The Contribution of Infections with Bovine Viral Diarrhea Viruses to Bovine Respiratory Disease

Investigating nutritional strategies during a rest period to improve health, growth, and behavioral outcomes of transported surplus dairy calves

The objective of this study was to investigate the effects of feeding surplus dairy calves a milk replacer (MR) or one of 2 different oral rehydration solutions (ORS) during a midtransportation rest period on metabolic and clinical health indicators, growth, and behavioral outcomes after arrival at a calf-raising facility. Surplus dairy calves (n = 128) were transported in 4 cohorts from February to July 2022 for 12 h to a holding facility, rested for 8 h, then transported for an additional 6 h to a calf-raising facility. Upon arrival at the holding facility, calves were randomly assigned to 1 of 3 treatments: MR (n = 43), a high-sodium ORS developed for diarrhea (ORS-D; n = 43), or a high-potassium ORS developed for transportation (ORS-T; n = 42). The exact age of calves at transportation was unknown; however, all calves were less than 14 d of age. Calf BW at enrollment was 43.9 ± 5.9 kg, 43.7 ± 6.5 kg, and 45.0 ± 4.5 kg for calves fed MR, ORS-D, and ORS-T, respectively. Calves were fed 2.0 L of their treatment twice, once upon arrival and once before leaving the holding facility. At unloading and reloading at the holding facility, calves were weighed and blood samples were obtained. Calves were also health scored at unloading at the holding facility. After arrival at the calf-raising facility, calves were weighed, health scored, and blood samples were taken. Blood samples were collected at 24 and 48 h and BW was recorded at 24 h, 48 h, 72 h, 5 d, 7 d, 14 d, and at 8 wk after arrival at the calf-raising facility. Calves were also health scored daily for 14 d; health scoring included fecal consistency scoring and evaluating the presence or absence of respiratory disease. Lying time, lying bouts, and activity index were measured during transportation and from 3 d relative to transportation using accelerometers. At arrival to the calf-raiser, calves fed ORS-D had higher concentrations of nonesterified fatty acids (NEFA) and BHB than calves fed MR. Furthermore, calves fed ORS-T had higher concentrations of BHB at arrival to the calf raiser compared with calves fed MR. In the 14 d after arrival at the calf-raiser, there was evidence that calves fed ORS-T had a higher proportion of days with diarrhea and respiratory disease compared with those fed MR. During transportation, calves fed ORS-T had a lower activity index than calves fed MR, suggesting that ORS-T calves had lower overall activity. In addition, on the day of transportation (d 0), ORS-T and ORS-D calves had a lower activity index than calves fed MR. There were no treatment effects on growth outcomes. The results of this study suggest that feeding MR rather than an ORS during a midtransportation rest period could minimize fat mobilization and can potentially improve diarrhea and respiratory disease but does not affect growth outcomes after arrival at calf-raisers.

First evaluation of the impact of a targeted subunit vaccine against bovine viral diarrhea virus in feedlot cattle

Bovine respiratory disease (BRD) is a serious health and economic problem in the beef industry, which is often associated with transportation and caused by different pathogens. In this study, we evaluated the effect of a novel subunit targeted vaccine against bovine viral diarrhea virus (BVDV) in feedlot cattle, a major viral agent of BRD. The core of this novel vaccine is the fusion of the BVDV structural glycoprotein, E2, to a single-chain antibody, APCH, together termed, APCH-E2. The APCH antibody targets the E2 antigen to the major histocompatibility type II molecule (MHC-II) present in antigen-presenting cells. To evaluate the vaccine, 2,992 animals were randomly allocated into two groups, control group (N = 1,491) and treatment group (N = 1,501). Animals of both groups received the routine sanitary plan: two doses of clostridial, respiratory, and rabies vaccines. Animals within the treatment group also received two doses of a targeted subunit vaccine against BVDV. Serum samples were taken on the day of the first inoculation (T0) and 90 d later (T90). Viral circulation was monitored using an anti-P80 ELISA (virus-specific) and immune response was evaluated by anti-E2 ELISA (detects virus and vaccine immune responses). Only animals treated for respiratory disease were considered positive cases of BRD. Results demonstrate that the control group had significantly more animals treated for BRD cases compared to the treatment group (5.9% vs. 3.7%, P = 0.02). The control group had a greater number of animals positive for anti-P80 antibodies and significantly fewer animals positive for anti-E2 antibodies compared to the treatment group (69% vs. 61% and 71% vs. 99%, respectively, P = 0.003), consistent with natural viral circulation within this group. The treatment group, conversely, had fewer animals positive for anti-P80 antibodies and a greater number of animals positive for anti-E2 antibodies, consistent with a robust vaccine-induced antibody response and a reduction of the BVDV circulation within this group. The data indicate the new subunit targeted vaccine induced greater anti-E2 antibodies and reduced the amount of BVD virus circulation within the treatment group leading to a fewer number of animals needing to be treated for BRD.

Mannheimia haemolytica Negatively Affects Bovine Herpesvirus Type 1.1 Replication Capacity In Vitro

Bovine Respiratory Disease (BRD) is a multifactorial condition affecting cattle worldwide resulting in high rates of morbidity and mortality. The disease can be triggered by Bovine Herpesvirus-1 (BoHV-1) infection, stress, and the subsequent proliferation and lung colonization by commensal bacteria such as Mannheimia haemolytica, ultimately inducing severe pneumonic inflammation. Due to its polymicrobial nature, the study of BRD microbes requires co-infection models. While several past studies have mostly focused on the effects of co-infection on host gene expression, we focused on the relationship between BRD pathogens during co-infection, specifically on M. haemolytica’s effect on BoHV-1 replication. This study shows that M. haemolytica negatively impacts BoHV-1 replication in a dose-dependent manner in different in vitro models. The negative effect was observed at very low bacterial doses while increasing the viral dose counteracted this effect. Viral suppression was also dependent on the time at which each microbe was introduced to the cell culture. While acidification of the culture medium did not grossly affect cell viability, it significantly inhibited viral replication. We conclude that M. haemolytica and BoHV-1 interaction is dose and time-sensitive, wherein M. haemolytica proliferation induces significant viral suppression when the viral replication program is not fully established.

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.

Recombinant Bovine Herpesvirus Type I Expressing the Bovine Viral Diarrhea Virus E2 Protein Could Effectively Prevent Infection by Two Viruses

Bovine respiratory disease complex (BRDC) is a comprehensive disease in cattle caused by various viral and bacterial infections. Among them, bovine herpesvirus type I (BoHV−1) and bovine viral diarrhea virus (BVDV) play important roles and have caused huge financial losses for the cattle industry worldwide. At present, vaccines against BRDC include trivalent attenuated BoHV−1, BVDV−1, and BVDV−2 live vaccines, BoHV−1 live attenuated vaccines, and BoHV−1/BVDV bivalent live attenuated vaccines, which have limitations in terms of their safety and efficacy. To solve these problems, we optimized the codon of the BVDV−1 E2 gene, added the signal peptide sequence of the BoHV−1 gD gene, expressed double BVDV−1 E2 glycoproteins in tandem at the BoHV−1 gE gene site, and constructed a BoHV−1 genetics-engineered vectored vaccine with gE gene deletion, named BoHV−1 gE/E2−Linker−E2⁺ and BoHV−1 ΔgE. This study compared the protective effects in BoHV−1, BoHV−1 ΔgE, BoHV−1 gE/E2−Linker−E2⁺, and BVDV−1 inactivated antigen immunized guinea pigs and calves. The results showed that BoHV−1 gE/E2−Linker−E2⁺ could successfully induce guinea pigs and calves to produce specific neutralizing antibodies against BVDV−1. In addition, after BoHV−1 and BVDV−1 challenges, BoHV−1 gE/E2−Linker−E2⁺ can produce a specific neutralizing antibody response against BoHV−1 and BVDV−1 infections. Calves immunized with this type of virus can be distinguished as either vaccinated animals (gE^-) or naturally infected animals (gE⁺). In summary, our data suggest that BoHV−1 gE/E2−Linker−E2⁺ and BoHV−1 ΔgE have great potential to prevent BVDV−1 or BoHV−1 infection.

HoBi-like pestivirus in 2 cases of fatal respiratory disease of feedlot cattle in Argentina

HoBi-like pestivirus (HoBiPeV) is an emerging virus that has been detected in cattle and other ruminants. We diagnosed 2 cases of fatal bovine respiratory disease complex (BRDC) associated with infection with HoBiPeV in a feedlot in Argentina. The main findings in 2 steers autopsied were interstitial bronchopneumonia (case 1) and fibrinous bronchopneumonia (case 2). HoBiPeV was detected by RT-PCR in lungs of both animals and by immunohistochemistry in case 2. Phylogenetic analysis showed that both strains clustered within the "Brazilian-Italian" clade. In case 2, Mannheimia haemolytica was isolated from the lung. There is scant information about the contribution of HoBiPeV to the pathogenesis of BRDC. To our knowledge, HoBiPeV has not been reported previously in association with M. haemolytica pneumonia. Our findings further support the involvement of HoBiPeV in cases of BRDC and contribute to understanding the synergy of this etiologic agent in the pathogenesis of BRD, which is critical for the development of appropriate preventive strategies.

Bovine Respiratory Disease Considerations in Young Dairy Calves

Raising young dairy calves presents many challenges for producers and veterinarians including losses attributable to BRD. This article will discuss several key concepts for practitioners to consider when applying evidence-based medicine for the control and treatment of BRD in young dairy calves. The authors review BRD complex, provide considerations for diagnostic approaches, and discuss research associated with the control and treatment of BRD.

Modeling the Effect of Bovine Viral Diarrhea Virus in Australian Beef Herds

Bovine viral diarrhea virus (BVDV) is an economically important disease in Australian beef farming. The disease typically results in low-level production losses that can be difficult to detect for several years. Simulation modeling can be used to support the decision to control BVDV; however, current BVDV simulation models do not adequately reflect the extensive farming environment of Australian beef production. Therefore, the objective of this study was to develop a disease simulation model to explore the impact of BVDV on beef cattle production in south-east Australia. A dynamic, individual-based, stochastic, discrete-time simulation model was created to simulate within-herd transmission of BVDV in a seasonal, self-replacing beef herd. We used the model to simulate the effect of herd size and BVDV introduction time on disease transmission and assessed the short- and long-term impact of BVDV on production outputs that influence the economic performance of beef farms. We found that BVDV can become established in a herd after a single PI introduction in 60% of cases, most frequently associated with the breeding period. The initial impact of BVDV will be more severe in smaller herds, although self-elimination is more likely in small herds than in larger herds, in which there is a 23% chance that the virus can persist for >15 years following a single incursion in a herd with 800 breeders. The number and weight of steers sold was reduced in the presence of BVDV and the results demonstrated that repeat incursions exacerbate long-term production losses, even when annual losses appear marginal. This model reflects the short- and long-term production losses attributed to BVDV in beef herds in southeast Australia and provides a foundation from which the influence and economic utility of BVDV prevention in Australian beef herds can be assessed.

Etiology and risk factors for bovine respiratory disease in pre-weaned calves on California dairies and calf ranches

Our study objective was to estimate the magnitude of association of BRD risk factors including failure of passive immunity transfer, sex, age, and the detection of suspected BRD etiological pathogens in pre-weaned dairy calves in California. A conditional logistic regression model and a mixed-effects logistic regression model were used to estimate the association of these potential risk factors with BRD from a matched and nested case-control studies, respectively. For each exposure covariate, the odds ratio (OR) is the ratio of odds of an exposure in a BRD calf (case) to that in a non-BRD calf (control). In the matched case-control study, an interaction term between failure of transfer of passive immunity and sex of calf showed that female calves were more negatively impacted by failure of transfer of passive immunity compared to male calves. The odds ratios comparing failure of transfer of passive immunity in BRD score positive calves versus controls for male calves was 1.34 (95 % CI: 0.87, 2.06) and was 2.47 (95 % CI: 1.54, 3.96) for female calves. The model odds ratios varied from 1.74 (95 % CI: 1.26, 2.42) for Mycoplasma spp. to 9.18 (95 % CI: 2.60, 32.40) for Histophilus somni, with Mannheimia haemolytica and Pasteurella multocida having an OR of 6.64 (95 % CI: 4.39, 10.03) and 6.53 (95 % CI: 4.44, 9.59), respectively. For bovine respiratory syncytial virus positive calves, the OR was 4.60 (95 % CI: 3.04, 6.97). Findings from the nested case-control study showed that based on thoracic ultrasonography findings consistent with BRD, the odds of a calf being 1 day older compared to a day younger were 1.01 (95 % CI: 1.00, 1.02) among BRD cases. For the bacterial and viral pathogens, the OR for Mycoplasma spp. and Pasteurella multocida were 1.85 (95 % CI: 1.24, 2.75) and 1.86 (95 % CI: 1.28, 2.71), respectively. The OR values for these pathogens were similar when both thoracic auscultation and ultrasound findings were used to detect cases of BRD. Based on positive scores for BRD using the California BRD scoring system, the OR for facility type, calf ranch versus dairy farm, was 3.17 (95 % CI: 1.43, 7.01), Mannheimia haemolytica was 3.50 (95 % CI: 2.00, 6.11), Pasteurella multocida was 1.78 (95 % CI: 1.21, 2.60), and bovine coronavirus was 2.61 (95 % CI: 1.85, 3.70). Results from both study designs showed the difference in relative contributions of age, sex, immune status, and pathogens in BRD occurrence between cases and controls in pre-weaned dairy calves.

Epidemiology of Bovine Pestiviruses Circulating in Italy

Pestiviruses are widespread and economically important pathogens of cattle and other animals. Pestivirus A (formerly known as Bovine viral diarrhea virus 1, BVDV-1), Pestivirus B (Bovine viral diarrhea virus 2, BVDV-2), and Pestivirus H (HoBi-like pestivirus, HoBiPeV) species are infecting primarily cattle. Like other RNA viruses, pestiviruses are characterized by a high degree of genetic variability. This high rate of variability is revealed by the existence of a number of viral subgenotypes within each species. In cattle, the highest number of pestivirus subgenotypes has been documented in European countries, particularly in Italy. The aim of this review is to report an up-to-date overview about the genetic diversity of pestiviruses in Italian cattle herds. All three bovine pestiviruses species have been identified in cattle population with variable frequency and geographical distribution. The genetic diversity of Italian pestiviral strains may have diagnostic and immunological implications, affecting the performance of diagnostic tools and the full cross-protection elicited by commercially available vaccines. Implementation and strengthening of coordinated approaches for bovine pestivirus control in Italy are recommended. Therefore, it would be extremely important to increase control and restriction measures to the trade of cattle and biological products of bovine origin, including those containing fetal bovine serum.

Novel Potent IFN-γ-Inducing CD8+ T Cell Epitopes Conserved among Diverse Bovine Viral Diarrhea Virus Strains

Studies of immune responses elicited by bovine viral diarrhea virus (BVDV) vaccines have primarily focused on the characterization of neutralizing B cell and CD4⁺ T cell epitopes. Despite the availability of commercial vaccines for decades, BVDV prevalence in cattle has remained largely unaffected. There is limited knowledge regarding the role of BVDV-specific CD8⁺ T cells in immune protection, and indirect evidence suggests that they play a crucial role during BVDV infection. In this study, the presence of BVDV-specific CD8⁺ T cells that are highly cross-reactive in cattle was demonstrated. Most importantly, novel potent IFN-γ-inducing CD8⁺ T cell epitopes were identified from different regions of BVDV polyprotein. Eight CD8⁺ T cell epitopes were identified from the following structural BVDV Ags: E^rns, E1, and E2 glycoproteins. In addition, from nonstructural BVDV Ags N^pro, NS2-3, NS4A-B, and NS5A-B, 20 CD8⁺ T cell epitopes were identified. The majority of these IFN-γ-inducing CD8⁺ T cell epitopes were found to be highly conserved among more than 200 strains from BVDV-1 and -2 genotypes. These conserved epitopes were also validated as cross-reactive because they induced high recall IFN-γ⁺CD8⁺ T cell responses ex vivo in purified bovine CD8⁺ T cells isolated from BVDV-1- and -2-immunized cattle. Altogether, 28 bovine MHC class I-binding epitopes were identified from key BVDV Ags that can elicit broadly reactive CD8⁺ T cells against diverse BVDV strains. The data presented in this study will lay the groundwork for the development of a contemporary CD8⁺ T cell-based BVDV vaccine capable of addressing BVDV heterogeneity more effectively than current vaccines.

BoHV-1-Vectored BVDV-2 Subunit Vaccine Induces BVDV Cross-Reactive Cellular Immune Responses and Protects against BVDV-2 Challenge

The bovine respiratory disease complex (BRDC) remains a major problem for both beef and dairy cattle industries worldwide. BRDC frequently involves an initial viral respiratory infection resulting in immunosuppression, which creates a favorable condition for fatal secondary bacterial infection. Current polyvalent modified live vaccines against bovine herpesvirus type 1(BoHV-1) and bovine viral diarrhea virus (BVDV) have limitations concerning their safety and efficacy. To address these shortcomings and safety issues, we have constructed a quadruple gene mutated BoHV-1 vaccine vector (BoHV-1 QMV), which expresses BVDV type 2, chimeric E2 and Flag-tagged Erns-fused with bovine granulocyte monocyte colony-stimulating factor (GM-CSF) designated here as QMV-BVD2*. Here we compared the safety, immunogenicity, and protective efficacy of QMV-BVD2* vaccination in calves against BVDV-2 with Zoetis Bovi-shield Gold 3 trivalent (BoHV-1, BVDV types 1 and 2) vaccine. The QMV-BVD2* prototype subunit vaccine induced the BoHV-1 and BVDV-2 neutralizing antibody responses along with BVDV-1 and -2 cross-reactive cellular immune responses. Moreover, after a virulent BVDV-2 challenge, the QMV-BVD2* prototype subunit vaccine conferred a more rapid recall BVDV-2-specific neutralizing antibody response and considerably better recall BVDV types 1 and 2-cross protective cellular immune responses than that of the Zoetis Bovi-shield Gold 3.

Evolution of the Seroprevalence of Pestivirus and Respiratory Viral Infections in Spanish Feedlot Lambs

The presence of respiratory viruses and pestiviruses in sheep has been widely demonstrated, and their ability to cause injury and predispose to respiratory processes have been proven experimentally. A longitudinal observational study was performed to determine the seroprevalence of bovine parainfluenza virus type 3 (BPIV-3), bovine respiratory syncytial virus (BRSV), bovine herpesvirus type 1 (BHV-1) and pestiviruses in 120 lambs at the beginning and the end of the fattening period. During this time, the animals were clinically monitored, their growth was recorded, and post-mortem examinations were performed in order to identify the presence of pneumonic lesions in the animals. Seroconversion to all viruses tested except BHV-1 was detected at the end of the period. Initially, BPIV-3 antibodies were the most frequently found, while the most common seroconversion through the analysed period occurred to BRSV. Only 10.8% of the lambs showed no detectable levels of antibodies against any of the tested viruses at the end of the survey. In addition, no statistical differences were found in the presentation of respiratory clinical signs, pneumonic lesions nor in the production performance between lambs that seroconverted and those which did not, except in the case of pestiviruses. The seroconversion to pestiviruses was associated with a reduction in the final weight of the lambs.

HoBi-Like Pestivirus and Reproductive Disorders

HoBi-like pestivirus (HoBiPeV) is an emerging group of pestiviruses that has been detected in cattle and other ruminants in South America, Europe, and Asia. Analogous to other bovine pestiviruses, namely bovine viral diarrhea (BVDV) 1 and 2, HoBiPeV is able to cause a variety of clinical forms that range from asymptomatic infections to fatal disease, having a great impact on cattle productions and causing substantial economic losses, mainly as a consequence of the occurrence of reproductive failures. The manuscript aims to provide an updated review of the currently available literature about the impact of HoBiPeV infection on cattle reproduction. The reproductive disorders observed in cattle due to natural and experimental infections caused by this virus are reported along with the few available in-vitro studies involving the reproductive tract. HoBiPeV should be considered among the bovine pathogens that impact on reproduction, but there is a need for more specific and sensitive diagnostic methods, while the cross-protection elicited by commercially available BVDV vaccines should be better investigated.

Veterinarians' Knowledge, Attitudes and Practices Associated with Bovine Viral Diarrhoea Virus Control and Prevention in South-East Australia

Simple Summary

Bovine Viral Diarrhoea Virus is a disease of cattle that causes production losses. Despite the virus being widespread across Australia, there are no government or industry-led programs to mitigate the impacts or eliminate Bovine Viral Diarrhoea Virus. Veterinarians were surveyed about their knowledge, attitudes and recommended practices regarding Bovine Viral Diarrhoea Virus and its control. We found that veterinarians’ knowledge of Bovine Viral Diarrhoea Virus in their region is limited, and their attitudes and recommendations for controlling the virus do not always align with those of producers. For example, veterinarians are concerned about the welfare and potential for disease spread associated with control measures involving persistently infected cattle, including a previously undocumented practice in which producers administer blood from persistently infected cattle into naïve cattle as a form of vaccination. This study highlights that a greater understanding of producers’ and veterinarians’ values is needed before Bovine Viral Diarrhoea Virus control could be implemented at a regional or country level.

Abstract

In Australia, the responsibility and associated costs for the control and prevention of Bovine Viral Diarrhoea Virus (BVDV) rest solely with producers. Veterinarians provide producers with farm-specific options for BVDV management and support BVDV control and elimination in their region. We surveyed veterinarians to determine their knowledge, attitudes and practices (KAP) associated with BVDV control in south-east Australia. We found that veterinarians’ recommendations do not always align with producers’ control measures. Veterinarians were uncertain about BVDV prevalence and the proportion of producers using BVDV control measures in their regions. Veterinarians generally promoted biosecurity and vaccination, and were concerned about the welfare and additional disease risks associated with persistently infected (PI) cattle. Veterinarians highlighted concerns about disease risks associated with a previously undocumented practice in which producers collect blood from PI cattle to administer to BVDV naïve cattle; termed “vampire vaccination” in this study. A greater understanding of the burden, impact and economics of BVDV is needed to align veterinarians’ and producers’ KAP to improve BVDV management on farms, and more appreciation of veterinarians’ and producers’ values is needed before BVDV control could be implemented at a regional or country level.

Diphtheric aspergillosis tracheitis with gastrointestinal dissemination secondary to viral infections in a dairy calf

Diphtheric aspergillosis tracheitis is an uncommon syndrome described in human pathology, usually associated with immunosuppression in the affected individuals. Interestingly, no comparative/equivalent cases were found in domestic animals. This report describes the pathological and mycological findings associated with diphtheric aspergillosis tracheitis in an immunocompromised calf. The main pathological findings were diphtheric tracheitis and rhinitis, and necrotizing ruminitis associated with intralesional septate, acute branching fungal hyphae consistent with Aspergillus spp. Mycological culture and isolation confirmed the fungal hyphae as A. fumigatus due to characteristic features. Immunohistochemistry (IHC) assays identified intralesional antigens of bovine viral diarrhea virus (BVDV) and malignant catarrhal fever virus (MCFV) at the trachea and small intestine; IHC detected intralesional antigens of bovine alphaherpesvirus 1 (BoHV-1) only at the trachea. These findings confirmed the simultaneous occurrence of A. fumigatus with concomitant infections due to BVDV, MCFV, and BoHV-1 in this calf. Since ovine gammaherpesvirus-2 (OvHV-2) is the cause of MCF in Brail, it is likely that the intralesional MCFV antigens identified were those of OvHV-2. In this case, disseminated aspergillosis was probably associated with the undeveloped immunological status of the calf that was further impaired due to the combined immunodepressive effects of BVDV and BoHV-1 infections. Although BVDV and BoHV-1 are infectious disease pathogens frequently associated with the development of bovine respiratory disease (BRD) in feedlot and dairy cattle, the identification of intralesional OvHV-2-like antigens in several parts of the lungs suggest that this MCFV also played a role in the BRD-associated lesions identified in this calf.

•

An unusual presentation of fungal diphtheric tracheitis associated with Aspergillus fumigatus is described in a dairy calf.

•

A Malignant Catarrhal Fever Virus, most likely, OvHV-2, was associated with the development of pneumonia in this calf.

•

Simultaneous infections in dairy calves may be more frequent than previously reported.

•

OvHV-2 should be considered as a possible disease pathogen associated with the development of bovine respiratory disease.

•

The immunodepressive effects of BVDV and BoHV-1 were fundamental for the development of the fungal disease observed in this calf.

Sequential exposure to bovine viral diarrhea virus and bovine coronavirus results in increased respiratory disease lesions: clinical, immunologic, pathologic, and immunohistochemical findings

Bovine coronaviruses (BoCVs) have been found in respiratory tissues in cattle and frequently associated with bovine respiratory disease (BRD); however, pathogenesis studies in calves are limited. To characterize the pathogenesis and pathogenicity of BoCV isolates, we used 5 different BoCV strains to inoculate colostrum-deprived calves, ~ 2-5 wk of age. Later, to determine if dual viral infection would potentiate pathogenicity of BoCV, calves were inoculated with BoCV alone, bovine viral diarrhea virus (BVDV) alone, or a series of dual-infection (BVDV-BoCV) schemes. A negative control group was included in all studies. Clinical signs and body temperature were monitored during the study and samples collected for lymphocyte counts, virus isolation, and serology. During autopsy, gross lesions were recorded and fixed tissues collected for histopathology and immunohistochemistry; fresh tissues were collected for virus isolation. Results suggest increased pathogenicity for isolate BoCV OK 1776. Increased body temperature was found in all virus-inoculated groups. Lung lesions were present in calves in all dual-infection groups; however, lesions were most pronounced in calves inoculated with BVDV followed by BoCV inoculation 6 d later. Lung lesions were consistent with mild-to-moderate interstitial pneumonia, and immunohistochemistry confirmed the presence of BoCV antigen. Our studies demonstrated that BVDV-BoCV dual infection may play an important role in BRD pathogenesis, and timing between infections seems critical to the severity of lesions.

Multi-pathogen serological survey of migratory caribou herds: A snapshot in time

Pathogens can impact host survival, fecundity, and population dynamics even when no obvious disease is observed. Few baseline data on pathogen prevalence and diversity of caribou are available, which hampers our ability to track changes over time and evaluate impacts on caribou health. Archived blood samples collected from ten migratory caribou herds in Canada and two in Greenland were used to test for exposure to pathogens that have the potential to effect population productivity, are zoonotic or are emerging. Relationships between seroprevalence and individual, population, and other health parameters were also examined. For adult caribou, the highest overall seroprevalence was for alphaherpesvirus (49%, n = 722), pestivirus (49%, n = 572) and Neospora caninum (27%, n = 452). Lower seroprevalence was found for parainfluenza virus type 3 (9%, n = 708), Brucella suis (2%, n = 758), and Toxoplasma gondii (2%, n = 706). No animal tested positive for antibodies against West Nile virus (n = 418) or bovine respiratory syncytial virus (n = 417). This extensive multi-pathogen survey of migratory caribou herds provides evidence that caribou are exposed to pathogens that may have impacts on herd health and revealed potential interactions between pathogens as well as geographical differences in pathogen exposure that could be linked to the bio-geographical history of caribou. Caribou are a keystone species and the socio-economic cornerstone of many indigenous cultures across the North. The results from this study highlight the urgent need for a better understanding of pathogen diversity and the impact of pathogens on caribou health.

Analysis of tRNA halves (tsRNAs) in serum from cattle challenged with bovine viral diarrhea virus

Acute infections of bovine viral diarrhea virus (BVDV) lead to a range of clinical presentations. Laboratory tests for detection depend on collection of samples during a short viremia. Acutely infected animals remain largely undiagnosed. Transfer RNA halves (tsRNAs) are hypothesized to function like microRNAs to regulate gene expression during an immune response. The objective of this study was to identify tsRNAs in cattle that had been challenged with a non-cytopathic field strain of BVDV. Colostrum-deprived neonatal Holstein calves were either challenged with BVDV (n=5) or mock challenged (n=4). Sera was collected prior to challenge and days 4, 9, and 16 post challenge. RNA was extracted and read counts of small non-coding RNAs were assessed using next-generation sequencing. A total of 87,838,207 reads identified 41 different tsRNAs. Two 5’ tsRNAs, tsRNA^ProAGG and tsRNA^ValAAC, differed across time. Two 5’ tsRNAs, tsRNA^GlyCCC and tsRNA^GlyGCC, differed between treatment groups across time. Four days post challenge, 5’ tsRNA^GlyCCC and tsRNA^GlyGCC were significantly lower in the challenged group than the control group. Further studies are needed to identify the importance and function of 5’ tsRNA^GlyCCC and tsRNA^GlyGCC in serum samples of cattle challenged with BVDV.

Mycoplasma bovis and viral agents associated with the development of bovine respiratory disease in adult dairy cows

The etiology and pathologic findings of bovine respiratory disease (BRD) in adult dairy cows (n = 35) from a commercial dairy herd in Southern Brazil were investigated. Pulmonary samples were examined for histopathologic patterns and specific features within these patterns, while immunohistochemical (IHC) assays were designed to detect the intralesional antigens of viral infectious disease agents and Mycoplasma bovis. Pneumonia was diagnosed in 91.4% (32/35) of these cases; neither pneumonia nor any of the infectious disease pathogens evaluated occurred in three cows. The presence of multiple respiratory pathogens in 75% (24/32) of these cases indicated the complex origin of pneumonia in cattle. Interstitial pneumonia, necrosuppurative bronchopneumonia and suppurative bronchopneumonia were the principal patterns of pulmonary disease identified by histopathology. The most frequent pathogens identified by IHC were bovine viral diarrhea virus (BVDV; n = 18), M. bovis (n = 16) and bovine alphaherpesvirus type 1 (BoHV-1; n = 14), followed by bovine respiratory syncytial virus (BRSV; n = 11) and bovine parainfluenza virus type 3 (BPIV-3; n = 5). Obliterative bronchiolitis and peribronchial lymphocytic cuffings were the characteristic histopathologic features associated with M. bovis. Necrohemorrhagic bronchitis with bronchial angiogenesis was associated with BoHV-1. Necrotizing bronchitis and bronchiolitis were associated with BVDV, BoHV-1 and BRSV. Ballooning degeneration of the bronchial and bronchiolar epithelia was associated with BRSV and BoHV-1. This is the first report from Brazil that correlated the histopathologic findings of BRD with the associated infectious disease agents by immunohistochemistry. M. bovis was frequently detected in the tissues of cows with fatal pulmonary disease during this study and may be a possible primary disease pathogen associated with the development of BRD in dairy cows. Additionally, the histopathologic features identified within patterns of pulmonary disease during this investigation may be an efficient diagnostic tool to associate histopathologic findings with specific agents of BRD in dairy cows.

Seroprevalence and risk factors associated with bovine viral diarrhea virus and bovine herpes virus-1 in Zanjan Province, Iran

Bovine viral diarrhea virus (BVDV) and bovine herpes virus-1 (BHV-1) remain as the major pathogens with heavy economic consequences in Iran. The prevalence of antibodies against BVDV and BHV-1, the rate of BVDV persistently infected (PI) animals, and associated risk factors were evaluated in a cross-sectional study carried out in Zanjan Province, Northwest Iran, in December 2011. A total number of 562 cattle in 10 herds and five cities were randomly selected, and their serum samples were tested to detect antibodies to these viruses and also BVDV antigen-positive (PI) animals. The data were analyzed with Pearson's correlation coefficient, chi-square, and logistic regression test. In total, nine and eight of the selected herds were seropositive to BVDV and BHV-1, respectively. The overall seroprevalence of these infections were estimated at 28.6 and 10.7% for BVDV and BHV-1, respectively, and 0.53% of the samples were detected as persistently infected. Statistical analysis revealed that sex, age, and farming system are risk factors for both infections (P < 0.05), while breed was determined as a strong risk factor only for BVDV (P < 0.001). In addition, the present study certainly identifies that infection with BVDV is associated with infection to BHV-1 (OR = 4.52, 95% CI: 2.60-7.80; P ˂ 0.001). The results add our knowledge about the prevalence and associated risk factors of BVDV and BHV-1 in Iran and imply that the prophylactic and surveillance strategies need to be implemented to reduce the risk of spread of these viruses.

A retrospective pathology study of two Neotropical deer species (1995-2015), Brazil: Marsh deer (Blastocerus dichotomus) and brown brocket deer (Mazama gouazoubira)

This retrospective study describes the biological and epidemiological aspects, gross and microscopical findings, and most likely causes of death (CD) in two species of Neotropical deer in Brazil. The animals were collected between 1995 and 2015 and represented 75 marsh deer (MD) and 136 brown brocket deer (BBD). Summarized, pneumonia was diagnosed microscopically in 48 MD and 52 BBD; 76 deer suffered trauma, involving dog attack (14 BBD) and vehicle-collision (14 BBD). Pulmonary edema (50 MD; 55 BBD) and congestion (57 MD; 78 BBD) were the most common findings for both species. Additionally, we diagnosed ruminal and myocardial mycosis in MD and BBD, respectively; ovarian dysgerminoma and pancreatic trematodiasis in BBD; and lesions suggestive of malignant catarrhal fever and orbiviral hemorrhagic disease in both species. The main CD in MD was: respiratory (41/75), alimentary, nutritional, trauma and euthanasia (3/75 each). Correspondingly, in BBD were: trauma (34/131), respiratory (30/131) and euthanasia (9/131). Respiratory disease was often defined by pulmonary edema and pneumonia. We provide evidence that respiratory disease, mainly pneumonia, is a critical pathological process in these Neotropical deer species. Although no etiological agents were identified, there is evidence of bacterial and viral involvement. Our results show trauma, mainly anthropogenic, as a common ailment in BBD. We propose to prioritize respiratory disease in future research focused on South American deer health aspects. We believe anthropogenic trauma may be a primary threat for populations of BBD.

Serological investigation of antibodies against respiratory viruses in calves from Brazilian family farming and their relation to clinical signs of bovine respiratory disease

ABSTRACT: Bovine respiratory disease (BRD) is responsible for economic losses in cattle production. Viruses are categorized as primary etiological agents. The aims of this study were to evaluate the presence of antibodies against bovine viral diarrhea virus (BVDV), bovine herpes virus type 1 (BoHV-1), and bovine respiratory syncytial virus (BRSV) in healthy and BRD calves from family farming in relation to clinical signs of BRD. Hundred and forty-five calves were randomly selected and physical examination was performed. Only 123 animals were classified as healthy and BRD calves. Antibodies were evaluated by virus neutralization test. Person’s Chi-square test and Fisher’s exact test were performed as univariate analysis. Binary Logistic Regression was applied as multivariate analysis. Variables with P<0.10 were considered statistically significant. Variables with 0.15<P<0.10 were considered as statistical tendencies. Antibodies against BoHV-1, BVDV, and BRSV were detected in 32%, 23% and 37% animals. Antibodies against both three viruses were detected in 26.8% of calves. The presence of antibodies against BRSV were associated to normal heart rates (P=0.018) and unilateral airflow (P=0.035). Tendency was observed to unilateral airflow (P=0.06) Statistical tendencies were observed to Ab-BoHV-1 and body temperature (P=0.119) and breathing pattern (P=0.123). The profile of antibodies against respiratory viruses in calves from Brazilian family farming was firstly described. The results confirmed the importance of some clinical signs to viral infection.

Establishment of a Bovine Viral Diarrhea Virus Type 2 Intranasal Challenge Model for Assessing Vaccine Efficacy

The objective of this study was to develop a bovine viral diarrhea virus type 2 (BVDV-2) challenge model suitable for evaluation of efficacy of BVDV vaccines; a model that mimics natural infection and induces clear leukopenia and viremia. Clinical, hematological and virological parameters were evaluated after infection of two age groups of calves (3 and 9 months) with two BVDV-2 strains (1362727 and 502643). Calves became pyrexic between 8 and 9 days post inoculation and exhibited symptoms, such as nasal discharge, mild depression, cough, and inappetence. Leukopenia with associated lymphopenia and neutropenia was evident in all groups with lowest leukocyte and lymphocyte counts reached 8 dpi and granulocyte counts between 11 and 16 dpi, dependent on the strain and age of the calves. A more severe thrombocytopenia was seen in those animals inoculated with strain 1362727. Leukocyte and nasal swab samples were positive by virus isolation, as early as 3 dpi and 2 dpi respectively, independent of the inocula used. All calves seroconverted with high levels of BVDV-2 neutralizing antibodies. BVDV RNA was evident as late as 90 dpi and provides the first evidence of the presence of replicating virus long after recovery from BVDV-2 experimental infection. In summary, moderate disease can be induced after experimental infection of calves with a low titer of virulent BVDV-2, with leukopenia, thrombocytopenia, viremia, and virus shedding. These strains represent an attractive model to assess the protective efficacy of existing and new vaccines against BVDV-2.

Molecular detection and characterization of transient bovine viral diarrhea virus (BVDV) infections in cattle commingled with ten BVDV persistently infected cattle

Fifty-three cattle of unknown serologic status that were not persistently infected (PI) with bovine viral diarrhea virus (BVDV) were commingled with 10 cattle that were PI with different strains of BVDV, and were monitored for an extended commingle period using a reverse-transcription real-time PCR (RT-rtPCR) BVDV assay on various sample types. Transient infections with BVDV were also assessed by virus isolation, virus neutralization (VN) assays, and direct buffy coat 5'-UTR sequencing. Infections were demonstrated in all cattle by RT-rtPCR; however, the detection rate was dependent on the type of sample. Buffy coat samples demonstrated a significantly greater number of positive results ( p ≤ 0.05) than either serum or nasal swab samples. Presence of elevated BVDV VN titers at the onset inversely correlated with the number of test days positive that an individual would be identified by RT-rtPCR from buffy coat samples, and directly correlated with the average Ct values accumulated over all RT-rtPCR test days from buffy coat samples. Both single and mixed genotype/subgenotype/strain infections were detected in individual cattle by direct sample 5'-UTR sequencing. A BVDV-2a strain from a PI animal was found to be the predominant strain infecting 64% of all non-PI cattle; BVDV-1b strains originating from 3 PI cattle were never detected in non-PI cattle. Although direct sample 5'-UTR sequencing was capable of demonstrating mixed BVDV infections, identifying all strains suspected was not always efficient or possible.

Vaccination of cattle against bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is responsible for significant losses to the cattle industry. Currently, modified-live viral (MLV) and inactivated viral vaccines are available against BVDV, often in combination with other viral and bacterial antigens. Inactivated and MLV vaccines provide cattle producers and veterinarians safe and efficacious options for herd immunization to limit disease associated with BVDV infection. Vaccination of young cattle against BVDV is motivated by prevention of clinical disease and limiting viral spread to susceptible animals. For reproductive-age cattle, vaccination to prevent viremia and birth of persistently infected offspring is considered more important, while also more difficult to achieve than prevention of clinical disease. Recent advances have been made in the understanding of BVDV vaccine efficacy. In terms of preventing clinical disease, current BVDV vaccines have been demonstrated to have a rapid onset of immunity and MLV vaccines can be effectively utilized in calves possessing maternal immunity. For reproductive protection, more recent studies using multivalent MLV vaccines have demonstrated consistent fetal protection rates in the range of 85-100% in experimental studies. Proper timing and administration of BVDV vaccines can be utilized to maximize vaccine efficacy to provide an important contribution to reducing risks associated with BVDV infection. With improvements in vaccine formulations and increased understanding of the protective immune response following vaccination, control of BVDV through vaccination can be enhanced.

Population-level effects of risk factors for bovine respiratory disease in Australian feedlot cattle

Results obtained from a nationwide longitudinal study were extended to estimate the population-level effects of selected risk factors on the incidence of bovine respiratory disease (BRD) during the first 50days at risk in medium-sized to large Australian feedlots. Population attributable fractions (PAF) and population attributable risks (PAR) were used to rank selected risk factors in order of importance from the perspective of the Australian feedlot industry within two mutually exclusive categories: 'intervention' risk factors had practical strategies that feedlot managers could implement to avoid exposure of cattle to adverse levels of the risk factor and a precise estimate of the population-level effect while 'others' did not. An alternative method was also used to quantify the expected effects of simultaneously preventing exposure to multiple management-related factors whilst not changing exposure to factors that were more difficult to modify. The most important 'intervention' risk factors were shared pen water (PAF: 0.70, 95% credible interval: 0.45-0.83), breed (PAF: 0.67, 95% credible interval: 0.54-0.77), the animal's prior lifetime history of mixing with cattle from other herds (PAF: 0.53, 95% credible interval: 0.30-0.69), timing of the animal's move to the vicinity of the feedlot (PAF: 0.45, 95% credible interval: 0.17-0.68), the presence of Bovine viral diarrhoea virus 1 (BVDV-1) in the animal's cohort (PAF: 0.30, 95% credible interval: 0.04-0.50), the number of study animals in the animal's group 13days before induction (PAF: 0.30, 95% credible interval: 0.10-0.44) and induction weight (PAF: 0.16, 95% credible interval: 0.09-0.23). Other important risk factors identified and prioritised for further research were feedlot region, season of induction and cohort formation patterns. An estimated 82% of BRD incidence was attributable to management-related risk factors, whereby the lowest risk category of a composite management-related variable comprised animals in the lowest risk category of at least four of the five component variables (shared pen water, mixing, move timing, BVDV-1 in the cohort and the number of animals in the animal's group-13). This indicated that widespread adoption of appropriate interventions including ensuring pen water is not shared between pens, optimising animal mixing before induction, timing of the animal's move to the vicinity of the feedlot, and group size prior to placing animals in feedlot pens, and avoiding BVDV-1 in cohorts could markedly reduce the incidence of BRD in medium-sized to large Australian feedlots.

An inactivated influenza D virus vaccine partially protects cattle from respiratory disease caused by homologous challenge

•

The emerging influenza D virus (IDV) caused respiratory disease in calves.

•

A homologous inactivated vaccine was immunogenic and partially protective.

•

IDV titers in vaccinated calves were significantly reduced compared to controls.

•

Fewer vaccinates were positive for IDV by immunohistochemistry.

•

These results demonstrate an etiologic role for IDV in bovine respiratory disease.

Originally isolated from swine, the proposed influenza D virus has since been shown to be common in cattle. Inoculation of IDV to naïve calves resulted in mild respiratory disease histologically characterized by tracheitis. As several studies have associated the presence of IDV with acute bovine respiratory disease (BRD), we sought to investigate the efficacy of an inactivated IDV vaccine. Vaccinated calves seroconverted with hemagglutination inhibition titers 137–169 following two doses. Non-vaccinated calves challenged with a homologous virus exhibited signs of mild respiratory disease from days four to ten post challenge which was significantly different than negative controls at days five and nine post challenge. Peak viral shedding of approximately 5 TCID₅₀/mL was measured in nasal and tracheal swabs and bronchoalveolar lavage fluids four to six days post challenge. Viral titers were significantly (P < 0.05) decreased 1.4 TCID₅₀/mL, 3.6 TCID₅₀/mL and 5.0 TCID₅₀/mL, respectively, in the aforementioned samples collected from vaccinated animals compared to non-vaccinated controls at peak shedding. Viral antigen was detected in the respiratory epithelium of the nasal turbinates and trachea by immunohistochemistry from all unvaccinated calves but in significantly fewer vaccinates. Inflammation characterized by neutrophils was observed in the nasal turbinate and trachea but not appreciably in lungs. Together these results support an etiologic role for IDV in BRD and demonstrate that partial protection is afforded by an inactivated vaccine.

Identification of Leukotoxin and other vaccine candidate proteins in a Mannheimia haemolytica commercial antigen

Bovine Respiratory Disease is the most costly disease that affects beef and dairy cattle industry. Its etiology is multifactorial, arising from predisposing environmental stress conditions as well as the action of several different respiratory pathogens. This situation has hindered the development of effective control strategies. Although different type of vaccines are available, many currently marketed vaccines are based on inactivated cultures of the main viral and bacterial agents involved in this pathology. The molecular composition of commercial veterinary vaccines is a critical issue. The present work aims to define at the proteomic level the most relevant valence of a line of commercial respiratory vaccines widely used in Central and South America. Since Mannheimia haemolytica is responsible for most of the disease associated morbid-mortality, we focused on the main proteins secreted by this pathogen, in particular Leukotoxin A, its main virulence factor. By Western blot analysis and mass spectrometry, Leukotoxin A was identified as a major component of M. haemolytica culture supernatants. We also identified other ten M. haemolytica proteins, including outer membrane proteins, periplasmic transmembrane solute transporters and iron binding proteins, which are relevant to achieve protective immunity against the pathogen. This work allowed a detailed molecular characterization of this vaccine component, providing evidence of its quality and efficacy. Furthermore, our results contributed to the identification of several proteins of interest as subunit vaccine candidates.

Bovine Viral Diarrhea Virus Type 2 Impairs Macrophage Responsiveness to Toll-Like Receptor Ligation with the Exception of Toll-Like Receptor 7

Bovine viral diarrhea virus (BVDV) is a member of the Flaviviridae family. BVDV isolates are classified into two biotypes based on the development of cytopathic (cp) or non-cytopathic (ncp) effects in epithelial cell culture. BVDV isolates are further separated into species, BVDV1 and 2, based on genetic differences. Symptoms of BVDV infection range from subclinical to severe, depending on strain virulence, and may involve multiple organ systems and induction of a generalized immunosuppression. During BVDV-induced immune suppression, macrophages, critical to innate immunity, may have altered pathogen recognition receptor (PRR) signaling, including signaling through toll-like receptors (TLRs). Comparison of BVDV 2 strains with different biotypes and virulence levels is valuable to determining if there are differences in host macrophage cellular responses between viral phenotypes. The current study demonstrates that cytopathic (cp), noncytopathic (ncp), high (hv) or low virulence (lv) BVDV2 infection of bovine monocyte-derived macrophages (MDMΦ) result in differential expression of pro-inflammatory cytokines compared to uninfected MDMΦ. A hallmark of cp BVDV2 infection is IL-6 production. In response to TLR2 or 4 ligation, as might be observed during secondary bacterial infection, cytokine secretion was markedly decreased in BVDV2-infected MDMΦ, compared to non-infected MDMΦ. Macrophages were hyporesponsive to viral TLR3 or TLR8 ligation. However, TLR7 stimulation of BVDV2-infected MDMΦ induced cytokine secretion, unlike results observed for other TLRs. Together, these data suggest that BVDV2 infection modulated mRNA responses and induced a suppression of proinflammatory cytokine protein responses to TLR ligation in MDMΦ with the exception of TLR7 ligation. It is likely that there are distinct differences in TLR pathways modulated following BVDV2 infection, which have implications for macrophage responses to secondary infections.

Type I and III IFNs Produced by Plasmacytoid Dendritic Cells in Response to a Member of the Flaviviridae Suppress Cellular Immune Responses

The pestivirus noncytopathic bovine viral diarrhea virus (BVDV) can suppress IFN production in the majority of cell types in vitro. However, IFN is detectable in serum during acute infection in vivo for ∼5-7 d, which correlates with a period of leucopoenia and immunosuppression. In this study, we demonstrate that a highly enriched population of bovine plasmacytoid dendritic cells (DCs) produced IFN in response to BVDV in vitro. We further show that the majority of the IFN produced in response to infection both in vitro and in vivo is type III IFN and acid labile. Further, we show IL-28B (IFN-λ3) mRNA is induced in this cell population in vitro. Supernatant from plasmacytoid DCs harvested postinfection with BVDV or recombinant bovine IFN-α or human IL-28B significantly reduced CD4(+) T cell proliferation induced by tubercle bacillus Ag 85-stimulated monocyte-derived DCs. Furthermore, these IFNs induced IFN-stimulated gene expression predominantly in monocyte-derived DCs. IFN-treated immature DCs derived from murine bone marrow also had a reduced capacity to stimulate T cell proliferative responses to tubercle bacillus Ag 85. Immature DCs derived from either source had a reduced capacity for Ag uptake following IFN treatment that is dose dependent. Immunosuppression is a feature of a number of pestivirus infections; our studies suggest type III IFN production plays a key role in the pathogenesis of this family of viruses. Overall, in a natural host, we have demonstrated a link between the induction of type I and III IFN after acute viral infection and transient immunosuppression.

Metagenomic characterization of the virome associated with bovine respiratory disease in feedlot cattle identified novel viruses and suggests an etiologic role for influenza D virus

Bovine respiratory disease (BRD) is the most costly disease affecting the cattle industry. The pathogenesis of BRD is complex and includes contributions from microbial pathogens as well as host, environmental and animal management factors. In this study, we utilized viral metagenomic sequencing to explore the virome of nasal swab samples obtained from feedlot cattle with acute BRD and asymptomatic pen-mates at six and four feedlots in Mexico and the USA, respectively, in April-October 2015. Twenty-one viruses were detected, with bovine rhinitis A (52.7 %) and B (23.7 %) virus, and bovine coronavirus (24.7 %) being the most commonly identified. The emerging influenza D virus (IDV) tended to be significantly associated (P=0.134; odds ratio=2.94) with disease, whereas viruses commonly associated with BRD such as bovine viral diarrhea virus, bovine herpesvirus 1, bovine respiratory syncytial virus and bovine parainfluenza 3 virus were detected less frequently. The detection of IDV was further confirmed using a real-time PCR assay. Nasal swabs from symptomatic animals had significantly more IDV RNA than those collected from healthy animals (P=0.04). In addition to known viruses, new genotypes of bovine rhinitis B virus and enterovirus E were identified and a newly proposed species of bocaparvovirus, Ungulate bocaparvovirus 6, was characterized. Ungulate tetraparvovirus 1 was also detected for the first time in North America to our knowledge. These results illustrate the complexity of the virome associated with BRD and highlight the need for further research into the contribution of other viruses to BRD pathogenesis.

Sensitivity and specificity of on-farm scoring systems and nasal culture to detect bovine respiratory disease complex in preweaned dairy calves

The California (CA) and Wisconsin (WI) clinical scoring systems have been proposed for bovine respiratory disease complex (BRDC) detection in preweaned dairy calves. The screening sensitivity (SSe), for estimating BRDC prevalence in a cohort of calves, diagnostic sensitivity (DSe), for confirming BRDC in ill calves, and specificity (Sp) were estimated for each of the scoring systems, as well as for nasal swab cultures for aerobic bacteria and mycoplasma species. Thoracic ultrasound and auscultation were used as the reference standard tests interpreted in parallel. A total of 536 calves (221 with BRDC and 315 healthy) were sampled from 5 premises in California. The SSe of 46.8%, DSe of 72.6%, and Sp of 87.4% was determined for the CA system. The SSe of 46.0%, DSe of 71.1%, and Sp of 91.2% was determined for the WI system. For aerobic culture, the SSe was 43.4%, DSe was 52.6%, and Sp was 71.3%; for Mycoplasma spp. culture, the SSe was 57.5%, DSe was 68.9%, and Sp was 59.7%. The screening and diagnostic sensitivities of the scoring systems were not significantly different but the Sp of the WI system was greater by 3.8%. Scoring systems can serve as rapid on-farm tools to determine the burden of BRDC in preweaned dairy calves. However, users may expect the SSe to be less than the DSe when confirming BRDC in an ill calf.

Single Pathogen Challenge with Agents of the Bovine Respiratory Disease Complex

Bovine respiratory disease complex (BRDC) is an important cause of mortality and morbidity in cattle; costing the dairy and beef industries millions of dollars annually, despite the use of vaccines and antibiotics. BRDC is caused by one or more of several viruses (bovine respiratory syncytial virus, bovine herpes type 1 also known as infectious bovine rhinotracheitis, and bovine viral diarrhea virus), which predispose animals to infection with one or more bacteria. These include: Pasteurella multocida, Mannheimia haemolytica, Mycoplasma bovis, and Histophilus somni. Some cattle appear to be more resistant to BRDC than others. We hypothesize that appropriate immune responses to these pathogens are subject to genetic control. To determine which genes are involved in the immune response to each of these pathogens it was first necessary to experimentally induce infection separately with each pathogen to document clinical and pathological responses in animals from which tissues were harvested for subsequent RNA sequencing. Herein these infections and animal responses are described.

Estimation of nasal shedding and seroprevalence of organisms known to be associated with bovine respiratory disease in Australian live export cattle

The prevalence of organisms known to be associated with bovine respiratory disease (BRD) was investigated in cattle prior to export. A quantitative reverse transcription polymerase chain reaction assay was used to detect nucleic acids from the following viruses and bacteria in nasal swab samples: Bovine coronavirus (BoCV; Betacoronavirus 1), Bovine herpesvirus 1 (BoHV-1), Bovine viral diarrhea virus 1 (BVDV-1), Bovine respiratory syncytial virus (BRSV), Bovine parainfluenza virus 3 (BPIV-3), Histophilus somni, Mycoplasma bovis, Mannheimia haemolytica, and Pasteurella multocida. Between 2010 and 2012, nasal swabs were collected from 1,484 apparently healthy cattle destined for export to the Middle East and Russian Federation. In addition, whole blood samples from 334 animals were tested for antibodies to BoHV-1, BRSV, BVDV-1, and BPIV-3 using enzyme-linked immunosorbent assay. The nasal prevalence of BoCV at the individual animal level was 40.1%. The nasal and seroprevalence of BoHV-1, BRSV, BVDV-1, and BPIV-3 was 1.0% and 39%, 1.2% and 46%, 3.0% and 56%, and 1.4% and 87%, respectively. The nasal prevalence of H. somni, M. bovis, M. haemolytica, and P. multocida was 42%, 4.8%, 13.4%, and 26%, respectively. Significant differences in nasal and seroprevalence were detected between groups of animals from different geographical locations. The results of the current study provide baseline data on the prevalence of organisms associated with BRD in Australian live export cattle in the preassembly period. This data could be used to develop strategies for BRD prevention and control prior to loading.

Immunopathologic Changes in the Thymus of Calves Pre-infected with BVDV and Challenged with BHV-1

The aim of this work was to investigate the effect of pre-infection with bovine viral diarrhoea virus (BVDV) on thymus immune cells from calves challenged with bovine herpesvirus 1 (BHV-1). Twelve Friesian calves, aged 8 to 9 months, were inoculated with non-cytopathic BVDV-1. Ten of them were subsequently challenged with BHV-1 and euthanized in batches of two at 1, 2, 4, 7 or 14 dpi with BHV-1. The other two calves were euthanized prior to the second inoculation and were used as BVDV-infected controls. A further 10 calves were inoculated solely with BHV-1 and euthanized at the same time points. Two calves were not inoculated with any agent and were used as negative controls. Quantitative changes in immune cells were evaluated with immunohistochemical methods to compare coinfected calves and calves challenged only with BHV-1. The results of this study pointed out BVDV as responsible for the thymic lesions observed in the experiment as well as for the majority of immunopathologic changes, including a downregulation of Foxp3 lymphocytes and TGFβ, which reverted as BVDV was cleared, and an overexpression of medullary CD8+ T cells. However, despite not inducing evident lesions in the thymus, BHV-1 seemed to prompt some immune alterations. Collectively, these data contribute to the knowledge on the immunopathologic alterations of the thymus during BVDV infections, and its importance in the development of secondary infections.

Development of a TaqMan assay for sensitive detection of all pestiviruses infecting cattle, including the emerging HoBi-like strains

A real-time RT-PCR assay based on the TaqMan technology was developed for rapid and sensitive detection of pestiviruses infecting cattle, i.e., bovine viral diarrhea virus (BVDV) 1, BVDV-2, and the emerging HoBi-like pestiviruses. The assay was linear and reproducible, being able to detect as few as 10 copies of viral RNA. By real-time RT-PCR analysis of 986 biological samples collected from cattle herd with clinical signs suggestive of pestivirus infection and from animals recruited in a pestivirus surveillance programme, 165 pestivirus positive samples were detected, including 6 specimens, 2 nasal swabs, and 4 EDTA-blood samples, that tested negative by a gel-based RT-PCR assay targeting the 5'UTR. The developed TaqMan assay represents a new reliable and effective tool for rapid and sensitive diagnosis of infections caused by all pestiviruses circulating in cattle, thus being useful for extensive surveillance programs in geographic areas where HoBi-like pestiviruses are co-circulating with BVDV-1 and BVDV-2.

Bovine Viral Diarrhea Virus-Associated Disease in Feedlot Cattle

Bovine viral diarrhea virus (BVDv) is associated with bovine respiratory disease complex and other diseases of feedlot cattle. Although occasionally a primary pathogen, BVDv's impact on cattle health is through the immunosuppressive effects of the virus and its synergism with other pathogens. The simple presence or absence of BVDv does not result in consistent health outcomes because BVDv is only one of many risk factors that contribute to disease syndromes. Current interventions have limitations and the optimum strategy for their uses to limit the health, production, and economic costs associated with BVDv have to be carefully considered for optimum cost-effectiveness.

Viral Dose and Immunosuppression Modulate the Progression of Acute BVDV-1 Infection in Calves: Evidence of Long Term Persistence after Intra-Nasal Infection

Bovine viral diarrhoea virus (BVDV) infection of cattle causes a diverse range of clinical outcomes from being asymptomatic, or a transient mild disease, to producing severe cases of acute disease leading to death. Four groups of calves were challenged with a type 1 BVDV strain, originating from a severe outbreak of BVDV in England, to study the effect of viral dose and immunosuppression on the viral replication and transmission of BVDV. Three groups received increasing amounts of virus: Group A received 10^2.55TCID₅₀/ml, group B 10^5.25TCID₅₀/ml and group C 10^6.7TCID ₅₀/ml. A fourth group (D) was inoculated with a medium dose (10^5.25TCID₅₀/ml) and concomitantly treated with dexamethasone (DMS) to assess the effects of chemically induced immunosuppression. Naïve calves were added as sentinel animals to assess virus transmission. The outcome of infection was dose dependent with animals given a higher dose developing severe disease and more pronounced viral replication. Despite virus being shed by the low-dose infection group, BVD was not transmitted to sentinel calves. Administration of dexamethasone (DMS) resulted in more severe clinical signs, prolonged viraemia and virus shedding. Using PCR techniques, viral RNA was detected in blood, several weeks after the limit of infectious virus recovery. Finally, a recently developed strand-specific RT-PCR detected negative strand viral RNA, indicative of actively replicating virus, in blood samples from convalescent animals, as late as 85 days post inoculation. This detection of long term replicating virus may indicate the way in which the virus persists and/or is reintroduced within herds.

The Molecular Biology of Pestiviruses

Pestiviruses are among the economically most important pathogens of livestock. The biology of these viruses is characterized by unique and interesting features that are both crucial for their success as pathogens and challenging from a scientific point of view. Elucidation of these features at the molecular level has made striking progress during recent years. The analyses revealed that major aspects of pestivirus biology show significant similarity to the biology of human hepatitis C virus (HCV). The detailed molecular analyses conducted for pestiviruses and HCV supported and complemented each other during the last three decades resulting in elucidation of the functions of viral proteins and RNA elements in replication and virus-host interaction. For pestiviruses, the analyses also helped to shed light on the molecular basis of persistent infection, a special strategy these viruses have evolved to be maintained within their host population. The results of these investigations are summarized in this chapter.

Review of BRD pathogenesis: the old and the new

The pathogenesis of bovine respiratory disease (BRD) is determined by a complex interaction of environmental, infectious, and host factors. Environment trends could impact feedlot cattle by increasing their level of stress. The polymicrobial nature of BRD produces synergies between infectious agents that can alter pathogenesis. However, the nature of the host response to these environmental and infectious challenges largely determines the characteristics of the progression and outcome of BRD.

The bovine viral diarrhea virus E2 protein formulated with a novel adjuvant induces strong, balanced immune responses and provides protection from viral challenge in cattle

Bovine viral diarrhea virus (BVDV) is still one of the most serious pathogens in cattle, meriting the development of improved vaccines. Recently, we developed a new adjuvant consisting of poly[di(sodium carboxylatoethylphenoxy)]-phosphazene (PCEP), either CpG ODN or poly(I:C), and an immune defense regulator (IDR) peptide. As this adjuvant has been shown to mediate the induction of robust, balanced immune responses, it was evaluated in an E2 subunit vaccine against BVDV in lambs and calves. The BVDV type 2 E2 protein was produced at high levels in a mammalian expression system and purified. When formulated with either CpG ODN or poly(I:C), together with IDR and PCEP, the E2 protein elicited high antibody titers and production of IFN-γ secreting cells in lambs. As the immune responses were stronger when poly(I:C) was used, the E2 protein with poly(I:C), IDR and PCEP was subsequently tested in cattle. Robust virus neutralizing antibodies as well as cell-mediated immune responses, including CD8(+) cytotoxic T cell (CTL) responses, were induced. The fact that CTL responses were demonstrated in calves vaccinated with an E2 protein subunit vaccine indicates that this adjuvant formulation promotes cross-presentation. Furthermore, upon challenge with a high dose of virulent BVDV-2, the vaccinated calves showed almost no temperature response, weight loss, leukopenia or virus replication, in contrast to the control animals, which had severe clinical disease. These data suggest that this E2 subunit formulation induces significant protection from BVDV-2 challenge, and thus is a promising BVDV vaccine candidate; in addition, the adjuvant platform has applications in bovine vaccines in general.

Patterns of detection of respiratory viruses in nasal swabs from calves in Ireland: a retrospective study

A retrospective analysis was conducted to investigate the prevalence and seasonality of bovine viral diarrhoea virus (BVDV), bovine coronavirus (BoCV), bovine herpesvirus-1 (BoHV-1), bovine respiratory syncytical virus (BRSV) and parainfluenza virus-3 (PI3V) in calves (aged three months and below) in Ireland. Results from real-time PCR testing, including cycle threshold values, conducted on nasal swabs (single or pooled) submitted from 1364 respiratory disease outbreaks between January 1, 2008 and December 31, 2012 were included in this study. One or more viruses were detected in 34.6 per cent of submissions, with BoCV detected most frequently (22.9 per cent), followed by BRSV (11.6 per cent), PI3 V (7.0 per cent), BoHV-1 (6.1 per cent) and BVDV (5.0 per cent). The detection rate of all viruses was higher when pooled multiple swabs were submitted from outbreaks rather than single swabs, with these differences being significant for all except BVDV. Two or more viruses were detected in 39.4 per cent of positive submissions, with BoCV and BRSV most commonly present as one of the two partners in detection. With the exception of BVDV, which was detected all year round, the others showed a clear seasonal pattern, being most commonly detected in winter and spring.

Development of a novel clinical scoring system for on-farm diagnosis of bovine respiratory disease in pre-weaned dairy calves

Several clinical scoring systems for diagnosis of bovine respiratory disease (BRD) in calves have been proposed. However, such systems were based on subjective judgment, rather than statistical methods, to weight scores. Data from a pair-matched case-control study on a California calf raising facility was used to develop three novel scoring systems to diagnose BRD in preweaned dairy calves. Disease status was assigned using both clinical signs and diagnostic test results for BRD-associated pathogens. Regression coefficients were used to weight score values. The systems presented use nasal and ocular discharge, rectal temperature, ear and head carriage, coughing, and respiratory quality as predictors. The systems developed in this research utilize fewer severity categories of clinical signs, require less calf handling, and had excellent agreement (Kappa > 0.8) when compared to an earlier scoring system. The first scoring system dichotomized all clinical predictors but required inducing a cough. The second scoring system removed induced cough as a clinical abnormality but required distinguishing between three levels of nasal discharge severity. The third system removed induced cough and forced a dichotomized variable for nasal discharge. The first system presented in this study used the following predictors and assigned values: coughing (induced or spontaneous coughing, 2 points), nasal discharge (any discharge, 3 points), ocular discharge (any discharge, 2 points), ear and head carriage (ear droop or head tilt, 5 points), fever (≥39.2°C or 102.5°F, 2 points), and respiratory quality (abnormal respiration, 2 points). Calves were categorized “BRD positive” if their total score was ≥4. This system correctly classified 95.4% cases and 88.6% controls. The second presented system categorized the predictors and assigned weights as follows: coughing (spontaneous only, 2 points), mild nasal discharge (unilateral, serous, or watery discharge, 3 points), moderate to severe nasal discharge (bilateral, cloudy, mucoid, mucopurlent, or copious discharge, 5 points), ocular discharge (any discharge, 1 point), ear and head carriage (ear droop or head tilt, 5 points), fever (≥39.2°C, 2 points), and respiratory quality (abnormal respiration, 2 points). Calves were categorized “BRD positive” if their total score was ≥4. This system correctly classified 89.3% cases and 92.8% controls. The third presented system used the following predictors and scores: coughing (spontaneous only, 2 points), nasal discharge (any, 4 points), ocular discharge (any, 2 points), ear and head carriage (ear droop or head tilt, 5 points), fever (≥39.2°C, 2 points), and respiratory quality (abnormal respiration, 2 points). Calves were categorized “BRD positive” if their total score was ≥5. This system correctly classified 89.4% cases and 90.8% controls. Each of the proposed systems offer few levels of clinical signs and data-based weights for on-farm diagnosis of BRD in dairy calves.