Reproductive and economic impact following controlled introduction of cattle persistently infected with bovine viral diarrhea virus into a naive group of heifers

Exploring viral diversity and metagenomics in livestock: insights into disease emergence and spillover risks in cattle

Cattle have a significant impact on human societies in terms of both economics and health. Viral infections pose a relevant problem as they directly or indirectly disrupt the balance within cattle populations. This has negative consequences at the economic level for producers and territories, and also jeopardizes human health through the transmission of zoonotic diseases that can escalate into outbreaks or pandemics. To establish prevention strategies and control measures at various levels (animal, farm, region, or global), it is crucial to identify the viral agents present in animals. Various techniques, including virus isolation, serological tests, and molecular techniques like PCR, are typically employed for this purpose. However, these techniques have two major drawbacks: they are ineffective for non-culturable viruses, and they only detect a small fraction of the viruses present. In contrast, metagenomics offers a promising approach by providing a comprehensive and unbiased analysis for detecting all viruses in a given sample. It has the potential to identify rare or novel infectious agents promptly and establish a baseline of healthy animals. Nevertheless, the routine application of viral metagenomics for epidemiological surveillance and diagnostics faces challenges related to socioeconomic variables, such as resource availability and space dedicated to metagenomics, as well as the lack of standardized protocols and resulting heterogeneity in presenting results. This review aims to provide an overview of the current knowledge and prospects for using viral metagenomics to detect and identify viruses in cattle raised for livestock, while discussing the epidemiological and clinical implications.

Serosurvey and associated risk factors for bovine viral diarrhea virus infection in cattle in Egypt

Bovine viral diarrhea virus (BVDV), is widely spread, poses a considerable risk of infection in the majority of dairy farms, causing respiratory, gastrointestinal, and reproductive problems. The aim of this study was to determine the seroprevalence and the risk variables associated with the seroprevalence of BVDV infection in cattle in four Egyptian governorates. A total of 680 blood samples were collected from cattle and examined for the presence of antibodies against BVDV using indirect ELISA (iELISA). Reproductive and management factors were considered, and epidemiological surveys were conducted. The total seroprevalence of BVDV in cattle was 18.24% (124/680) and it was significantly higher in females 19.66% (116/590), cattle older than 8 years 22.14% (62/280), dairy animals 22.65% (94/514), introduction of new animals to herd 21.39% (89/416), breeding with artificial insemination 28.46% (74/260), animals with history of abortion 28.76% (49/357), or during lactation stage 23% (89/387). The present findings suggest that BVD is prevalent in Egyptian dairy cattle and has an impact on farm productivity and production. Therefore, older, lactating, and aborted animals should also be identified for the disease, pose a risk of infection, and be handled appropriately.

Identification of Genomic Instability in Cows Infected with BVD Virus

An important factor for dairy cattle farmers is the profitability of cattle rearing, which is influenced by the animals' health and reproductive parameters, as well as their genomic stability and integrity. Bovine viral diarrhea (BVD) negatively affects the health of dairy cattle and causes reproductive problems. The aim of the study was to identify genomic instability in cows with reproductive disorders following infection with the BVD virus. The material for analysis was peripheral blood from Holstein-Friesian cows with reproductive problems, which had tested positive for BVD, and from healthy cows with no reproductive problems, which had tested negative for BVD. Three cytogenetic tests were used: the sister chromatid exchange assay, fragile sites assay, and comet assay. Statistically significant differences were noted between the groups and between the individual cows in the average frequency of damage. The assays were good biomarkers of genomic stability and enabled the identification of individuals with an increased frequency of damage to genetic material that posed a negative impact on their health. The assays can be used to prevent disease during its course and evaluate the genetic resistance of animals. This is especially important for the breeder, both for economic and breeding reasons. Of the three assays, the comet assay proved to be the most sensitive for identifying DNA damage in the animals.

Seroprevalence and risk factors associated with bovine viral diarrhoea virus in Turkey

Bovine viral diarrhoea virus (BVDV) is an infectious agent that is extensively observed worldwide and is among the crucial pathogens of the cattle industry. BVDV infection causes gastrointestinal and respiratory diseases. This study aimed to determine the seropositivity and associated potential risk factors for the risk assessment of BVDV infection in the dairy cattle population in the Aegean Region of Turkey. In this cross-sectional study, 552 serum samples were collected between August 2018 and September 2019 from 48 herds that were not vaccinated against BVDV. Farmers were interviewed using a questionnaire on potential BVDV risk factors. BVDV-specific antibodies in serum samples were detected using a commercial indirect-ELISA kit. The herd-level and animal-level prevalence of BVDV seropositivity was 89.58% (95% CI: 77.83-95.47) and 48.37% (95% CI: 44.23-52.54), respectively. The multivariable logistic regression model analysis demonstrated a positive correlation between BVDV infection and age, common pasture use with small ruminants, the use of natural insemination, and history of respiratory and/or reproduction problems. The results of this study showed that BVDV infection is common in dairy herds in the Aegean Region. The risk assessment would aid the implementation of a voluntary control programme for BVDV in this region.

Temporal analysis of bovine pestivirus diversity in Brazil

In this study, phylogenetic and evolutionary analyses of cattle pestiviruses (BVDV-1, 2 and HoBiPeV) originating in Brazil were used to investigate the temporal diversification of subgenotypes in the country. Inferred dated phylogeny and time of the most recent common ancestor (tMRCA) demonstrated that some BVDV subgenotypes (1a, 1b, 1d, 1e, and 2b) and HoBi-like sequences clustered according to the region in which they were collected and that the diversification of subgenotypes appears to have occurred around the introduction of first Bos taurus and then Bos indicus, followed by expansion to form the adapted Brazilian breeds. The present results help to elucidate the temporal facts that led to diversification of ruminant pestiviruses in cattle in Brazil.

Use of multivariate analysis to evaluate antigenic relationships between US BVDV vaccine strains and non-US genetically divergent isolates

Bovine viral diarrhea virus (BVDV) comprises two species, BVDV-1 and BVDV-2. But given the genetic diversity among pestiviruses, at least 22 subgenotypes are described for BVDV-1 and 3-4 for BVDV-2. Genetic characterization is generally accomplished through complete or partial sequencing and phylogeny, but it is not a reliable method to define antigenic relationships. The traditional method for evaluating antigenic relationships between pestivirus isolates is the virus neutralization (VN) assay, but interpretation of the data to define antigenic relatedness can be difficult to discern for BVDV isolates within the same BVDV species. Data from this study utilized a multivariate analysis for visualization of VN results to analyze the antigenic relationships between US vaccine strains and field isolates from Switzerland, Italy, Brazil, and the UK. Polyclonal sera were generated against six BVDV strains currently contained in vaccine formulations, and each serum was used in VNs to measure the titers against seven vaccine strains (including the six homologous strains) and 23 BVDV field isolates. Principal component analysis (PCA) was performed using VN titers, and results were interpreted from PCA clustering within the PCA dendrogram and scatter plot. The results demonstrated clustering patterns among various isolates suggesting antigenic relatedness. As expected, the BVDV-1 and BVDV-2 isolates did not cluster together and had the greatest spatial distribution. Notably, a number of clusters representing antigenically related BVDV-1 subgroups contain isolates of different subgenotypes. The multivariate analysis may be a method to better characterize antigenic relationships among BVDV isolates that belong to the same BVDV species and do not have distinct antigenic differences. This might be an invaluable tool to ameliorate the composition of current vaccines, which might well be important for the success of any BVDV control program that includes vaccination in its scheme.

Antibody Response to a Live-Modified Virus Vaccine against Bovine Viral Diarrhoea in Dairy Cattle in a Field Trial

(1) Background: The objective of the study was to evaluate the long-term antibody response of dairy cows to a single dose of a commercial modified-live virus (MLV) vaccine against bovine viral diarrhea (Mucosiffa^® CEVA Sante Animale, Liburne, France). (2) Methods: The study was carried out in a dairy cattle herd counting 290 animals negative for bovine viral diarrhoea virus (BVDV). The vaccination was implemented following the manufacturer’s instructions. Twelve dairy cows were randomly selected before the study, and blood samples were collected right before the vaccination and then 12 times at 1-month intervals. The serum samples were screened using a virus neutralization test (VNT) and ELISA. (3) Results: Both tests showed that antibody titers increased significantly in all animals within the first month post-vaccination, and continued to increase significantly until the second (VNT) and third (ELISA) month post-vaccination. Antibody titers remained high and stable until the end of the study. Moreover, cows did not show any adverse reactions or clinical symptoms of the disease. (4) Conclusion: The results of this study indicated that the administration of one dose MLV vaccine was able to stimulate long-lasting (12-months) and strong antibody response in all vaccinated cows.

Infection with Bovine Viral Diarrhea Virus in Cattle in Southern Papua, Indonesia

The aim of this preliminary study was to determine the prevalence of Bovine Viral Diarrhea Virus (BVDV) and its association with reproductive problems in cattle in Timika, Southern Papua, Indonesia, an emerging area for beef production. Serum from 77 beef cattle was collected from four villages and tested, using both antibody and antigen ELISA kits for BVDV. Data of the villages of origin, age, breed, sex and the number of parities of the cattle were collected. The pregnancy status of the cattle was determined by rectal examination. Results showed that the prevalence of BVDV antibody in individual cattle in Timika was 11.7% (CI: 6.1 - 20.0%), while at the farm level the antibody prevalence was 18.4% (CI: 8.9 - 33.7%).). Seropositivity for BVDV increased with age (P=0.02), from 0% (CI: 0 - 37.2%) in less than two-years old to 28.6% (CI: 11.3 - 55.0%) in cattle older than eight years of age. BVDV antibody was 2.9 times more prevalent in non-pregnant cows than in antibody negative cows (CI: 1.02 - 8.14, P=0.04). BVD antigen was not detected in the present study. This study reported for the first time, evidence of infection with BVDV in cattle in Papua and indicated that BVDV infection may be associated with infertility.

Multivariate analysis as a method to evaluate antigenic relationships between BVDV vaccine and field strains

Bovine viral diarrhea virus (BVDV) is comprised of two species, BVDV-1 and BVDV-2, but given the genetic diversity among pestiviruses, at least 21 subgenotypes are described for BVDV-1 and 4 for BVDV-2. Genetic characterization can be achieved through complete or partial sequencing and phylogeny, but antigenic characterization can be difficult to determine due to the antigenic diversity and cross-neutralization that exists among isolates. The traditional method for evaluating antigenic relationships between pestivirus isolates is the virus neutralization (VN) assay, but interpretation of the data to determine antigenic difference can be unclear. Data from this study utilized a multivariate analysis for visualization of VN results to analyze the antigenic relationships between vaccine strains and multiple field isolates. Polyclonal sera were generated against 6 BVDV strains currently contained in vaccine formulations, and each serum was used in VN's to measure the neutralizing antibody titers against 15 BVDV field isolates characterized as prevalent and divergent subgenotypes in the USA. Principal component analysis (PCA) were performed on the VN assay datasets, and results were interpreted from PCA clustering within the PCA dendrogram and scatter plot. The results demonstrated clustering patterns among isolates suggestive of antigenic differences. While expected, the BVDV-1 and BVDV-2 isolates did not cluster together and had the greatest spatial distribution. In addition, other BVDV isolates had distinct spatial patterns suggesting antigenically divergent isolates. This analysis provides an alternative and more efficient means to analyze large VN datasets to visualize antigenic relationships between pestivirus isolates. This analysis could be beneficial for vaccine development and evaluation of efficacy, since most vaccines cannot fully protect animals from the broad range diversity of BVDV viruses.

Importance of Viral Disease in Dairy Cow Fertility

Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence that viral infections have additional actions in dairy cows, which are reflected in reduced conception rates. These effects are, however, highly dependent on the time at which an individual animal first contracts the disease and are less easy to quantify. This paper reviews the evidence relating to five viruses that can affect fertility, together with their potential mechanisms of action. Acute infection with non-cytopathic bovine viral diarrhea virus (BVDV) in mid-gestation increases abortion rates or causes the birth of persistently infected calves. BVDV infections closer to the time of breeding can have direct effects on the ovaries and uterine endometrium, which cause estrous cycle irregularities and early embryo mortality. Fertility may also be reduced by BVDV-induced immunosuppression, which increases the susceptibility to bacterial infections. Bovine herpesvirus (BHV)-1 is most common in pre-pubertal heifers, and can slow their growth, delay breeding, and increase the age at first calving. Previously infected animals subsequently show reduced fertility. Although this may be associated with lung damage, ovarian lesions have also been reported. Both BHV-1 and BHV-4 remain latent in the host following initial infection and may be reactivated later by stress, for example associated with calving and early lactation. While BHV-4 infection alone may not reduce fertility, it appears to act as a co-factor with established bacterial pathogens such as Escherichia coli and Trueperella pyogenes to promote the development of endometritis and delay uterine repair mechanisms after calving. Both Schmallenberg virus (SBV) and bluetongue virus (BTV) are transmitted by insect vectors and lead to increased abortion rates and congenital malformations. BTV-8 also impairs the development of hatched blastocysts; furthermore, infection around the time of breeding with either virus appears to reduce conception rates. Although the reductions in conception rates are often difficult to quantify, they are nevertheless sufficient to cause economic losses, which help to justify the benefits of vaccination and eradication schemes.

Mucosal disease-like lesions caused by HoBi-like pestivirus in Brazilian calves in 2010-2011: Clinical, pathological, immunohistochemical, and virological characterization

A HoBi-like pestivirus was first described in 2004 in a Brazilian fetal bovine serum that was exported to Germany. Nevertheless, it is believed that the virus had been present since the 1990's, when it was detected in buffalos of Brazilian origin. Reproductive and respiratory diseases have been reported since 2001 in cattle, and more recently, diseases accompanied by a clinical presentation of mucosal disease-like (MD-like lesions have been reported as well. In the present study, the authors reported the oldest case of MD--like in cattle, associated with a HoBi-like pestivirus infection. Diarrhea, anorexia, nasal discharge, hypersalivation, and weakness were observed in 20 calves. For two of the animals, clinical follow-ups were performed. Following their death, necropsy was performed on these two calves. The main gross alterations observed were ulcers and erosions in the upper and lower digestive tract and interdigital dermatitis. Clinical history, gross findings, histopathological examination, immunohistochemistry, RT-PCR, and virus isolation were determined as suitable tools for the diagnosis of a MD-like outbreak, caused by a HoBi-like pestivirus.

Spatial analysis for bovine viral diarrhea virus and bovine herpesvirus type 1 infections in the state of Paraíba, northeastern Brazil

BACKGROUND

Bovine Viral Diarrhea Virus (BVDV) and Bovine Herpesvirus type 1 (BoHV-1) cause reproductive problems in cattle and restrictions on international trade in animals worldwide. Both infections were detected in cattle herds in the Paraíba state, Northeastern Brazil, however, the spatial distribution and geographic identification of positive herds for these viruses has never been examined. Therefore, the aim of this study was to describe the spatial pattern of apparent prevalence estimate and to identify spatial clustering of positive herds of BVDV and BoHV-1 infections in cattle herds from the state of Paraíba, Northeastern Brazil.

RESULTS

The herd-level prevalence for BVDV and BoHV-1 infections in Paraíba were, respectively, 65.5% (95% CI: 61.1-69.7) and 87.8% (95% CI: 84.5-90.5). The average apparent within-herd prevalence of BVDV was 31.8% and of BoHV-1 was 62.4%. The predicted prevalence was highest (0.42-0.75) for BVDV in the west, north and eastern part of Sertão and in the central and eastern part of Agreste/Zona da Mata. For BoHV-1, the highest predicted prevalence (0.74-0.97) was in some local areas across Sertão and throughout the eastern part of Agreste/Zona da Mata. Six significant clusters were detected for BVDV, a primary cluster covering the eastern Sertão region, with 11 herds, radius of 24.10 km and risk relative (RR) of 2.21 (P <  0.001) and five smaller significant clusters, involving one or two herds in Agreste/Zona da Mata region with a high RR. A significant clustering of BoHV-1 positive herds (P <  0.001) was detected in Agreste/Zona da Mata region with a radius of 77.17 km and a RR of 1.27, with 103 cases. Consistency was found between kriging and SatScan results for identification of risk areas for BVDV and BoHV-1 infections.

CONCLUSIONS

The clusters detected contemplated different areas of the state, with BVDV cluster located in the Sertão and BoHV-1 in Agreste/Zona da Mata stratum. Through the risk mapping, it was possible to identify the areas in which the risk is significantly elevated, coincided with areas where there are borders with other states and in which there is a high movement of animals.

Perspective on BVDV control programs

Programs for control and eradication of bovine viral diarrhea virus (BVDV) are often considered prudent when the expense of a control program within a specified time frame effectively prevents loss due to disease and the expense of control does not exceed the costs associated with infection. In some geographic areas, concerns about animal welfare or desires to reduce antibiotic usage may motivate BVDV control even when control programs are associated with a lack of financial return on investment. In other geographic areas, concerns about financial return on investment may be the key motivating factor in considering implementation of BVDV control programs. Past experiences indicate that systematic, well-coordinated control programs have a clear potential for success, while voluntary control programs in cultures of distributed decision-making often result in notable initial progress that ultimately ends in dissolution of efforts. Segmentation of the cattle industry into cow-calf producers, stocker/backgrounders, and feedlot operators amplifies the distribution of decision-making regarding control programs and may result in control measures for one industry segment that are associated with significant costs and limited rewards. Though the host range of BVDV extends well beyond cattle, multiple eradication programs that focus only on testing and removal of persistently infected (PI) cattle have proven to be effective in various countries. While some individuals consider education of producers to be sufficient to stimulate eradication of BVDV, research surrounding the adoption of innovative health care procedures suggests that the process of adopting BVDV control programs has a social element. Collegial interactions and discussions may be crucial in facilitating the systematic implementation necessary to optimize the long-term success of control programs. Compulsory control programs may be considered efficient and effective in some regions; however, in a nation where individual identification of cattle remains voluntary, the likelihood of effective compulsion to control BVDV within a farm or ranch appears to be very unlikely. While currently available diagnostic tests are sufficient to support BVDV eradication via systematic, well-coordinated programs, the development of a diagnostic procedure to safely and consistently detect the gestation of a PI fetus after 5 months of gestation would be a valuable research breakthrough. This desired testing modality would allow diagnosis of PI calves, while the dam continues to provide biocontainment of the infected fetus. This development could speed the progress of control programs in achieving the goal of BVDV control and eventual eradication.

Comparison of the breadth and complexity of bovine viral diarrhea (BVDV) populations circulating in 34 persistently infected cattle generated in one outbreak

Exposure to bovine viral diarrhea viruses (BVDV) results in acute and persistent infections. Persistent infections result from in utero exposure during the first trimester of gestation. Clinical presentation, in persistently infected cattle (PI), is highly variable. The reasons for this variation is largely unknown. The BVDV circulating in PI exist as quasispecies (swarms of individual viruses). An outbreak resulting in 34 PI cattle presented an opportunity to compare a large number of PI׳s. Methods were developed to compare the circulating viral populations within PI animals. It was found that PI animals generated in the same outbreak carry circulating viral populations that differ widely in size and diversity. Further, it was demonstrated that variation in PI viral populations could be used as a quantifiable phenotype. This observation makes it possible to test the correlation of this phenotype to other phenotypes such as growth rate, congenital defects, viral shed and cytokine expression.

Serum antibodies from a subset of horses positive for Babesia caballi by competitive enzyme-linked immunosorbent assay demonstrate a protein recognition pattern that is not consistent with infection

Tick-borne pathogens that cause persistent infection are of major concern to the livestock industry because of transmission risk from persistently infected animals and the potential economic losses they pose. The recent reemergence of Theileria equi in the United States prompted a widespread national survey resulting in identification of limited distribution of equine piroplasmosis (EP) in the U.S. horse population. This program identified Babesia caballi-seropositive horses using rhoptry-associated protein 1 (RAP-1)-competitive enzyme-linked immunosorbent assay (cELISA), despite B. caballi being considered nonendemic on the U.S. mainland. The purpose of the present study was to evaluate the suitability of RAP-1-cELISA as a single serological test to determine the infection status of B. caballi in U.S. horses. Immunoblotting indicated that sera from U.S. horses reacted with B. caballi lysate and purified B. caballi RAP-1 protein. Antibody reactivity to B. caballi lysate was exclusively directed against a single ∼50-kDa band corresponding to a native B. caballi RAP-1 protein. In contrast, sera from experimentally and naturally infected horses from regions where B. caballi is endemic bound multiple proteins ranging from 30 to 50 kDa. Dilutions of sera from U.S. horses positive by cELISA revealed low levels of antibodies, while sera from horses experimentally infected with B. caballi and from areas where B. caballi is endemic had comparatively high antibody levels. Finally, blood transfer from seropositive U.S. horses into naive horses demonstrated no evidence of B. caballi transmission, confirming that antibody reactivity in cELISA-positive U.S. horses was not consistent with infection. Therefore, we conclude that a combination of cELISA and immunoblotting is required for the accurate serodiagnosis of B. caballi.