Herd Status Research Articles

Evaluation of the Thuringian Bovine Johne's Disease Control Program-A Case Study.

Simple SummaryParatuberculosis, or Johne’s Disease, occurs worldwide, causing a granulomatous enteritis in ruminants. Control programs, which operate mainly on a voluntary basis, have been established in several regions. In Thuringia, a federal state of Germany, a voluntary control program was firstly established in 2003 and revised in 2008 and 2015. This study aimed at evaluating the results achieved in voluntary Johne’s Disease control in Thuringia between 2015 and 2020. By the end of 2020, a total of 67 dairy herds with approximately 33,000 dairy cows and 87 suckler herds keeping approximately 6000 cows of beef breeds were enrolled, representing 35% or 16% of the population, respectively. In affected herds, the program focused on prevalence reduction by hygienic measures to break the infection cycle, annual testing for the detection of animals shedding the infectious agent and culling of these animals. A certification pathway was established based on a testing period of 3 years without positive results, and 58 herds were certified as ‘non-suspect’ with respect to Johne’s Disease. Analyzing the annual calf mortality rate in enrolled dairy farms revealed that herds that had been certified as ‘non-suspect’ regarding Johne’s Disease had a lower calf mortality rate than herds that were not enrolled in the program.The Thuringian Johne’s Disease (JD) Control Program provides a voluntary approach to JD control in Thuringia, a federal state of Germany. The program has three objectives: reduce the level of infection when present; reduce the spread of JD to uninfected herds; and facilitate the certification and protection of herds that are non-suspect with respect to JD. The program offers pathways for the management of affected herds and for certification of herds with continuing negative tests. After the control stage (CS), a certification stage of at least 3 consecutive years with continuing negative results in the annual whole-herd test has to be passed until a herd can be certified as ‘non-suspect’ with respect to JD. This study focused on calf mortality in relation to JD herd status. In a longitudinal study, the association of annual calf mortality rate of a total of 93 dairy herds (13 ‘non-suspect’; 26 in control stage; 54 not enrolled) over 10 consecutive years with JD herd status was investigated using a generalized mixed linear model with repeated measures. Non-suspect herds had a lower calf mortality rate compared with other farms. We conclude that establishing JD control measures lowers the calf mortality rate.

Predicting Positive ELISA Results in Dairy Herds with a Preferred Status in a Paratuberculosis Control Program.

Simple SummaryIn many paratuberculosis control programs, test-negative herds are assigned a preferred herd status. This may induce the false belief that these herds are free of paratuberculosis. Hence, farmers may refrain from control measures that could prevent the spread of any undetected infections. The aim of the present study was to develop a predictive model to alert farmers with test-negative herds and a preferred status in the Dutch paratuberculosis control program if they are at an increased risk of positive ELISA results in a subsequent 30-month period. On the basis of the results of this study, we conclude that discrimination of herds with high (52%) and low (17%) risks of positive ELISA results is feasible. This might help farmers with the highest risks of future positive results to make better informed decisions regarding the need to take additional control measures to prevent the spread of any undetected Map infections.Dairy herds participating in the Dutch milk quality assurance program for paratuberculosis are assigned a herd status on the basis of herd examinations by ELISA of individual serum or milk samples, followed by an optional confirmatory fecal PCR. Test-negative herds are assigned Status A; the surveillance of these herds consists of biennial herd examinations. Farmers falsely believing that their Status A herds are Map-free may inadvertently refrain from preventive measures. Therefore, we aimed to develop a predictive model to alert Status A farmers at increased risk of future positive ELISA results. Using data of 8566 dairy herds with Status A in January 2016, two logistic regression models were built, with the probabilities of ≥1 or ≥2 positive samples from January 2017–June 2019 as dependent variables, and province, soil type, herd size, proportion of cattle born elsewhere, time since previous positive ELISA results, and the 95th percentile of the S/P ratios in 2015–2016, as explanatory variables. As internal validation, both models were applied to predict positive ELISA results from January 2019–June 2021, in 8026 herds with Status A in January 2019. The model predicting ≥1 positive sample had an area under the receiver operating characteristics curve of 0.76 (95% CI: 0.75, 0.77). At a cut-off predicted probability πc = 0.40, 25% of Status A herds would be alerted with positive and negative predictive values of 0.52 and 0.83, respectively. The model predicting ≥2 positive samples had lower positive, but higher negative, predictive values. This study indicates that discrimination of Status A herds with high and low risks of future positive ELISA results is feasible. This might stimulate farmers with the highest risks to take additional measures to control any undetected Map infections.

Capacity of a Bayesian model to detect infected herds using disease dynamics and risk factor information from surveillance programmes: A simulation study

Control programmes against non-regulated infectious diseases of farm animals are widely implemented. Different control programmes have different definitions of “freedom from infection” which can lead to difficulties when trading animals between countries. When a disease is still present, in order to identify herds that are safe to trade with, estimating herd-level probabilities of being infected when classified “free from infection” using field data is of major interest. Our objective was to evaluate the capacity of a Bayesian Hidden Markov Model, which computes a herd-level probability of being infected, to detect infected herds compared to using test results only. Herd-level risk factors, infection dynamics and associated test results were simulated in a population of herds, for a wide range of realistic infection contexts and test characteristics. The model was used to predict the infection status of each herd from longitudinal data: a simulated risk factor and a simulated test result. Two different indexes were used to categorize herds from the probability of being infected into a herd predicted status. The model predictive performances were evaluated using the simulated herd status as the gold standard. The model detected more infected herds than a single final test in 85 % of the scenarios which converged. The proportion of infected herds additionally detected by the model, compared to test results alone, varied depending on the context. It was higher in a context of a low herd test sensitivity. On average, around 20 %, for high test sensitivity scenarios, and 40 %, for low test sensitivity scenarios, of infected herds that were undetected by the test were accurately classified as infected by the model. Model convergence did not occur for 39 % of the scenarios, mainly in association with low herd test sensitivity. Detection of additional newly infected herds was always associated with an increased number of false positive herds (except for one scenario). The number of false positive herds was lower for scenarios with low herd test sensitivity and moderate to high incidence and prevalence. These results highlight the benefit of the model, in particular for control programmes with infection present at an endemic level in a population and reliance on test(s) of low sensitivity.

Establishment and application of a solid-phase blocking ELISA method for detection of antibodies against classical swine fever virus.

BackgroundClassical swine fever (CSF) is a severe infectious disease of pigs that causes significant economic losses to the swine industry.ObjectivesThis study developed a solid-phase blocking enzyme-linked immunosorbent assay (spbELISA) method for the specific detection of antibodies against the CSF virus (CSFV) in porcine serum samples.MethodsA spbELISA method was developed based on the recombinant E2 expressed in Escherichia coli. The specificity of this established spbELISA method was evaluated using reference serum samples positive for antibodies against other common infectious diseases. The stability and sensitivity were evaluated using an accelerated thermostability test.ResultsThe spbELISA successfully detected the antibody levels in swine vaccinated with the C-strain of CSFV. In addition, the detection ability of spbELISA for CSFV antibodies was compared with that of other commercial ELISA kits and validated using an indirect immunofluorescence assay. The results suggested that the spbELISA provides an alternative, stable, and rapid serological detection method suitable for the large-scale screening of CSFV serum antibodies.ConclusionsThe spbELISA has practical applications in assessing the vaccination status of large pig herds.

Biosecurity Levels and Farm Characteristics of African Swine Fever Outbreak and Unaffected Farms in Estonia—What Can Be Learned from Them?

Simple SummaryBiosecurity breaches have been shown to play a major role in the introduction and spread of African swine fever (ASF) in domestic pig populations. The aim of the study was to describe the biosecurity levels and management practices of ASF outbreak and uninfected herds and to identify potential risk factors for ASF introduction. The biosecurity score of ASF outbreak herds was significantly lower compared to uninfected herds. This may reflect general improvement in the application of biosecurity measures over time in Estonian pig farms as the data on uninfected herds were collected later, at a time when intensified official controls may have had their effect. Larger herds were more at risk of being ‘outbreak herds’ compared to smaller herds. The biosecurity parameters significantly associated with ‘outbreak herd’ status in statistical analysis were mostly related to indirect contacts with the outside farm environment. The biosecurity barriers applied in Estonian pig farms have not been sufficient to avoid the introduction of ASF and need critical evaluation and improvement. Reduction of all contacts between the farm and the external environment should be emphasized in a situation where ASF is circulating in wild boar populations close to pig farms.Risk factors related to external biosecurity have been considered to play a major role in the introduction and spread of African swine fever (ASF) in domestic pig populations. The aim of the study was to describe the biosecurity levels and management practices of ASF outbreak and uninfected herds and to identify potential risk factors for ASF introduction. Data collected from the outbreak herds during outbreak investigations and from the randomly selected uninfected herds were analyzed. The biosecurity score in ASF outbreak herds was significantly lower compared to uninfected herds. However, this may reflect general improvement in the application of biosecurity measures in pig farms over time as the data on uninfected herds were collected later, at a time when intensified official controls may have had their effect. Larger herds were more at risk of being outbreak herds compared to smaller herds. The biosecurity parameters significantly associated with the outbreak herd status in multiple correspondence analysis were mostly related to indirect contacts with the outside farm environment. The biosecurity barriers applied in Estonian pig farms have not been sufficient to avoid ASF introduction and need critical evaluation and improvement. Reduction of all contacts between the farm and the external environment should be emphasized in a situation where ASF is circulating in wild boar populations close to pig farms.

PROBLEMS OF WESTERNIZATION OF THE CONTEMPORARY RUSSIAN POLITICAL CULTURE

In 1993 Russia announced the westernization of its political system. Its main institutions were enshrined in the Constitution of the Russian Federation (democracy, republic, separation of powers, rule of law). However, the researchers note that the reform failed. Russia only simulates the transition to Western standards of life. The author of the study sets himself the task of identifying the reasons for failure in the nature of the country's political culture. Applying a dialectical and materialistic approach to the problem, the author reveals the influence of the economic system of the country, the social structure of society, imitative changes in the political system, socialization, and traditions of society on the nature of the political culture of Russia. Based on his previous research, the author introduces a number of new explanatory theories. In his opinion, the movement towards the Western model is slowed down by the administrative class which does not want to lose its dominant position. It is not ready to move to a competitive political system, in which it loses its power and turns into a bureaucracy dependent on public politicians representing society. The service intelligentsia is engaged in spreading the public consciousness that is beneficial to the administrative class. Together, they support the type of consciousness of the population that is beneficial to them. Western political ideology is spread in society by the civil intelligentsia, but its significance is not great. The majority of the population agrees with the rule of the administrative class and votes in support of it. Therefore, there is no competitive political system in Russia. The mass consciousness of Russians remains irrational, which allows them to control it with the help of symbolic actions. It retains such archaic features as herd status and infantilism. An infantile person needs a master who decides for him in which direction society will develop, organizes this development, takes care of the population. People express dissatisfaction with this master, but accept his power and obey him. The degree of westernization of Russia's political culture is still very insignificant. The author defines it as 3 points out of 10. The political culture of Russia will be westernized as competitive capitalist relations develop in the country. Competition rules based on the law will gradually be introduced into the political life of the country.

PROBLEMS OF WESTERNIZATION OF THE CONTEMPORARY RUSSIAN POLITICAL CULTURE

In 1993 Russia announced the westernization of its political system. Its main institutions were enshrined in the Constitution of the Russian Federation (democracy, republic, separation of powers, rule of law). However, the researchers note that the reform failed. Russia only simulates the transition to Western standards of life. The author of the study sets himself the task of identifying the reasons for failure in the nature of the country's political culture. Applying a dialectical and materialistic approach to the problem, the author reveals the influence of the economic system of the country, the social structure of society, imitative changes in the political system, socialization, and traditions of society on the nature of the political culture of Russia. Based on his previous research, the author introduces a number of new explanatory theories. In his opinion, the movement towards the Western model is slowed down by the administrative class which does not want to lose its dominant position. It is not ready to move to a competitive political system, in which it loses its power and turns into a bureaucracy dependent on public politicians representing society. The service intelligentsia is engaged in spreading the public consciousness that is beneficial to the administrative class. Together, they support the type of consciousness of the population that is beneficial to them. Western political ideology is spread in society by the civil intelligentsia, but its significance is not great. The majority of the population agrees with the rule of the administrative class and votes in support of it. Therefore, there is no competitive political system in Russia. The mass consciousness of Russians remains irrational, which allows them to control it with the help of symbolic actions. It retains such archaic features as herd status and infantilism. An infantile person needs a master who decides for him in which direction society will develop, organizes this development, takes care of the population. People express dissatisfaction with this master, but accept his power and obey him. The degree of westernization of Russia's political culture is still very insignificant. The author defines it as 3 points out of 10. The political culture of Russia will be westernized as competitive capitalist relations develop in the country. Competition rules based on the law will gradually be introduced into the political life of the country.

DETECTION OF MARKERS OF LATENT TUBERCULOSIS INFECTION IN ULTRAPASTEURIZED MILK PRODUCED IN DIFFERENT COUNTRIES

The genome of tuberculosis mycobacterium (MTB) was detected in ultrapasteurized milk from countries that have and do not have free status from bovine tuberculosis. Also cell wall deficient (CWD) MTB were isolated from all milk samples, that indicates latent tuberculosis infection in herds supplying milk to dairy enterprises.
 It was found that ultrasmall (less than 0.22 μm) thermally stable protective forms of MTB were present in milk. They can restore viability as CWD MBT and possibly play a role in the induction of oncogenesis and other pathological conditions.
 The existing criteria determining the status of herds do not allow the detection of latent tuberculosis infection, since persistent CWD (L-) forms of MBT do not cause the development of macroscopic changes and hypersensitivity to tuberculin. To identify the real situation in the herds, it is necessary to use PCR and to inoculate special nutrient media with blood and milk mixed with mycobacterial growth stimulants.

Bovine Viral Diarrhea Virus within and herd prevalence on pasture-based dairy systems, in southern Chile dairy farms

Bovine Viral Diarrhea (BVD) is a ubiquitous endemic disease in most bovine populations that causes a negative economic impact on cattle production systems. However, true herd and individual prevalence in Chile have not been estimated based on statistical and epidemiological considerations and uncertainty regarding the infection's extension at animal and herd levels. In addition, the risk factors that can influence how the infection has spread among the cattle premises have not been assessed yet. Therefore, the study aimed to estimate true herd and animal prevalence of active BVDV infection in pasture-based dairy herds and to evaluate risk factors potentially associated with the status of herds and the within-herd prevalence, using a Bayesian approach.A cross-sectional study was performed over a random stratified (proportional to herd size) sample of one-hundred and fifty dairy herds selected in Chile's two leading dairy regions (Region de Los Ríos and Region de Los Lagos). We obtained 12.311 blood samples from lactating cows, but 4.998 randomly selected samples were processed due to budget constraints. For estimating BVDV Herd Prevalence (HP), a herd was considered infected if at least one positive animal to Ag-ELISA was found. In addition, a survey was completed on each farm, aiming to collect information to assess the influence of some variables over the state of the herds; both estimations were obtained using a Bayesian approach.True herd prevalence and true individual prevalence of BVDV active infection were estimated at 77 % and 3.5 % respectively, no significant differences were found between characteristics like herd size, location, vaccination, etc. Open herds and herds that mix herd categories are more likely to have higher BVDV prevalence.

Next Generation of Voluntary PRRS Virus Regional Control Programs.

Porcine reproductive and respiratory syndrome virus (PRRSV) became pandemic in the 1980's and today remains one of the most significant pathogens of the global swine industry. At the herd level, control of PRRSV is complicated by its extreme genetic diversity and its ability to persist in pigs, despite an active immune response. Ultimately, PRRSV control or elimination requires the coordination and active cooperation of producers and veterinarians at the regional level. Early voluntary PRRSV regional control programs focused on routine diagnostic testing and voluntary data-sharing regarding the PRRSV status of participants' herds, but no pre-defined action plans or decision trees were developed to secure project successes (or recover from failures). Given that control of PRRSV is paramount to producer profitability, we propose a coordinated approach for detecting, controlling, and ultimately eliminating wild-type PRRSV from herds participating in regional projects. Fundamental to project success is real-time, multi-platform communication of all data, information, and events that concern the regional project and project participants. New to this approach is the concept of agreed-upon action plans to be implemented by project participants in response to specific events or situations. The simultaneous and coordinated implementation of these strategies allows for early detection of wild-type PRRSV virus introductions and rapid intervention based on agreed-upon response plans. An example is given of a project in progress in the Midwest USA.

Establishing Mycoplasma hyopneumoniae herd status classification criteria for breeding herds

A standardized system for classifying the Mycoplasma hyopneumoniae status of swine breeding herds was developed by defining a set of diagnostic guidelines to determine the exposure and shedding status of herds. The classification is based on epidemiological and ecological features of M hyopneumoniae and reflects current field control and elimination practices. The classification was developed by a working group composed of representatives from academia, industry, swine practitioners, American Association of Swine Veterinarians (AASV), and the National Pork Board, and approved by the AASV Board of Directors on October 2, 2019. Clear and concise terminology will facilitate communication across all stakeholders.

High Prevalence and Factors Associated With the Distribution of the Integron intI1 and intI2 Genes in Scottish Cattle Herds.

Integrons are genetic elements that capture and express antimicrobial resistance genes within arrays, facilitating horizontal spread of multiple drug resistance in a range of bacterial species. The aim of this study was to estimate prevalence for class 1, 2, and 3 integrons in Scottish cattle and examine whether spatial, seasonal or herd management factors influenced integron herd status. We used fecal samples collected from 108 Scottish cattle herds in a national, cross-sectional survey between 2014 and 2015, and screened fecal DNA extracts by multiplex PCR for the integrase genes intI1, intI2, and intI3. Herd-level prevalence was estimated [95% confidence interval (CI)] for intI1 as 76.9% (67.8–84.0%) and intI2 as 82.4% (73.9–88.6%). We did not detect intI3 in any of the herd samples tested. A regional effect was observed for intI1, highest in the North East (OR 11.5, 95% CI: 1.0–130.9, P = 0.05) and South East (OR 8.7, 95% CI: 1.1–20.9, P = 0.04), lowest in the Highlands. A generalized linear mixed model was used to test for potential associations between herd status and cattle management, soil type and regional livestock density variables. Within the final multivariable model, factors associated with herd positivity for intI1 included spring season of the year (OR 6.3, 95% CI: 1.1–36.4, P = 0.04) and watering cattle from a natural spring source (OR 4.4, 95% CI: 1.3–14.8, P = 0.017), and cattle being housed at the time of sampling for intI2 (OR 75.0, 95% CI: 10.4–540.5, P < 0.001). This study provides baseline estimates for integron prevalence in Scottish cattle and identifies factors that may be associated with carriage that warrant future investigation.

Bayesian accuracy estimates of environmental sampling for determining herd paratuberculosis infection status and its association with the within-herd individual fecal culture prevalence in Québec dairies

The objectives of this retrospective analysis were to: 1) estimate the diagnostic sensitivity (Se) and specificity (Sp) of bacterial culture of environmental samples for determining Mycobacterium avium subsp. paratuberculosis (MAP) infection status in Québec dairies, using a Bayesian Latent Class Model (BLCM); and 2) determine the association between the number of positive environmental samples and the individual fecal culture (IFC) apparent and true MAP within-herd prevalence.Environmental and individual fecal samples were collected from 87 commercial dairy herds participating in previous research projects. Environmental samples included two composite samples of 20 g collected from different locations within each of the following sites: an area where manure from the majority of adult cattle accumulates, a manure storage area and another site of manure accumulation chosen by the veterinarian. Samples were cultured using the MGIT Para TB culture liquid media and the BACTEC MGIT 960 system. The Se and Sp of environmental sampling were estimated using a one-test-one-population BLCM. Herds were considered positive for environmental sampling if at least one out of the six samples collected was positive. The apparent and true IFC within-herd MAP prevalence estimates for each herd were obtained using a two-stage cluster BLCM, then merged in a single dataset with the environmental sample results. The association between the within-herd MAP prevalence results (apparent and true), and the number of positive environmental samples was assessed using a zero-inflated negative binomial (ZINB) model. In all BLCMs, median posterior estimates and 95 % Bayesian credible intervals (BCI) were obtained with OpenBUGS statistical freeware.Se and Sp of environmental sampling were 43.7 % (95 % BCI: 32.5−55.5) and 96.2 % (95 % BCI: 84.2−99.8), respectively. Overall, the number of positive environmental samples increased with the apparent and true MAP within-herd prevalence. The true prevalence was higher than the apparent prevalence for a given number of positive environmental samples. The probability of not observing a positive environmental sample decreased with the prevalence.Despite its imperfect accuracy, environmental sampling is an inexpensive and non-invasive sampling method to determine MAP infection status in tie-stall herds that can be used as a proxy to estimate the true within-herd prevalence. The absence of positive environmental samples in a single sampling visit is likely an indicator of a very low within-herd prevalence rather than being MAP exempt.

Evaluation of risk-based surveillance strategies for Salmonella Dublin in Danish dairy herds by modelling temporal test performance and herd status classification errors

The potential risk-based improvement of the Salmonella Dublin surveillance programme in Danish dairy herds was investigated, considering herd status misclassifications due to testing errors. The programme started in October 2002. Currently (early 2021) all dairy herds are classified based on quarterly bulk tank milk (BTM) testing with an indirect antibody ELISA (iELISA). Over the last two decades, the prevalence of herds classified as “likely infected” (levels 2,3) reduced remarkably. However, since 2015, the apparent prevalence has increased again, calling for improved surveillance and control to protect animal and human health. A deterministic simulation model based on data (2018–2019) from 2283 dairy herds in level 1 (“most likely free from infection”), was developed to estimate status misclassifications as false negative (FN) and false positive (FP) herds, under two testing strategies. These were: (A) the current system based on quarterly BTM testing only, and (B) an alternative strategy based on additional blood testing of up to eight calves, within herds at high risk of infection (HR). Both strategies were evaluated using three risk classification methods (I to III) and four sensitivity analysis scenarios (SA1-4), where different temporal performances were simulated for the iELISA in BTM. To apply strategy B, the best high-risk classification method (II), which combined managerial applicability and minimized errors, would require testing approximately 1000 calves across 127 HR herds. In that case, strategy A would cause 3 FNs and 67 FPs, by assuming annual BTM sensitivity (BTMSe) 95% conditional on a 1-year disease history and specificity (BTMSp) 97%. Whereas strategy B could cause a similar number of FNs, but 7 FPs more, assuming a sensitivity (Se) of 77% and specificity (Sp) of 99% in individual blood-samples (SA1). Assuming also quarterly BTMSe 53% and BTMSp 99.9% (SA4), strategy A derived 28 FNs and 2 FPs, while strategy B resulted in 6 FNs less and 8 FPs more. Therefore, strategy B could improve early detection of infected HR herds, while strategy A would avoid more unnecessary restrictions in false-positive herds. This improves knowledge on the potential use of additional blood testing in HR herds and illustrates how deterministic modelling can be used to improve disease surveillance and control.

Identification of different attitudes towards paratuberculosis control using cluster analysis applied on data from an anonymous survey among German cattle farmers

BackgroundParatuberculosis is a common disease in ruminants, causing economic losses in livestock farming, and a relationship between the exposure to its causative agent Mycobacterium avium subsp. paratuberculosis, and Crohn’s disease in humans is discussed. Despite this, only a minority of cattle farmers have enroled in voluntary control programmes in most countries. Therefore, this study aimed at investigating the farmer’s opinion on paratuberculosis and their motivations to participate in a control programme. The objective was to identify different groups among farmers regarding their motivation and thereby contribute to a better understanding of farmers’ attitudes towards paratuberculosis control.ResultsTwo hundred twenty-five farmers responded to questionnaires that were distributed among cattle farmers in Saxony and Thuringia, federal states of Germany, together with boot-swab sampling sets for a free and anonymous herd-level paratuberculosis test. Among them, dairy herds and large herds were overrepresented. A hierarchical cluster analysis of the farmers’ answers resulted in four groups that we tagged as ‘informed sceptics’, ‘deniers’, ‘affected supporters’ and ‘free supporters’. In all groups, the majority considered paratuberculosis a threat to the public image of cattle farmers. Nearly all participants wanted to know the paratuberculosis herd status of purchased cattle. In contrast to the supporters, the informed sceptics and the deniers did not consider paratuberculosis a dangerous epizootic disease and would not welcome a mandatory control programme. The deniers and the affected supporters, but not the informed sceptics and the free supporters, assumed that their herd is affected by paratuberculosis. Unlike the deniers, all other groups would enrol in a control programme if the pathogen would have been found in their herd. Protecting future profitability and improving animal health were the two most important motivations to control paratuberculosis in all groups followed by aspects related to the marketing of breeding cattle. Most frequently, the costs and the assumed inaccuracy of diagnostics tests were mentioned as obstacles that hamper programme enrolment.ConclusionsSignificantly different attitudes of farmers regarding paratuberculosis control were identified. Therefore, tailored rather than uniform communication strategies are required to enhance participation in voluntary paratuberculosis control programmes.

Proposed modifications to porcine reproductive and respiratory syndrome virus herd classification

A standardized system for classifying the porcine reproductive and respiratory syndrome virus (PRRSV) status of swine herds is necessary for communication between veterinarians and producers. The 2011 classification system has been widely adopted by producers and veterinarians worldwide. In 2018, a working group met to revisit the system and make recommendations for changes. The most significant modification was to the classification of positive unstable and positive stable breeding herds. Recommended diagnostic protocols for promotion of herds to each status were modified and recommended diagnostic protocols to maintain a status were added. The growing pig classification for PRRSV was also modified.

Control and Eradication Programs for Six Cattle Diseases in the Netherlands.

Within the European Union, infectious cattle diseases are categorized in the Animal Health Law. No strict EU regulations exist for control, evidence of disease freedom, and surveillance of diseases listed other than categories A and B. Consequently, EU member states follow their own varying strategies for disease control. The aim of this study was to provide an overview of the control and eradication programs (CPs) for six cattle diseases in the Netherlands between 2009 and 2019 and to highlight characteristics specific to the Dutch situation. All of these diseases were listed as C,D or E in the New Animal Health Law. In the Netherlands, CPs are in place for six endemic cattle diseases: bovine viral diarrhea, infectious bovine rhinotracheitis, salmonellosis, paratuberculosis, leptospirosis, and neosporosis. These CPs have been tailored to the specific situation in the Netherlands: a country with a high cattle density, a high rate of animal movements, a strong dependence on export of dairy products, and a high-quality data-infrastructure. The latter specifically applies to the dairy sector, which is the leading cattle sector in the Netherlands. When a herd enters a CP, generally the within-herd prevalence of infection is estimated in an initial assessment. The outcome creates awareness of the infection status of a herd and also provides an indication of the costs and time to achieve the preferred herd status. Subsequently, the herd enrolls in the control phase of the CP to, if present, eliminate the infection from a herd and a surveillance phase to substantiate the free or low prevalence status over time. The high-quality data infrastructure that results in complete and centrally registered census data on cattle movements provides the opportunity to design CPs while minimizing administrative efforts for the farmer. In the CPs, mostly routinely collected samples are used for surveillance. Where possible, requests for proof of the herd status are sent automatically. Automated detection of risk factors for introduction of new animals originating from a herd without the preferred herd status i.e., free or unsuspected, is in place using centrally registered data. The presented overview may inspire countries that want to develop cost-effective CPs for endemic diseases that are not (yet) regulated at EU level.

Predicting sensitivity of repeated environmental sampling for Mycobacterium avium subsp. paratuberculosis in dairy herds using a Bayesian latent class model

Between-herd transmission of Mycobacterium avium subsp. paratuberculosis (MAP) by subclinically infected cattle is an important risk which can hamper effective control of paratuberculosis. Knowledge of herd status would substantially reduce this risk; MAP positive farms can be detected with environmental sampling. The objective of this study was to compare cumulative sensitivities of annual environmental sampling with two or four samples per sampling event without knowledge of true herd status and to calculate the number of sampling events to achieve a cumulative sensitivity of at least 0.9. Data from three repeated sampling events in two study populations, one with 55 herds (two samples/event) and another with 30 herds (four samples/event) including test results, herd and sample characteristics and prior prevalence estimates, were derived from the Alberta Johne’s Disease Initiative (Alberta, Canada). A recursive Bayesian latent class model was used to predict the cumulative sensitivity of repeated environmental sampling events. A sampling scheme with four samples per sampling event had a higher cumulative sensitivity than an alternative scheme with two samples.To achieve a cumulative sensitivity of at least 0.9 with 95% probability, eight sampling events with two environmental samples per set, or four sampling events with four samples per set were required. Further model assessment demonstrated that these results can only be generalized to cattle populations with a similar within-herd prevalence to those studied here (approximately 0.08). Nonetheless, these results could help predict herd-level prevalence in cattle populations after environmental testing and provide information regarding the uncertainty behind status estimates for herds repeatedly tested using environmental samples.

Comparing surveillance approaches to support regaining free status after a foot-and-mouth disease outbreak

Following an FMD eradication program, surveillance will be required to demonstrate that the program has been successful. The World Organization for Animal Health (OIE) provides guidelines including waiting periods and appropriate surveillance to support regaining FMD-free status. Serological surveillance is the recommended method for demonstrating freedom but is time consuming and expensive. New technologies such as real-time reverse transcription polymerase chain reaction (RT-qPCR) tests and sampling techniques such as bulk milk testing (BMT) of dairy cattle, oral swabs, and saliva collection with rope tethers in piggeries could enable surveillance to be done more efficiently. Epidemiological modelling was used to simulate FMD outbreaks, with and without emergency vaccination as part of the response, in Australia. Baseline post-outbreak surveillance approaches for unvaccinated and vaccinated animals based on the European FMD directive were compared with alternative approaches in which the sampling regime, sampling approaches and/or the diagnostic tests used were varied. The approaches were compared in terms of the resources required, time taken, cost, and effectiveness i.e., ability of the surveillance regime to correctly identify the infection status of herds. In the non-vaccination scenarios, the alternative approach took less time to complete and cost less, with the greatest benefits seen with larger outbreaks. In vaccinated populations, the alternative surveillance approaches significantly reduced the number of herds sampled, the total number of tests done and costs of the post-outbreak surveillance. There was no reduction in effectiveness using the alternative approaches, with one of the benefits being a reduction in the number of false positive herds. Alternative approaches to FMD surveillance based on non-invasive sampling methods and RT-qPCR tests have the potential to enable post outbreak surveillance substantiating FMD freedom to be done more quickly and less expensively than traditional approaches based on serological surveys.

Developing a Reference Framework for Typical Development in the Young Pig

Abstract Objectives The majority of infants in the US do not receive exclusive breastfeeding in the first six months of age, highlighting the necessity of infant formula. The artificially reared piglet is a common model utilized to support substantiation of novel bioactive components in milk or infant formula. However, it is currently unclear to what extent maternal and environmental rearing confounders affect growth outcomes in early life nutrition piglet studies. The objective of the present work is to use historical data to begin to chart typical development of the pig and to develop healthy reference value ranges for the purpose of assessing the safety of bioactive components in infant formula. Methods 8 piglet studies conducted at the University of Illinois Urbana-Champaign over the past ten years were compiled to create and model reference values for body and organ weights in artificially-reared and sow reared pigs. Metadata were organized to include milk replacer sources, bioactive components, sex, breed, source of herd, feeding rates, rearing styles, and health status. A combination of statistical models including simple linear regression, polynomial regression, and generalized additive models were used to analyze how such parameters influence typical growth. The diet of the 18 studies were blinded during data modeling phase. Results Over 13,000 data points from over 500 animals were identified to be suitable for data mining. Minimal differences in the growth of artificially or sow reared pigs were observed in the first 30 days of life (P &amp;gt; 0.05). Similarly, male and female bodyweight growth were nearly identical (P &amp;gt; 0.05). Development outcomes such as brain, liver, and intestinal organ weights were classified as typical for developing pigs. A subset of the data containing subjects with poor growth was identified to model growth under deficient or sub-optimal conditions. Conclusions The use of artificial rearing had no impact on body weight, nor did sex contribute to differences in growth during early life. Ultimately, these data can be used to create preliminary weight-for-age charts in the pig model to better interpret whether bioactive ingredients tested in the pig model affect animal growth within typical reference values. Funding Sources Funding was provided by Mead Johnson Nutrition, LLC, a Reckitt Benckiser LLC company.