Pigs in southern Italy are exposed to three ruminant pathogens: an analysis of seroprevalence and risk factors analysis study.

BACKGROUND: Pigs are susceptible to several ruminant pathogens, including Coxiella burnetti, Schmallenberg virus (SBV) and bovine viral diarrhea virus (BVDV). These pathogens have already been described in the pig population, although the dynamics of the infection and the impact on pig farms are currently unclear. The aim of this work was to evaluate the presence of these infections in the pig population of the Campania region, southern Italy, and to evaluate the risk factors associated with a greater risk of exposure. RESULTS: A total of 414 serum samples belonging to 32 herds were tested for the presence of antibodies against SBV, Coxiella, and BVD using commercial multispecies ELISA kits. SBV (5.3%) was the most prevalent pathogen, followed by Coxiella (4.1%) and BVD (3%). The risk factors included in the study (age, sex, province, farming system, ruminant density and major ruminant species) had no influence on the probability of being exposed to BVD and Coxiella, except for the location, in fact more pigs seropositive to Coxiella were found in the province of Caserta. However, the univariate analysis highlighted the influence of age, location, and sex on exposure to SBV. The subsequent multivariate analysis statistically confirmed the importance of these factors. The presence of neutralizing antibodies for SBV and BVDV, or antibodies directed towards a specific phase of infection for Coxiella was further confirmed with virus-neutralization assays and phase-specific ELISAs in a large proportion of positive samples. The presence of high neutralizing antibody titers (especially for SBV) could indicate recent exposures. Twelve of the 17 positive samples tested positive for antibodies against Coxiella phase I or II antigens, indicating the presence of both acute and chronic infections (one animal tested positive for both phases antibodies). CONCLUSIONS: Our study indicates a non-negligible exposure of pigs from southern Italy to the above pathogens. Further studies are necessary to fully understand the dynamics of these infections in pigs, the impact on productivity, and the public health consequences in the case of Coxiella.

Outbreak of persistently infected heifer calves with bovine viral diarrhea virus subgenotypes 1b and 1d in a BVDV-vaccinated open dairy herd.

Bovine viral diarrhea virus (BVDV) infection has a significant economic impact on beef and dairy industries worldwide. Fetal infection with a non-cytopathic strain may lead to the birth of persistently infected (PI) offspring, which is the main event in the epidemiological chain of BVDV infection. This report describes the birth of 99 BVDV-PI heifer calves within 52 days of birth in a regular BVDV-vaccinated Brazilian dairy cattle herd and the subgenotypes of the infecting field strains. This study was conducted in a high-yielding open dairy cattle herd that frequently acquired heifers from neighboring areas for replacement. The farm monitors the birth of PI calves by screening all calves born using an ELISA (IDEXX) for BVDV antigen detection. All calves aged 1-7 days were evaluated. For positive and suspected results, the ELISA was repeated when the calves were close to one month old. A total of 294 heifer calves were evaluated between February and March 2021. Of these, 99 (33.7 %) had positive ELISA results and were considered PI calves. To evaluate the predominant BVDV species and subgenotypes in this outbreak, whole blood samples were collected from 31 calves born during the study period. All samples were submitted to the RT-PCR assay for the partial amplification of the BVDV 5'-UTR region, and these amplicons were subjected to nucleotide sequencing. Phylogenetic analysis identified BVDV-1b and BVDV-1d in 16 and 13 heifer calves, respectively. In two calves, it was not possible to determine the BVDV-1 subgenotype. Detection of PI animals and monitoring of circulating BVDV subgenotype strains are central to disease control. This study shows that regular BVDV vaccination alone may be insufficient to prevent BVDV infection in high-yielding open dairy cattle herds. Other biosecurity measures must be adopted to avoid the purchase of cattle with acute infections by BVDV or BVDV-PI, which can cause a break in the health profile of the herd and economic losses.

Bovine viral diarrhoea viruses from New Zealand belong predominantly to the BVDV-1a genotype.

AIM: To determine which genotypes of bovine viral diarrhoea virus (BVDV) circulate among cattle in New Zealand. METHODS: Samples comprised BVDV-1-positive sera sourced from submissions to veterinary diagnostic laboratories in 2019 (n = 25), 2020 (n = 59) and 2022 (n = 74) from both beef and dairy herds, as well as archival BVDV-1 isolates (n = 5). Fragments of the 5' untranslated region (5' UTR) and glycoprotein E2 coding sequence of the BVDV genome were amplified and sequenced. The sequences were aligned to each other and to international BVDV-1 sequences to determine their similarities and phylogenetic relationships. The 5' UTR sequences were also used to create genetic haplotype networks to determine if they were correlated with selected traits (location, type of farm, and year of collection). RESULTS: The 5' UTR sequences from New Zealand BVDV were closely related to each other, with pairwise identities between 89% and 100%. All clustered together and were designated as BVDV-1a (n = 144) or BVDV-1c (n = 5). There was no evidence of a correlation between the 5' UTR sequence and the geographical origin within the country, year of collection or the type of farm. Partial E2 sequences from New Zealand BVDV (n = 76) showed 74-100% identity to each other and clustered in two main groups. The subtype assignment based on the E2 sequence was the same as based on the 5' UTR analysis. This is the first comprehensive analysis of genomic variability of contemporary New Zealand BVDV based on the analysis of the non-coding (5' UTR) and coding (E2) sequences. CONCLUSIONS AND CLINICAL RELEVANCE: Knowledge of the diversity of the viruses circulating in the country is a prerequisite for the development of effective control strategies, including a selection of suitable vaccines. The data presented suggest that New Zealand BVDV are relatively homogeneous, which should facilitate eradication efforts including selection or development of the most suitable vaccines.

Uncommon bovine viral diarrhea virus subtype 1e associated with abortions in cattle in southern Brazil.

We characterized bovine viral diarrhea virus (BVDV)-related abortions in cattle and identified the species and subgenotypes in the state of Santa Catarina, southern Brazil. Our RT-PCR assay was positive for BVDV in 5 fetuses from different farms; however, 3 of the 5 fetuses were also PCR-positive for Neospora caninum. In the 5 BVDV-positive fetuses, gross lesions included fetal mummification (1), hepatomegaly (1), subcutaneous edema (1), and perirenal edema (1). Predominant histologic lesions included epicarditis and mild-to-moderate lymphoplasmacytic myocarditis (5), mild multifocal lymphoplasmacytic interlobular pneumonia (4), nephrosis associated with moderate multifocal interstitial nephritis (1), moderate multifocal lymphoplasmacytic necrotic hepatitis (1), and mild multifocal lymphoplasmacytic meningitis (1). The amplification products from the Pestivirus 5'UTR region of 4 of the 5 fetuses had 96.3-100% similarity between fetal strains and reference strains. The samples were distributed into 2 branches of the phylogenetic tree; strains UDESC:01, UDESC:02, and UDESC:05 clustered in the BVDV-1e branch, uncommon in the Americas, and strain UDESC:04 clustered in the BVDV-2b branch. The three 1e strains had 96.9-97.4% similarity.

Sporadic bovine encephalopathy caused by Chlamydia pecorum secondary to bovine viral diarrhoea virus infection in calves in South Australia.

BACKGROUND: Despite bovine viral diarrhoea virus and Chlamydia pecorum being important endemic diseases of cattle, there are limited reports of theirco-occurrence. CASE REPORT: Several 12-18-week-old, weaned Hereford calves presented with ill-thriftiness and neurological signs on a mixed cattle and sheep farm in South Australia in July 2021. Immune suppression resulting from transient infection with bovine viral diarrhoea virus (BVDV) is implicated in predisposing to infection with Chlamydia pecorum, the causative agent of sporadic bovine encephalopathy (SBE). Chlamydia spp. are difficult to culture in vitro or definitively identify based on current standard molecular based tests. In this case, diagnosis was confirmed by immunohistochemistry. CONCLUSION: To the authors' knowledge, this case report is the first to document BVDV transient infection occurring in conjunction with SBE. Given the current high prevalence of BVDV on Australian farms, such co-infections may have significant future clinical relevance. This case also highlights the need for appropriate tests, such as immunohistochemistry to demonstrate the causative organism in histological lesions and thus reduce the occurrence of false negative diagnosis.

Seroprevalence of five diarrhea-related pathogens in bovine herds of scattered households in Inner Mongolia, China between 2019 and 2022.

Bovine diarrhea is a multi-factorial disease and remains one of the biggest health problems in animal husbandry. The endemic trends of the main pathogens responsible for bovine diarrhea in Inner Mongolia have not been analyzed systematically before. Therefore, the purpose of this study was to estimate the prevalence of bovine diarrhea pathogens found in the scattered households of Inner Mongolia in China. Additionally, we assessed for differences in the prevalence of infection based on age and region, as well as determined local prevalence rates and the rates of mixed infections. Using a two-stage random sampling strategy, 3,050 serum samples were collected from 72 bovine herds in 11 leagues and cities in Inner Mongolia, and the positive rates of BVDV, BRV, BCoV, K99, and Mycobacterium paratuberculosis (M. paratuberculosis) antibodies in the samples were detected by ELISA to determine the epidemic trends and epidemic differences of the five pathogens in Inner Mongolia. The positive rates of antibodies based on serum samples were: BVDV, 18.79% (95% CI [17.44-20.22]); BRV, 12.39% (95% CI [11.27-13.61]); BCoV, 12.82% (95% CI [11.68-14.05]); K99, 13.80% (95% CI [12.62-15.07]); and M. paratuberculosis, 10.79% (95% CI [9.74-11.94]). The prevalence rates of BRV, BCoV and K99 at 0-2 months were significantly different from that at 2-6 months, 6-18 months and adult cattle (P < 0.05). The prevalence of BVDV and M. paratuberculosis was the highest in adult cattle, which was significantly different from that in other age groups (P < 0.05). Furthermore, obvious regional epidemiological differences among the five diseases were observed. There was a mixed infection of BRV+BCoV in each age stage, the highest mixed infection being BVDV+BRV+K99 at 0-2 months of age. Our results showed that the cattle of scattered households in the Inner Mongolia of China were endemicly infected with several important cattle pathogens. Most of the pathogens studied occurred between 0-2 months of age and were mixed infections, which greatly influences the health of the cattle and leads to economic loss. These findings are of practical significance for the future prevention and control of bovine diarrhea in the Inner Mongolia or other regions of China.

Assessing the reliability of innovative criteria to certify that cattle are non-Persistently Infected (non-PI) with the Bovine Viral Diarrhoea Virus (BVDV).

Persistently Infected (PI) animals play a central role in the transmission of BVDV infection between cattle herds. Thus, promoting the certification of non-PI animals is a relevant approach for improving control, as it contributes to securing the trade. The objectives of this study were: i) to assess the reliability of diverse certification criteria, and ii) to identify risk factors for erroneous certification. To do so, the proportion of animals wrongly certified as non-PI on the basis of tests performed after the certification date, was calculated for each criterion. The data used were collected in herds located in Brittany, involved in either a clearance process for those that were infected, or in a surveillance process for herds that were BVDV-free. A total of 23 criteria were defined by combining the technical characteristics of the tests (individual vs. pool; single vs. repeated; direct vs. indirect tests), and some pathogenic characteristics of BVDV infection. Overall, the rates of wrongly-certified animals were low (mean: 1.3 10-4). Direct and indirect criteria had equivalent performances. Heifers from birth, and even foetuses in the last third of gestation, are certified, provided that the herd to which they belong has been free of BVDV for more than 2.5 years. The risk for wrong certification increased in the case of PIs present in the herd or its surroundings. The simplicity of the output-based approach described here, and the excellent performance of indirect criteria relying on serological monitoring of BTM, make it particularly interesting, as its use could facilitate trade between countries.

Molecular and serological survey of bovine viral diarrhea virus infection in cattle in Kazakhstan.

The aim of this study was to estimate the occurrence of bovine viral diarrhea virus (BVDV) infection and to assess the population immunity in cattle vaccinated against BVDV in different regions of Kazakhstan. Cattle samples were collected in 12 oblasts (43 districts) of Kazakhstan. A total of 2477 cattle from 114 herds and 21 Bukhara deer (Cervus elaphus bactrianus) were examined by ELISA and conventional RT-PCR. Univariate and multivariate logistic regression analysis was performed to identify risk factors associated with BVDV infection in the country. In total, antibodies against BVDV were found in 79.3% (1965/2477) of all the animals and 92.1% (105/114) of all the herds examined. Seroprevalence in unvaccinated and vaccinated animals was 48.6% (447/920) and 98.7% (1391/1410), respectively. Seroprevalence in deer was 19.1% (4/21). The BVDV RNA was detected in six unvaccinated cattle (0.2%). Sequence analysis of the 5'-untranslated region demonstrated that four of the detected strains belonged to BVDV-1 and two strains to BVDV-2. Regression analysis revealed that age, production type, housing method, farm size, and geographic location were risk factors for BVDV infection in cattle in Kazakhstan. The present data confirm circulation of BVDV-1 and BVDV-2 in Kazakhstan and highlight the need to improve strategies for prevention and control of BVDV infection in the country.

A framework for assessing confidence in freedom from infection in animal disease control programmes.

In the Surveillance Tool for Outcome-based Comparison of FREEdom from infection (STOC free) project (https://www.stocfree.eu), a data collection tool was constructed to facilitate standardised collection of input data, and a model was developed to allow a standardised and harmonised comparison of the outputs of different control programmes (CPs) for cattle diseases. The STOC free model can be used to evaluate the probability of freedom from infection for herds in CPs and to determine whether these CPs comply with the European Union's pre-defined output-based standards. Bovine viral diarrhoea virus (BVDV) was chosen as the case disease for this project because of the diversity in CPs in the six participating countries. Detailed BVDV CP and risk factor information was collected using the data collection tool. For inclusion of the data in the STOC free model, key aspects and default values were quantified. A Bayesian hidden Markov model was deemed appropriate, and a model was developed for BVDV CPs. The model was tested and validated using real BVDV CP data from partner countries, and corresponding computer code was made publicly available. The STOC free model focuses on herd-level data, although that animal-level data can be included after aggregation to herd level. The STOC free model is applicable to diseases that are endemic, given that it needs the presence of some infection to estimate parameters and enable convergence. In countries where infection-free status has been achieved, a scenario tree model could be a better suited tool. Further work is recommended to generalise the STOC free model to other diseases.

Dans le cadre du projet européen STOC free (Surveillance Tool for Outcome-based Comparison of FREEdom from infection, outil de surveillance permettant de comparer les probabilités d'absence d'infection sur la base des résultats, https://www.stocfree.eu), un outil de recueil des données a été construit pour faciliter une collecte normalisée des données d'entrée ; un modèle a également été élaboré pour permettre une comparaison normalisée et harmonisée des données sur les résultats des différents programmes de contrôle des maladies des bovins. Le modèle STOC free peut être utilisé pour évaluer la probabilité d'absence d'infection au sein des troupeaux dans le cadre des programmes de contrôle et déterminer si ces programmes sont conformes aux normes définies par l'Union européenne en termes de résultats attendus. L'infection par le virus de la diarrhée virale bovine a été choisie comme maladie d'étude pour ce projet en raison de la diversité des programmes de contrôle dans les six pays participants. Les informations relatives aux programmes de contrôle et aux facteurs de risque d'infection ont été recueillies à l'aide de l'outil de collecte des données. Les aspects clés et valeurs par défaut ont été quantifiés en vue d'être inclus dans le modèle STOC free. Un modèle de Markov caché dont les paramètres sont estimés par inférence bayésienne a été considéré comme le plus adapté et développé pour une application aux données issues des programmes de contrôle de la diarrhée virale bovine. Ce modèle a été testé et validé en utilisant des données réelles des programmes de contrôle du virus de la diarrhée virale bovine des pays participants ; le code informatique correspondant a été rendu public. Le modèle STOC free utilise des données au niveau des troupeaux, même si des données au niveau des animaux individuels peuvent être incluses une fois agrégées au niveau du troupeau. Le modèle STOC free s'applique aux maladies endémiques, puisqu'un certain niveau de présence de l'infection est nécessaire pour estimer les paramètres et permettre la convergence. Dans les pays ayant obtenu le statut indemne d'infection, un modèle du type arbre de scénario pourrait être un outil plus adapté. Des travaux supplémentaires sont recommandés pour généraliser le modèle STOC free à d'autres maladies.

Como parte del proyecto europeo STOC free (Surveillance Tool for Outcome-based Comparison of FREEdom from infection, herramienta de vigilancia para comparaciones por resultados respecto a la ausencia de infecciones, https://www.stocfree.eu), se confeccionó una herramienta de obtención de datos para facilitar la recogida normalizada de datos entrantes y se elaboró un modelo que posibilitara una comparación normalizada y armonizada de los resultados (datos salientes) de distintos programas de control de enfermedades bovinas. El modelo STOC free puede servir para calcular la probabilidad de ausencia de infección en los rebaños como parte de los programas de control y para determinar si estos programas se ajustan a las normas predefinidas de resultados de la Unión Europea. Como ejemplo de estudio para el proyecto se eligió el virus de la diarrea viral bovina (virus DVB) por la diversidad que presentaban los correspondientes programas de control de los seis países participantes. Empleando la herramienta de obtención de datos, se reunió información pormenorizada de los programas de control del virus DVB y los factores de riesgo. Para incluir los datos en el modelo STOC free, se cifraron unos aspectos clave y valores predeterminados Juzgando conveniente el empleo de un modelo oculto de Markov cuyos parámetros se estiman por inferencia bayesiana, se elaboró un modelo de esta índole aplicable a los programas de control del virus DVB. Para ensayar y validar el modelo se utilizaron datos reales de los programas de control del virus DVB de los países participantes, tras lo cual se hizo público el correspondiente código informático. El modelo STOC free trabaja con los datos por rebaño, aunque tras la agregación por rebaños pueden incluirse también datos por individuo. Para que este modelo sea aplicable a una enfermedad es preciso que esta sea endémica, pues el modelo requiere la presencia de cierto nivel de infección para calcular los parámetros y determinar convergencias. En aquellos países donde ya esté reconocida la ausencia de infección, sería más apropiado utilizar como herramienta un modelo de árbol de hipótesis. Los autores recomiendan ahondar en esta línea de trabajo para poder extender a otras enfermedades el uso del modelo STOC free.

The right strategy for you: Using the preferences of beef farmers to guide biosecurity recommendations for on-farm management of endemic disease.

Effective on-farm biosecurity measures are crucial to the post-border protection of emerging agricultural diseases and are the foundation of endemic disease control. Implementation of on-farm biosecurity measures are contingent on the priorities of individual producers, which can often be neglected for other aspects of the farming enterprise. The on-farm approach to prevention of endemic diseases, like bovine viral diarrhoea virus (BVDV), is inconsistent between farms and it is not realistic to assume that farmers take an entirely normative approach to on-farm decision making. Multi-criteria decision analysis (MCDA) has been used for disease prioritisation and national disease control in human and animal health; however, it is yet to be used as a decision tool for disease control at the farm level. This study used MCDA to determine the most appropriate biosecurity combinations for management of BVDV, based on the preferences of Australian beef producers. Beef producer preferences were obtained from an online survey using indirect collection methods. Point of truth calibration was used to aggregate producer preferences and the performance scores of 23 biosecurity combinations for control of BVDV based on four main criteria: the probability of BVDV introduction, the on-farm impact of BVDV, the off-farm impact of BVDV and the annual input cost of the practice. The MCDA found that biosecurity combinations that included "double-fencing farm boundaries" used in conjunction with "vaccination against BVDV" were most appropriate for management of BVDV in an initially naïve, self-replacing seasonal single-calving beef herd over a 15-year period. Beef producers prioritised practices that preserved the on-farm health of their cattle more than any other criteria, a finding that was persistent regardless of demographic or farming type. Consequently, combinations with "vaccination against BVDV" were consistently ranked higher than those that included "strategic exposure of a persistently infected cow," which is sometimes used by Australian beef producers instead of vaccination. Findings of this study indicate that the benefits of "double-fencing farm boundaries" and "vaccination against BVDV" outweigh the relatively high cost associated with these practices based on the priorities of the Australian beef producer and may be used to demonstrate the benefits of on-farm biosecurity during discussions between livestock veterinarians and beef farmers.

First detection of emerging HoBi-like Pestivirus (BVD-3) among some persistently infected dairy cattle herds in Egypt.

Bovine viral diarrhoea virus (BVDV) is a serious veterinary health concern worldwide. We conducted this study to determine the prevalence of persistent infections (PI) and identify the current strain among some dairy cattle herds in Egypt. A total of 240 serum samples were collected from six Egyptian provinces. Between 2019 and 2020, samples were tested by Enzyme linked immunosorbent assay (ELISA) for detection of PI animals, and then molecular characterization was performed. Six calves were found PI with a prevalence of 2.5% (6/240). Using molecular characterization, HoBi-like Pestivirus (BVD-3) was successfully identified in Egypt for the first time. Based on the BVD-3 reference strains on Genbank, the detected strains had an identity ranging from 98.8 to 99.6%. Partial nucleotide sequence of the 5'UTR gene for six tested samples was submitted to Genbank with accessions: OM324396, OM324397, OM324398, OM324399, OM3243100, and OM3243101.

One size does not fit all: Exploring the economic and non-economic outcomes of on-farm biosecurity for bovine viral diarrhoea virus in Australian beef production.

Bovine viral diarrhoea virus (BVDV) is a disease of global importance, affecting the production and welfare of cattle enterprises through poor reproductive performance and calf mortality. In Australia, the prevention of BVDV introduction and spread is primarily achieved with on-farm biosecurity; however, the use of these practices can vary amongst producers. Economic utility is commonly identified as a contributor to the uptake of on-farm biosecurity, but other factors such as animal welfare, producer priorities and introduction risk also influence farmer behaviour. This study uses an individual-based, stochastic simulation model to examine the economic and non-economic value of 23 on-farm biosecurity combinations for the control of BVDV in Australian beef farms without (N0) and with (N1) a neighbouring population of persistently infected (PI) cattle. Combinations of quarantine of purchased bulls (Q), hygiene during herd health events (H), double-fencing adjacent boundaries with neighbouring farms (F) and vaccination against BVDV (V) were tested. This study is the first to simulate the use of strategic PI exposure (PI) as an alternative to V, a contentious practice performed by some Australian beef farmers. Introduction of BVDV into a naïve 300-breeder self-replacing beef herd was achieved through the purchase of PI bulls (N0 and N1 herds) and over-the-fence contact with neighbouring PI animals (N1 herds only). The predicted median cumulative loss due to BVDV over a 15-year period was AUD$172/breeder and AUD$453/breeder for an N0 and N1 herd, respectively. Early establishment of BVDV in the simulation period was found to be the primary factor contributing to economic loss. Consequently, the Q and QF combinations resulted in the highest predicted average annual cost-benefit for BVDV-free N0 and N1 herds. In the five years following establishment of BVDV, use of QP (N0 herds) and V (N1 herds) combinations were most cost-effective. Combinations that involved V and P (in conjunction with F in N1 herds) also resulted in the lowest number of PI animals sold to other farms or feedlots over the simulation period. However, in both N0 and N1 herds, P resulted in the highest number of infected cattle, which has implications for poor animal welfare and increased antimicrobial use on Australian beef farms. The outcomes reported in this study can guide decisions to prevent BVDV introduction and spread on extensive beef farms using on-farm biosecurity, based on the risk of BVDV exposure and the priorities of the individual farmer.

Descriptive analysis of national bovine viral diarrhoea test data in England (2016-2020).

BACKGROUND: Bovine viral diarrhoea virus (BVDV) causes substantial economic losses to the cattle industry; however, control and eradication can be achieved by identifying and removing persistently infected cattle from the herd. Each UK nation has separate control programmes. The English scheme, BVDFree, started in 2016 and is voluntary. METHODS: We analysed the test results submitted to BVDFree from 5847 herds between 2016 and 2020. RESULTS: In 2020, 13.5% of beef breeders and 20.0% of dairy herds that submitted tests had at least one positive (virus/antibody) test result. Although lower than in previous years, there was no clear trend in the proportion of positive tests over time. In virus testing herds, 0.4% of individual tests were positive in 2020, and 1.5% of individual tests were positive in BVDV-positive virus testing herds. Dairy herds and larger herds were more likely to join BVDFree, and dairy herds were also more likely to virus test than beef breeder herds. Larger herds, herds that used virus testing and herds that had BVDV-positive test results were more likely to continue submitting tests to BVDFree. CONCLUSIONS: The findings provide a benchmark for the status of BVDV control in England; continued analysis of test results will be important to assess progress towards eradication.

BVD seroprevalence in the Irish cattle population as the national BVD programme progresses toward eradication.

BACKGROUND: Bovine Viral Diarrhoea Virus (BVDV) infection remains endemic in many countries worldwide. Ireland, in common with several other European counties, commenced an BVDV eradication programme in the last decade, Managing eradication programmes requires careful monitoring of diseases prevalence and understanding factors associated with disease exposure to ensure eradication programmes remain evidence based and tailored to the evolving epidemiological situation. METHODS: In this study, we explore the seroprevalence of BVDV exposure over a four-year period (2017 to 2020) in Ireland from a cohort of animals (n = 6,449) under 30 months of age sampled at slaughter, who were born subsequent to the commencement of a compulsory national eradication programme. Temporal trends and risk factor analysis were undertaken using multilevel logit regression models. RESULTS: There was a declining temporal trend in seroprevalence over the sample years of the study, and risk varied at both county- and herd-levels. The unadjusted marginal animal-level seroprevalence reduced from 9.1% in 2017 (95%; CI: 7.2-10.9) to 3.9% in 2020 (95%; CI: 3.2-4.6). The final model suggested that seropositivity in study cattle was strongly related with the presence of a PI animal in the herd during the year of the animal's birth, and to a lesser extent the status of the herd from which the animal was slaughtered. The risk of seroconversion increased significantly with increasing size of the herd of slaughter, in females relative to males, and in dairy relative to suckler herds. CONCLUSIONS: This study has shown that the BVDV serostatus of cattle at slaughter is correlated to the BVD infection history of the herd into which the animal was born and the herd from which it was slaughtered. Herd location, increased herd size and dairy production were associated with increased probability of serconversion. These findings will be used to inform the targeting of surveillance strategies once BVDV freedom has been achieved.

International proficiency trial for bovine viral diarrhea virus (BVDV) antibody detection: limitations of milk serology.

BACKGROUND: Control programs were implemented in several countries against bovine viral diarrhea (BVD), one of the most significant cattle diseases worldwide. Most of the programs rely on serological diagnostics in any phase of the program. For the detection of antibodies against BVD virus (BVDV), neutralization tests as well as a variety of (commercially available) ELISAs are used. Here, test systems applied in various laboratories were evaluated in the context of an international interlaboratory proficiency trial. A panel of standardized samples comprising five sera and five milk samples was sent to veterinary diagnostic laboratories (n=51) and test kit manufacturers (n=3). RESULTS: The ring trial sample panel was investigated by nine commercially available antibody ELISAs as well as by neutralization tests against diverse BVDV-1, BVDV-2 and/or border disease virus (BDV) strains. The negative serum and milk sample as well as a serum collected after BVDV-2 infection were mostly correctly tested regardless of the applied test system. A serum sample obtained from an animal immunized with an inactivated BVDV-1 vaccine tested positive by neutralization tests or by total antibody or Erns-based ELISAs, while all applied NS3-based ELISAs gave negative results. A further serum, containing antibodies against the ovine BDV, reacted positive in all applied BVDV ELISAs, a differentiation between anti-BDV and anti-BVDV antibodies was only enabled by parallel application of neutralization tests against BVDV and BDV isolates. For the BVDV antibody-positive milk samples (n=4), which mimicked prevalences of 20% (n=2) or 50% (n=2), considerable differences in the number of positive results were observed, which mainly depended on the ELISA kit and the sample incubation protocols used. These 4 milk samples tested negative in 43.6%, 50.9%, 3.6% and 56.4%, respectively, of all investigations. Overall, negative results occurred more often, when a short sample incubation protocol instead of an over-night protocol was applied. CONCLUSIONS: While the seronegative samples were correctly evaluated in most cases, there were considerable differences in the number of correct evaluations for the seropositive samples, most notably when pooled milk samples were tested. Hence, thorough validation and careful selection of ELISA tests are necessary, especially when applied during surveillance programs in BVD-free regions.

Output-based assessment of herd-level freedom from infection in endemic situations: Application of a Bayesian Hidden Markov model.

Countries have implemented control programmes (CPs) for cattle diseases such as bovine viral diarrhoea virus (BVDV) that are tailored to each country-specific situation. Practical methods are needed to assess the output of these CPs in terms of the confidence of freedom from infection that is achieved. As part of the STOC free project, a Bayesian Hidden Markov model was developed, called STOC free model, to estimate the probability of infection at herd-level. In the current study, the STOC free model was applied to BVDV field data in four study regions, from CPs based on ear notch samples. The aim of this study was to estimate the probability of herd-level freedom from BVDV in regions that are not (yet) free. We additionally evaluated the sensitivity of the parameter estimates and predicted probabilities of freedom to the prior distributions for the different model parameters. First, default priors were used in the model to enable comparison of model outputs between study regions. Thereafter, country-specific priors based on expert opinion or historical data were used in the model, to study the influence of the priors on the results and to obtain country-specific estimates. The STOC free model calculates a posterior value for the model parameters (e.g. herd-level test sensitivity and specificity, probability of introduction of infection) and a predicted probability of infection. The probability of freedom from infection was computed as one minus the probability of infection. For dairy herds that were considered free from infection within their own CP, the predicted probabilities of freedom were very high for all study regions ranging from 0.98 to 1.00, regardless of the use of default or country-specific priors. The priors did have more influence on two of the model parameters, herd-level sensitivity and the probability of remaining infected, due to the low prevalence and incidence of BVDV in the study regions. The advantage of STOC free model compared to scenario tree modelling, the reference method, is that actual data from the CP can be used and estimates are easily updated when new data becomes available.

[Genetic diversity and distribution of bovine pestiviruses (Flaviviridae: Pestivirus) in the world and in the Russian Federation].

The genus Pestivirus of the family Flaviviridae includes 11 species. Bovine pestiviruses are the causative agents of viral diarrhea/mucosal disease and include three genetically distinct species: pestivirus A (BVDV-1), B (BVDV-2), and H (BVDV-3). The number of BVDV-1 subtypes is 21, BVDV-2 - 4, and BVDV-3 - 4, which complicates the diagnosis of associated diseases, reduces the effectiveness of vaccination and control programs.We performed the search in the PubMed, Web of Science, Scopus, eLIBRARY.RU databases for articles published in 2000-2021.Pestivirus A is distributed everywhere, although the largest number of subtypes was found in cattle in Italy and China. The virus is widespread in the Central region of the Russia (subtypes 1a and 1m). In Siberia, eleven subtypes circulate among native and imported animals: 1a (5%), 1b (35%), 1c (5%), 1d (10%), 1f (20%), 1g, 1i (both 2.5%), 1j, 1k, 1p, and 1r (all for 5%). Pestivirus B subtype is more virulent, found less frequently and mainly in the North and South America, in some European countries, and in Asia. Three subtypes have been identified in Siberia: 2a (25%), 2b (10%), and 2c (5%). Pestivirus H circulates in Europe, Asia and South America. The main route of entry is contaminated biological products. In Russia, BVDV-3 of the Italian-Brazilian group (3a) was detected in 7 lots of fetal bovine serum.The role of the virus in the occurrence of respiratory diseases in calves, abortion, systemic infection and enteritis in calves and adult animals has been established. The source of the virus in such cases was a contaminated modified live vaccine.