccination have been recommended based on the results from several simulation models; however, these models were parameterized for areas with high animal densities. The objective of this study was to explore whether pre-emptive culling and emergency vaccination should also be recommended in low- to moderate-density areas such as Switzerland. Additionally, we studied the influence of initial outbreak conditions on outbreak severity to improve the efficiency of disease prevention and surveillance. A spatial, stochastic, individual-animal-based simulation model using all registered Swiss pig premises in 2009 (n =9770) was implemented to quantify these relationships. The model simulates within-herd and between-herd transmission (direct and indirect contacts and local area spread). By varying the four parameters (a) control measures, (b) index herd type (breeding, fattening, weaning or mixed herd), (c) detection delay for secondary cases during an outbreak and (d) contact tracing probability, 112 distinct scenarios were simulated. To assess the impact of scenarios on outbreak severity, daily transmission rates were compared between scenarios. Compared with the baseline strategy (stamping out and movement restrictions) vaccination and pre-emptive culling neither reduced outbreak size nor duration. Outbreaks starting in a herd with weaning piglets or fattening pigs caused higher losses regarding to the number of culled premises and were longer lasting than those starting in the two other index herd types. Similarly, larger transmission rates were estimated for these index herd type outbreaks. A longer detection delay resulted in more culled premises and longer duration and better transmission tracing increased the number of short outbreaks. Based on the simulation results, baseline control strategies seem sufficient to control CSF in low-medium animal-dense areas. Early detection of outbreaks is crucial and risk-based surveillance should be focused on weaning piglet and fattening pig premises. [Copyright &y& Elsevier]

Abstract: Classical swine fever (CSF) is a severe multi-systemic disease that can affect both domestic pigs and wild boar. Past outbreaks in European wild boar involved high-virulent CSF virus (CSFV) strains and were mostly self-limiting. In these cases, morbidity and mortality rates were high in the affected regions. In contrast, endemic infections have been observed in several European wild boar populations in recent decades. Morbidity and mortality rates were much lower despite the fact that outbreaks were still detected via diseased or fallen animals. The virus strains involved were mostly classified as genotype 2.3 strains of moderate virulence causing age-dependent disease outcomes. The mechanisms leading to the establishment and perpetuation of endemicity are still not fully understood, but the factor “moderate virulence” seems to be of considerable importance. In this study, we aim to clarify whether the perception of declined ‘CSF severity’ could hypothetically reflect the adaptation of an initially high-virulent virus or whether this might be better explained as a misinterpretation of observations. A mechanistic eco-epidemiological model was employed to follow up a highly virulent strain of CSFV introduced into large connected wild boar populations. In the model, the virulence of the CSF virus is represented by case mortality and life expectancy after lethal infection. Allowing for small stochastic variation, these two characteristics of the virus are passed on with every new simulated infection that occurs. Model analysis revealed a decrease from high to moderate case mortality within a few years of simulated perpetuation of the virus. The resulting mortality corresponded to the level where the population average of the infectious period and the basic reproduction number of the disease were maximal. This shift in virulence was sufficient to prolong virus circulation considerably beyond the epidemic phase of the simulated outbreaks. Alternative mechanistic explanations for the decrease in disease severity in a CSF-affected wild boar population were evaluated in the light of the simulation experiments and the available epidemiological or virological evidence. In conclusion, the current virus isolates of subgroup 2.3 might be the ideally adapted variants of the CSF virus for long-term perpetuation in wildlife and indeed may have evolved (once) during past outbreaks in large populations. A repeated perception of a declining severity of disease pattern during the course of a CSF outbreak, however, favours the explanation based on monitoring and detection biases rather than repeated observation of selection against highly virulent virus during the time of virus perpetuation. [Copyright &y& Elsevier]

Abstract: Classical swine fever (CSF) outbreaks may result in huge economic losses to countries with densely populated pig areas (DPLAs). The EU minimum control measures require depopulation of infected farms, movement restrictions, zoning and surveillance (EU Minimum strategy). Emergency vaccination is authorised for DPLAs although the EU Minimum strategy plus culling in a 1-km ring around infected premises is preferred. Nonetheless, vaccination in a 2-km ring has been found equally effective as 1-km ring culling using stochastic modelling. Alternatives control measures (e.g. antiviral agents, in particular small molecule inhibitors of the CSFV replication) are being explored. Hence, the present study was set up to simulate inter-herd CSFV spread when antiviral molecules are supplemented to pig feed in a 1-km ring around infected farms. The effectiveness of the antiviral strategy for containing CSF outbreaks was compared to six other control scenarios including the EU Minimum strategy, the EU preferred policy for DPLAs and the use of 2-km ring vaccination. The InterSpread Plus model was adapted to the 2006 Belgian pig population and outbreak simulations were performed with a fast spreading CSFV strain entering a DPLA in Belgium. Four out of the seven control strategies resulted in outbreaks that were controlled by the end of the simulation period (i.e. 365 days). The distributions of the number of infected herds and the duration of the predicted outbreaks for these four control strategies were not different. This is the first report investigating CSF outbreak containment using antiviral molecules. Although antiviral supplementation was not found to perform any better than some other conventional strategies, such as pre-emptive culling and emergency vaccination, it might be worthwhile considering it further as additional tool in a response to CSF outbreaks. [Copyright &y& Elsevier]

Abstract: Early detection of the introduction of an infectious livestock disease is of great importance to limit the potential extent of an outbreak. Classical Swine Fever (CSF) often causes non-specific clinical signs, which can take considerable time to be detected. Currently, the disease can be detected by three main routes, that are all triggered by clinical signs. To improve the early detection of CSF an additional program, based on mortality data, aims to routinely perform PCR tests on ear notch samples from herds with a high(er) mortality. To assess the effectiveness of this new early detection system, we have developed a stochastic model that describes the virus transmission within a pig herd, the development of disease in infected animals and the different early detection programs. As virus transmission and mortality (by CSF and by other causes) are different for finishing pigs, piglets and sows, a distinction is made between these pig categories. The model is applied to an extensive database that contains all unique pig herds in The Netherlands, their herd sizes and their mortality reports over the CSF-free period 2001–2005. Results from the simulations suggest that the new early detection system is not effective in piglet sections, due to the high mortality from non-CSF causes, nor in sow sections, due to the low CSF-mortality. In finishing herds, the model predicts that the new early detection system can improve the detection time by two days, from 38 (27–53) days to 36 (24–51) days after virus introduction, when assuming a moderately virulent virus strain causing a 50% CSF mortality. For this result up to 5 ear notch samples per herd from 8 (0–13) finishing herds must be tested every workday. Detecting a source herd two days earlier could considerably reduce the number of initially infected herds. However, considering the variation in outcome and the uncertainty in some model assumptions, this two-day gain in detection time is too small to demonstrate a substantial effect of the new early detection system based on mortality data. But when the alertness of herd-owners and veterinarians diminishes during long CSF-free periods, the new early detection system might gain in effectiveness. [Copyright &y& Elsevier]

Abstract: Classical swine fever (CSF) outbreaks in domestic pig herds lead to the implementation of standard control measures according to legislative regulations. Ideal outbreak control entails the swift and efficient culling of all pigs on premises detected positive for CSF virus. Often all pig holdings around the detected cases are pre-emptively destroyed to exclude transmission into the neighbourhood. In addition to these measures, zones are defined in which surveillance and protection measures are intensified to prevent further distant disease spread. In particular, all movements are prohibited within standstill areas. Standstill also excludes the transport of fattened pigs to slaughter. Historical outbreaks provide evidence of the success of this control strategy. However, the extent to which the individual strategy elements contribute to this success is unknown. Therefore, we applied a spatially and temporally explicit epidemic model to the problem. Its rule-based formulation is tailored to a one-by-one model implementation of existing control concepts. Using a comparative model analysis the individual contributions of single measures to overall control success were revealed. From the results of the model we concluded that movement restrictions had the dominant impact on strategy performance suggesting a reversal of the current conceptual thinking. Additional measures such as pre-emptive culling only became relevant under imperfect compliance with movement restrictions. The importance of movement restrictions for the overall control success illustrates the need for explicit consideration of this measure when contingency strategies are being amended (e.g. emergency vaccination) and associated risks assessed. [Copyright &y& Elsevier]

Abstract: Several routes contribute to the spread of classical swine fever (CSF) during outbreaks of this disease. However, for many infected herds in recent epidemics, no route of virus introduction could be indentified. To obtain more insight into the relative importance of secretions and excretions in transmission of CSF virus, a model was developed. This model quantified the daily transmission probabilities from one infectious pig to one susceptible pig, using quantitative data on: (a) virus excretion by infected pigs, (b) survival of virus in the environment and (c) virus dose needed to infect susceptible pigs. Furthermore, the model predicted the relative contribution of secretions and excretions to this daily probability of infection of a susceptible pig. Three virus strains that differed in virulence were evaluated with the model: the highly virulent strain Brescia, the moderately virulent strain Paderborn and the low virulent strain Zoelen. Results suggest that it is highly probable that susceptible pigs in contact with Brescia or Paderborn infected pigs will be infected. For a pig in contact with a Zoelen infected pig, infection is less likely. When contact with blood is excluded, the predicted overall probability of infection was only 0.08 over the entire infectious period. The three strains differed in the relative contribution of secretions and excretions to transmission, although blood had a high probability of causing infection of a susceptible pig when in contact with a pig infected with any strain. This supports the statement that during outbreaks, control measures should ideally be based on the characteristics of the specific virus strain involved, which implies the development of strain-specific measures. [ABSTRACT FROM AUTHOR]

Abstract: The decision on which strategy to use in the control of contagious animal diseases involves complex trade-offs between multiple objectives. This paper describes a Multi Criteria Decision Making (MCDM) application to illustrate its potential support to policy makers in choosing the control strategy that best meets all of the conflicting interests. The presented application focused on the evaluation of alternative strategies to control Classical Swine Fever (CSF) epidemics within the European Union (EU) according to the preferences of the European Chief Veterinary Officers (CVO). The performed analysis was centred on the three high-level objectives of epidemiology, economics and social ethics. The appraised control alternatives consisted of the EU compulsory control strategy, a pre-emptive slaughter strategy, a protective vaccination strategy and a suppressive vaccination strategy. Using averaged preference weights of the elicited CVOs, the preference ranking of the control alternatives was determined for six EU regions. The obtained results emphasized the need for EU region-specific control. Individual CVOs differed in their views on the relative importance of the various (sub)criteria by which the performance of the alternatives were judged. Nevertheless, the individual rankings of the control alternatives within a region appeared surprisingly similar. Based on the results of the described application it was concluded that the structuring feature of the MCDM technique provides a suitable tool in assisting the complex decision making process of controlling contagious animal diseases. [ABSTRACT FROM AUTHOR]

Abstract: In 2006, total Danish pork exports were valued at €3.8 billion, 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 2km zones using live vaccine as a protective measure (vaccination-to-kill), vaccination of all weaners and finishers in the 1 or 2km 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. [Copyright &y& Elsevier]

Abstract: 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 (<5km). 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. [Copyright &y& Elsevier]

Abstract: Rapid structural change and concentration of pig production in regions with most intensive production has raised concerns about whether the risk of large-scale disease losses has increased in Finland. This paper examines the pig industry''s losses due to classical swine fever (CSF) epidemics. The work is based on economic and epidemiological models providing insights to the consequences of epidemics to infected and uninfected farms, government and meat processing. The economic analysis was carried out by use of a sector model, which simulated the recovery of pig production, starting from the recognition of the disease in the country and ending at a steady-state market equilibrium about 12 years later. The model explicitly took into account profit-maximising behaviour of producers and the effects of decrease in export demand. Epidemiological evidence suggests that under the current spatially diversified structure of Finnish pig farming and related industries, the probability of a severe disease epidemic counting dozens of infected farms is small. Even for epidemics considered large in Finland (5–33 infected farms) combined with a major reduction in export demand, the median loss was simulated to be only €19.2 million. The majority of these losses were due to loss of exports corresponding almost 20% of pig meat production in Finland. While the current structure of pig farming in Finland incurs higher production costs than the most intensive structures in Europe, it also seems to decrease the probability of ‘catastrophic’ economic losses. The results suggest that the response of export markets and the number of uninfected farms affected by preventive measures are critical to the magnitude of losses, as they can amplify losses even if only few farms become infected. [Copyright &y& Elsevier]

Abstract: A method for quantitative evaluation of surveillance for disease freedom has been presented in the accompanying paper (). This paper presents an application of the methods, using as an example surveillance for classical swine fever (CSF) in Denmark in 2005. A scenario tree model is presented for the abattoir-based serology component of the Danish CSF surveillance system, in which blood samples are collected in an ad hoc abattoir sampling process, from adult pigs originating in breeding herds in Denmark. The model incorporates effects of targeting (differential risk of seropositivity) associated with age and location (county), and disease clustering within herds. A surveillance time period of one month was used in the analysis. Records for the year 2005 were analysed, representing 25,332 samples from 3528 herds; all were negative for CSF-specific antibodies. Design prevalences of 0.1–1% of herds and 5% of animals within an infected herd were used. The estimated mean surveillance system component (SSC) sensitivities (probability that the SSC would give a positive outcome given the animals processed and that the country is infected at the design prevalences) per month were 0.18, 0.63 and 0.86, for among-herd design prevalences of 0.001, 0.005 and 0.01. The probabilities that the population was free from CSF at each of these design prevalences, after a year of accumulated negative surveillance data, were 0.91, 1.00 and 1.00. Targeting adults and herds from South Jutland was estimated to give approximately 1.9, 1.6 and 1.4 times the surveillance sensitivity of a proportionally representative sampling program for these three among-herd design prevalences. [Copyright &y& Elsevier]

Abstract: Recent history has demonstrated that classical swine fever (CSF) epidemics can incur high economic losses, especially for exporting countries that have densely populated pig areas and apply a strategy of non-vaccination, such as The Netherlands. Introduction of CSF virus (CSFV) remains a continuing threat to the pig production sector in The Netherlands. Reducing the annual probability of CSFV introduction (P CSFV) by preventive measures is therefore of utmost importance. The choice of preventive measures depends not only on the achieved reduction of the annual P CSFV, but also on the expenditures required for implementing these measures. The objective of this study was to explore the cost-effectiveness of tactical measures aimed at the prevention of CSFV introduction into The Netherlands. For this purpose for each measure (i) model calculations were performed with a scenario tree model for CSFV introduction and (ii) its annual cost was estimated. The cost-effectiveness was then determined as the reduction of the annual P CSFV achieved by each preventive measure (ΔP) divided by the annual cost of implementing that measure (ΔC). The measures analysed reduce the P CSFV caused by import or export of pigs. Results showed that separation of national and international transport of pigs is the most cost-effective measure, especially when risk aversion is assumed. Although testing piglets and breeding pigs by a quick and reliable PCR also had a high cost-effectiveness ratio, this measure is not attractive due to the high cost per pig imported. Besides, implementing such a measure is not allowed under current EU law, as it is trade restrictive. [Copyright &y& Elsevier]

Abstract: A report of the Scientific Committee on Animal Health and Animal Welfare of the European Commission (CEC, 1999.) includes recommendations for setting up monitoring programmes for classical swine fever (CSF) infection in a wild-boar population, based on the assumption that one would detect at least 5% prevalence in a CSF-infected wild-boar population. This assumption, however, is not science based. We propose an alternative method to provide evidence for a wild-boar population being free of CSF and evaluate the efficiency of a surveillance programme that was implemented in Belgium in 1998. In our study, the probability of freedom of CSF-virus was estimated based on 789 samples; these were collected from wild-boars within the surveillance programme (within the three provinces which include 95% of the Belgian wild-boar population) and examined by three diagnostics methods (antibody detection, virus detection and virus RNA detection). A Bayesian framework was used for the estimation, accounting for the diagnostic test characteristics without the assumption of the presence of a gold standard. The median probability of freedom of CSF-virus was estimated at 0.970, with a 95% credibility interval of 0.149–1.000. Independent on the choice of the prior information, the posterior distributions for the probability of freedom of CSF-virus were always skewed close to the upper boundary of 1. This represents a big gain of knowledge since we did not use any prior information for the probability of freedom of CSF-virus and took the uncertainty about the accuracy of the diagnostic methods into account. [Copyright &y& Elsevier]

Abstract: The herd sensitivity (HSe) and herd specificity (Hsp) of clinical diagnosis of an infection with classical swine fever (CSF) virus during veterinary inspection of breeding sows in a herd was evaluated. Data gathered from visits to herds during the CSF outbreak in 1997–1998 in The Netherlands were used for the analysis. Herds were visited one or more times by the same or by different veterinarians. On the basis of the veterinarians’ reports, each visit was coded as 0 (negative clinical diagnosis) or 1 (positive clinical diagnosis). The HSe for clinical diagnosis of CSF was modelled as a function of days elapsed since introduction of the virus. The moment of introduction of the CSF virus in the CSF-positive herds was unknown, so for each herd, a probability distribution for the unknown number of days since introduction was derived from serum samples collected at depopulation. The information from the reports of the veterinarians and from the test results of the serum samples at depopulation was combined in a Bayesian analysis. Data from CSF-negative herds were analysed to estimate HSp of clinical diagnosis of CSF. The HSe of clinical diagnosis was 0.5 at 37 days after virus introduction (95% CI: 31, 45) and reached 0.9 at 47 days after virus introduction (95% CI: 41, 54). The estimated herd specificity was 0.72 (95% CI: 0.64, 0.79). Dependence of HSe and HSp on characteristics of the veterinarians and the herds also was studied. Specialisation of the veterinarian significantly, although not markedly, affected the HSe. [Copyright &y& Elsevier]

Abstract: Consequences of classical swine fever (CSF) epidemics depend on the control measures, but also on the number of infected herds at the end of the high-risk period (HRP). Surveillance programmes aim to keep this number as low as possible, so the effectiveness of surveillance programmes can be measured by the number of infected herds at the end of the HRP. In this paper, an evaluation of the effectiveness of the following five Dutch CSF surveillance programmes is presented: (1) routine gross pathology of severely diseased pigs; (2) routine virological tests of tonsils of all pigs, submitted under 1; (3) daily clinical observation by the farmer; (4) periodic clinical inspection by a veterinarian; (5) leucocyte counts in blood samples from diseased animals on a herd where antimicrobial ‘group therapy’ is started. The evaluation was done by a modelling study, in which virus transmission, disease development, and actions and diagnostic tests in surveillance programmes were simulated. Also, the yearly costs of the programmes were calculated, and direct costs of CSF epidemics were related to the number of infected herds at the end of the HRP. It appeared that the current Dutch surveillance programmes, without the leucocyte counts, keep the number of infected herds at the end of the HRP below 20 with 95% probability. Leaving out the most-expensive programme of periodic inspection (12.5M€ per year) does not change this result – indicating that (for CSF surveillance) the programme could well be stopped. If the leucocyte programme, which is currently not effective due to the low sample submission rate, optimally were applied, the 95th percentile could be reduced to 10 infected herds. However, whether application is beneficial is unclear, because of uncertainty of the economic benefits due to the many expected false-positive herds each year. [Copyright &y& Elsevier]

Abstract: Clinical signs recorded in a classical swine fever (CSF)-suspect situation and the results of the subsequent post-mortem examination (PME) from swine submitted to post-mortem during the 1997–1998 CSF epidemic in the Netherlands, were presented in an experiment as anonymous cases (without knowledge of the actual infection status of the submission) to five veterinary pathologists for their judgment: CSF-suspect or non-suspect. It was presented to them in two hypothetical situations: country was free of CSF for 5 years and CSF was detected in the country 2 weeks ago. Subsequently, their judgment was compared to the gold standard (infection status of the submission on the basis of an immunofluoresence assay on tissue samples) and the sensitivity (Se) and specificity (Sp) of clinical diagnosis was estimated. Furthermore, intra- and inter-pathologist agreement on pathological diagnosis was measured. Adding information on clinical signs to information on PME resulted in a significant increase in median Se and a significant decrease in median Sp for a clinical judgment by pathologists. Also, median Se was significantly higher—and Sp significantly lower—for a clinical judgment by pathologists in a situation in which CSF was detected 2 weeks ago in the country compared to the situation in which the country had been free of CSF for 5 years. Apparently, the internal threshold of pathologists is severely adjusted depending on the actual disease situation in a country. Intra-rater agreement ranged from fair to almost perfect for a clinical diagnosis on the basis of PME. There was considerable variation between pathologists, especially if clinical diagnosis was based on the combined information on PME and clinical signs observed in the herd. Inter-rater agreement was substantial for the diagnosis based on information on PME. Inter-rater agreement was considerably lower for the diagnosis based on the combined information on PME and clinical signs observed in the herd. [Copyright &y& Elsevier]

At present, two types of vaccines against classical swine fever (CSF) virus are commercially available: E2 sub-unit marker vaccines and the conventional attenuated live C-strain vaccines. To evaluate the reduction of the horizontal virus transmission, three comparable experiments were carried out in which groups of weaner pigs (vaccinated with a marker vaccine or a C-strain vaccine) were challenged with CSF virus at 0, 7, and 14 days post-vaccination (dpv). Virus transmission was prevented totally when the challenge occurred at 14 dpv with an E2-marker vaccine (0/12 contact pigs positive in virus isolation (VI); R = 0 (0; 1.5)). At 7 dpv, transmission was reduced slightly (5/12 contact pigs positive in VI; R = 1.0 (0.3; 3.0)), whereas at 0dpv, vaccination had no effect on transmission (10/12 contact pigs positive in VI; R = 2.9 (1.5; 10.8)). In the C-strain-vaccinated pigs, no virus transmission was detected even when the challenge was performed at the same day as the vaccination (0/12 contact pigs positive in VI; R = 0 (0; 1.5)). [Copyright &y& Elsevier]

Data of the 1997–1998 epidemic of classical swine fever (CSF) in The Netherlands were analysed in survival analysis to identify risk factors that were associated with the rate of neighbourhood infections. The study population consisted of herds within 1000 m of exclusively one previously infected herd. Dates of virus introduction into herds were drawn randomly from estimated probability distributions per herd of possible weeks of virus introduction. (To confirm the insensitivity of the results for this random data-selection procedure, the procedure was repeated 9 times (resulting in 10 different datasets).) The dataset had 906 non-infected and 59 infected neighbour herds, which were distributed over 215 different neighbourhoods. Neighbour herds that never became infected were right-censored at the last date of the infectious period of the infected source herd. Neighbour herds that became empty within the infectious period or within the following 21 days due to preventive depopulation or due to the implemented buying-out programme were right-censored 21 days before the moment of becoming empty. This was done as a correction for the time a herd could be infected without being noticed as such.The median time to identified infection of neighbour herds was 2 weeks, whereas the median time to right censoring of non-infected neighbour herds was 3 weeks. The risk factors, radial distance ≤500 m, cattle present on source herd and increasing herd size of the neighbour herd were associated multivariably with the hazard for neighbour herds to become infected. We did not find an association between time down wind and infection risk for neighbour herds. Radial dispersion of CSFV seemed more important in neighbourhood infections than dispersion along the road on which the infected source herd is situated. The results of this study support the strategy of preventive depopulation in the neighbourhood of an infected herd. Recommendations are presented to adapt the applied control strategy for neighbourhood infections. [Copyright &y& Elsevier]

Risk factors associated with the occurrence of ‘neighbourhood infections’ [Epidemiology of classical swine fever. In: Truszczynski, M. (Ed.), Proceedings of the Workshop on Diagnostic Procedures and Measures to Control Classical Swine Fever in Domestic Pigs and the European Wild Boar. Pulaway, Poland, pp. 119–130] during classical swine fever (CSF) outbreaks were examined based on information collected during a CSF-epidemic, which occurred in the East Flanders Province of Belgium in 1994. The only risk factor that was associated with the occurrence of ‘neighbourhood infections’ was a kernel estimation of the intensity of neighbouring herds (P=0.055) [Interactive spatial data analysis. Pearson Education Limited, Harlow, Essex], i.e. the higher the kernel estimation, the higher the risk for the occurrence of neighbourhood infections.In a second part of the study, the likelihood for the occurrence of neighbourhood infections within an area with a 1 km radius was predicted for every Belgian pig herd, assuming that the herd was infected with CSF-virus. For the prediction of these likelihoods, the model resulting from the risk assessment was used. Finally, the predicted likelihoods were transformed into a raster map after applying a smoothing technique. As a result, different areas in Belgium of higher or lower risk for CSF-virus spread through ‘neighbourhood infections’ could be identified on the map. The areas in Belgium where CSF-outbreaks including ‘neighbourhood infections’ occurred in the past decades were all predicted by the model to be of high risk. [Copyright &y& Elsevier]

We examined the importance of pig-population density in the area of an outbreak of classical swine fever (CSF) for the spread of the infection and the choice of control measures. A spatial, stochastic, dynamic epidemiological simulation model linked to a sector-level market-and-trade model for The Netherlands were used. Outbreaks in sparsely and densely populated areas were compared under four different control strategies and with two alternative trade assumptions.The obligatory control strategy required by current EU legislation was predicted to be enough to eradicate an epidemic starting in an area with sparse pig population. By contrast, additional control measures would be necessary if the outbreak began in an area with high pig density. The economic consequences of using preventive slaughter rather than emergency vaccination as an additional control measure depended strongly on the reactions of trading partners. Reducing the number of animal movements significantly reduced the size and length of epidemics in areas with high pig density. The phenomenon of carrier piglets was included in the model with realistic probabilities of infection by this route, but it made a negligible contribution to the spread of the infection. [Copyright &y& Elsevier]

• In September 2018, classical swine fever (CSF) re-emerged in Japan. • CSF spread to both domestic pigs and wild boars. • Transmission risk from wild boar to vaccinated pig farms was estimated. • Pig farm vaccination reduced the risk of CSF transmission from wild boar. In 2018, classical swine fever (CSF) re-emerged in the Gifu Prefecture, central Japan, causing an on-going outbreak among wild boars and domestic pigs in the country. Consequently, oral vaccination for wild boar and compulsory vaccination for pig farms started in 2019. We have previously shown that, before vaccination in the Gifu Prefecture, the presence of CSF-infected wild boar near pig farms increased the risk of CSF transmission. This study aimed to re-evaluate the transmission risk from wild boars to pig farms under a vaccination program. The effectiveness of vaccination was evaluated by comparing the transmission risk estimated before and after the implementation of vaccinations. In this study, we focused on two affected areas, the Kanto (eastern Japan) and Kinki (west-central Japan) regions, in which eight of 11 infected farms were detected between the start of pig farm vaccinations and April 2021. Wild boar surveillance data from an area within a 50-km radius from the infected farms were used for analysis, consisting of 18,870 1-km grid cells (207 infected cells) in the Kanto region, and 15,677 cells (417 infected cells) in the Kinki region. The transmission rates in the post-vaccination period in the Kanto and Kinki regions were much lower than that in the pre-vaccination period in the Gifu Prefecture. The values of transmission kernels (h 0 , transmission rate at 0 km) in the Kanto and Kinki regions decreased to 1% of the transmission kernel in the pre-vaccination period. In the pre-vaccination period, the risk of infection within 300 days was almost 95 % when one infected grid cell was detected within 1 km of a pig farm. Meanwhile, in the post-vaccination period, the risk of infection within 300 days was approximately 5% when several infected cells were detected within 1 km of a pig farm. Considering the limited effect of oral vaccination for wild boar due to distribution limitations in the Kanto and Kinki regions, vaccination on pig farms may seems to have mainly reduced the transmission risk from wild boar. However, despite the implementation of vaccination, the risk of infection on pig farms remains present due to the immunity gap of weaning pigs. Therefore, strict biosecurity measures on pig farms and an appropriate vaccination program are required to prevent and control CSF spread. [ABSTRACT FROM AUTHOR]

PRRS is a viral disease characterized by increasing reproduction losses in breeding herds and worsening performance of growing pigs, which leads to a considerable economic impact. A better understanding of the differences in the infection patterns of the virus in growing pig batches would help to develop cost-effective surveillance methods and disease control and elimination programs. Therefore, field studies documenting growing pig productivity according to the patterns of wild-type-PRRSV (wt-PRRSV) detection in the field are needed. This study was conducted with the objectives to (1) characterize patterns of wt-PRRSV-1 and wt-PRRSV-2 RNA detection over time in modified-live virus (MLV)-vaccinated batches of growing pigs raised in pig-dense regions of the USA; (2) compare wean-to-finish mortality among batches of growing pigs characterized with the different patterns of wt-PRRSV-1 and wt-PRRSV-2 detection; and (3) compare wean-to-finish mortality among batches of growing pigs characterized with the different patterns of wt-PRRSV-2 detection and vaccinated with two different doses of PRRS MLV vaccine. Eighty-one batches of growing pigs were originated from PRRSV positive-stable and unstable sow farms and vaccinated with two different doses of PRRS MLV vaccine. All batches were monitored for wt-PRRSV by testing six oral fluids every three weeks from weaning to marketing. Diagnostics were conducted to detect wt-PRRSV-1 and wt-PRRSV-2 by RT-qPCR testing and ORF-5 region sequencing. K-means clustering analysis was applied to identify batches sharing similar patterns of wt-PRRSV detection over time. Regression analyses were used to compare mortality among batches of growing pigs characterized with different patterns of wt-PRRSV detection over time. Thirty-eight percent of batches were detected with wt-PRRSV-1 during the growth phase, with three different patterns of detection. Detection of wt-PRRSV-1 was not associated with significant increase on mortality. Ninety-one percent of batches were detected with wt-PRRSV-2 during the growth phase, with four different patterns of detection. Batches originated from PRRSV positive-unstable farms had highest mortality rate (p < 0.0001) and were characterized as Unstable wt-PRRSV-2 detection pattern. Batches characterized with Early wt-PRRSV-2 detection pattern had higher mortality than batches characterized by Mid, Late and No wt-PRRSV-2 detection during the growth phase (p < 0.0001). Batches with Mid wt-PRRSV-2 detection had higher mortality than batches characterized with Late wt-PRRSV-2 detection (p < 0.0124). Mortality rate of batches characterized with Unstable and Early wt-PRRSV-2 detection patterns was lower when pigs were vaccinated with two doses of PRRS MLV vaccine, compared to batches that received only one dose. Results presented in this study suggested that early wt-PRRSV exposure on pig populations was associated with higher wean-to-finish mortality. Additionally, results suggested that vaccination with two PRRS MLV doses was associated with lower mortality rate, when growing pig populations had early wt-PRRSV exposure. [ABSTRACT FROM AUTHOR]

Subclinical infections with Salmonella Typhimurium occur frequently in pigs. They constitute a risk for human salmonellosis and are difficult to control with currently available control measures. Vaccination against Salmonella Typhimurium in pigs can be an effective tool to control Salmonella infections at farm level. In the present study, the efficacy of an attenuated Salmonella Typhimurium vaccine (Salmoporc®, IDT Biologika) to control Salmonella infections in pigs was evaluated in three subclinically infected pig herds. The effect on Salmonella excretion and the number of pigs positive for Salmonella Typhimurium field and vaccine strains in ileocecal lymph nodes at slaughter were evaluated using five different vaccination strategies: 1. vaccination of sows, 2. vaccination of sows and piglets, 3. vaccination of sows and fattening pigs, 4. vaccination of piglets, 5. vaccination of fattening pigs, which were all compared to a non-vaccinated control group (experimental group 6). Each vaccination strategy was implemented in each farm, during two consecutive production cycles of the same sows. The prevalence of Salmonella Typhimurium field strain excretion was low; in total, 4% of the fecal and overshoe samples collected in the non-vaccinated control group were Salmonella Typhimurium field strain positive. The excretion of Salmonella Typhimurium field strain did not significantly differ between farms, production cycles and experimental groups. Applying vaccination in either sows and piglets, sows and fattening pigs, or in piglets only, resulted in a significantly reduced number of Salmonella Typhimurium field strain positive lymph nodes of slaughter pigs in the second production cycle, but not in the first production cycle. Vaccination of sows and piglets resulted in the most consistent reduction of Salmonella Typhimurium field strain positive lymph nodes at slaughter. The vaccine strain was detected in the lymph nodes of 13 pigs at slaughter, indicating the possible persistence of the vaccine strain until slaughter. Because of limitations in the study design, and the variability between farms and production cycles, the results of the current observational study should be extrapolated with care. Nevertheless, the results provide evidence that applying vaccination against Salmonella Typhimurium in sows and piglets (preferred), sows and fattening pigs, and piglets only can support the control of Salmonella Typhimurium infections by decreasing the prevalence of Salmonella Typhimurium field strain positive lymph nodes at slaughter. [ABSTRACT FROM AUTHOR]