Mannheimia haemolytica and bovine respiratory disease

Antibiogram use on dairy cattle for bovine respiratory disease: Factors associated with bacterial pathogen identification and prediction of bacterial recovery using machine learning

Effective isolation of bacterial pathogens for bovine respiratory disease (BRD) is a critical step for accurate diagnosis of the agent associated with this disease on the dairy. Limited information is available on factors associated with herd-level bacterial pathogen recovery for BRD clinical cases, which are important data to help identify strategies to support the successful collection of a minimum number of each organism over time to generate cumulative antibiogram susceptibility testing reports. Our objective was to evaluate factors associated with the recovery of common pathobionts (Pasteurella multocida and Mannheimia haemolytica) in BRD clinical cases from preweaning calves, heifers, and cows at 3 California dairy farms over 2 yr. A second objective was to test the predictability of isolating these organisms in BRD clinical cases using the factors evaluated in the first objective utilizing machine learning (ML). During monthly herd visits, deep nasopharyngeal samples were collected from calves, heifers, and cows diagnosed with BRD over 2 yr. Samples were cultured in aerobic conditions, and pathogens were isolated through colony morphology and validated with MALDI-TOF MS. Evaluation of factors influencing bacterial recovery was initially tested for independence, followed by a logistic regression model and a stepwise logistic feature selection in SAS, and ML classifiers with leave-one-out cross-validation in Python packages. For our study, samples were collected from a total of 301 BRD clinical cases: 146 samples with a culture-positive for P. multocida, 63 samples with a culture-positive for M. haemolytica, and 3 samples with a culture-positive for Histophilus somni. For factors associated with the culture-positive of P. multocida in BRD clinical cases, an interaction between age and season was identified, where cows had overall lower odds of being culture-positive independently of the season when compared with calves in the spring and summer and heifers in the fall and winter. For factors associated with the culture-positive of M. haemolytica in BRD clinical cases, an interaction was also observed between age and season, but the farm further played a role in the odds of being culture-positive, with one farm having considerably greater odds than the remaining ones. Machine learning models with cross-validation showed a weak ability to distinguish positive from negative cases when using age, season, and farm for all scenarios according to F1-scores and receiver operating characteristic analysis. Differences in predictive abilities, factor importance, and the still limited number of predictors in these ML analyses further indicate a potential for building more robust future models once datasets are expanded and more robust algorithms are considered. Overall, correctly identifying factors that may be associated with the prevalence of BRD pathogens and, therefore, recovery of these pathogens is critical for the development of antibiogram programs for evaluation of the antimicrobial susceptibility of BRD pathogens.

A Systematic Study of Bovine Viral Diarrhoea Virus Co-Infection with Other Pathogens

Bovine viral diarrhoea virus (BVDV) is the causative agent of bovine viral diarrhoea/mucocutaneous disease (BVD-MD). Its associated co-infections pose a threat to the cattle industry, which is becoming a key breakthrough in the global system of prevention in the cattle industry. In recent years, cases of co-infection have occurred and been reported from time to time, and this situation not only poses certain difficulties in controlling the outbreak and in treatment in the farming industry, but also poses considerable challenges in detection and diagnosis. In this review, by systematically integrating studies on BVDV co-infection, we firstly compared and analysed the characteristics of BVDV co-infection with viruses, bacteria and other pathogens in in vivo/in vitro models in terms of synergism, host immune response and epidemiological transmission. Then we systematically constructed a BVDV Co-infection Impact Map, which demonstrates a paradigm of pathogen-host-immune interactions in the transmission of BVDV and provides a theoretical framework for breaking through the current precision diagnostic strategies and showcasing the effectiveness of integrated prevention and control.

Antibiogram use on dairy cattle for bovine respiratory disease: A repeated cross-sectional study evaluating antimicrobial susceptibility of Pasteurella multocida and Mannheimia haemolytica

Bovine respiratory disease (BRD) remains a costly challenge to the dairy industry, as the bacterial complex involved in BRD has shown decreased susceptibility to antimicrobials, exacerbating its effects on animal health, productivity, and recovery. In human medicine, cumulative antimicrobial susceptibility testing (CAST) is used to generate antibiograms that support empirical decision-making for antimicrobial treatment. The goal of this study was to evaluate a CAST framework for BRD in dairy cattle and factors of relevance when analyzing and reporting antibiogram data for on-farm treatment decisions. For this purpose, a repeated cross-sectional study was conducted using criteria adapted from the Clinical Laboratory Standards Institute for the collection, analysis, and presentation of CAST data. From 3 dairy farms in California, calves, heifers, and cows were sampled using deep nasopharyngeal swabs for culture and antimicrobial susceptibility testing for Pasteurella multocida and Mannheimia haemolytica. Antimicrobial susceptibility testing was performed using the minimum inhibitory concentration approach for 12 antimicrobial drugs of relevance to dairy cattle. The variability in the odds of nonsusceptible isolates was evaluated for effects of age group, farm, and season using a logistic regression model in SAS. The antimicrobial susceptibility of co-occurring P. multocida and M. haemolytica isolates were evaluated using Pearson chi-squared and Cohen's kappa in SAS. Overall, P. multocida isolates were mostly nonsusceptible to tetracycline (74%) and spectinomycin (46%), whereas M. haemolytica isolates were frequently nonsusceptible to penicillin (43%) and tetracycline (34%). There were increased odds of nonsusceptible isolates across farms and age groups, with calves and heifers showing a higher number of nonsusceptible isolates than cows. For P. multocida, isolates nonsusceptible to tetracycline and spectinomycin were affected by age group, with calves showing greater odds of nonsusceptibility to antimicrobials. The farm effect was significantly associated with P. multocida nonsusceptible to all antimicrobials but penicillin, suggesting individual farm management practices may heavily affect profiles of nonsusceptible BRD bacteria. Similarly, nonsusceptible M. haemolytica was consistently associated with farm for macrolides and tetracyclines and with age, with heifers showing the greatest odds of being nonsusceptible when compared with cows. Season did not affect the nonsusceptibility of either pathogen, suggesting that either California seasonal patterns or other factors, such as farm practices and animal management, play a more prominent role in the change of susceptibility profile. Overall, these findings highlight the potential effects of farm and age when interpreting data from CAST reports for BRD, where these and other factors should be considered when analyzing and presenting antibiogram reports.

Mannheimia haemolytica isogenic capsular and LPS-sialylation gene deletion mutants are attenuated in a calf lung challenge model

Bovine respiratory disease complex (BRDC) is a multifactorial syndrome that involves complex interactions between environment, bacterial/viral pathogens, and the host. Mannheimia haemolytica is the most significant bacterial pathogen associated with BRDC. This study investigated the virulence of a M. haemolytica serotype 1 capsular-deficient (Δcap) mutant and a M. haemolytica lipopolysaccharide (LPS)-sialylation-deficient (ΔneuA, cytidine monophosphate-sialic acid synthetase) mutant in a calf lung challenge model. Twelve colostrum-deprived calves were divided into three groups (four calves per group) and intratracheally administered inoculum of M. haemolytica wild-type (WT), M. haemolytica Δcap, or M. haemolytica ΔneuA strains (~5 × 108 CFU per animal). Animals were observed for signs of pneumonia and were humanely euthanized 2 to 3 days post-bacterial challenge. Lungs were examined for gross pulmonary lesions, histopathological changes, and bacterial culture. Calves administered WT M. haemolytica exhibited severe lung lesions characterized by extensive consolidation and hemorrhage. In contrast, calves administered M. haemolytica Δcap or M. haemolytica ΔneuA mutants displayed significantly reduced lung lesions (P < 0.05). The most severely affected lung lobes were the right cranial and right middle lobes, with ~50% consolidation. The WT group exhibited significantly higher lung tissue bacterial loads than either of the groups receiving the mutant strains (P < 0.05). The reduced clinical signs, pneumonic lung lesions, and bacterial recovery in the lungs of the calves challenged with either the Δcap or the ΔneuA M. haemolytica mutant strains indicated that these mutations were significantly less virulent than the parent strain.IMPORTANCEWhile Mannheimia haemolytica leukotoxin is well recognized as a major virulence factor, the roles of other possible virulence factors, such as capsule and sialic acid (sialylation of LPS) in M. haemolytica, have not been investigated in animal models. This study revealed that the abolishment of capsule (Δcap) or LPS sialylation (ΔneuA) significantly reduced the virulence of each mutant in calf lung challenges. These results demonstrate that both M. haemolytica capsule and sialylated LPS are important virulence factors that play a key role in the evasion of host defenses.

Comprehensive serotyping of Mannheimia haemolytica by a PCR system using the diversity of capsule biosynthesis genes

The bovine respiratory disease complex (BRDC) is a global issue affecting dairy and beef farms and is of major concern due to the high morbidity and mortality rates in calves, as well as decreased production it causes, resulting in significant economic losses. Mannheimia haemolytica is one of the secondary pathogens associated with BRDC. M. haemolytica is classified into 12 serotypes based on capsular antigens. In addition to the prevalent serotypes A1, A2, and A6, strains belonging to other serotypes also cause respiratory diseases in cattle and other ruminants, necessitating a method for their rapid and easy identification. In this study, we organized the capsule biosynthesis genes based on genome information from all serotype strains and designed 11 PCR primer pairs targeting serotype-specific genes, which could individually identify serotypes A14/A16, which possess homologous genes, as well as all other serotypes. Additionally, we developed two multiplex PCR kits that include these serotype-specific and M. haemolytica species-specific primers. Specificity testing using reference strains confirmed that these kits can simultaneously and clearly identify both the species and their serotypes. The PCR-based system described here could be a valuable tool for subtyping M. haemolytica strains in epidemiological studies and surveillance efforts in cattle and other reservoir animals. This study also carefully compared and discussed the differences between the capsule synthesis genes of A8 and A14 from previously published and those obtained in this study.

Nasal pathobiont abundance is a moderate feedlot-dependent indicator of bovine respiratory disease in beef cattle

BACKGROUND

Bovine respiratory disease (BRD) poses a persistent challenge in the beef cattle industry, impacting both animal health and economic aspects. Several risk factors make an animal susceptible to BRD, including bacteria such as Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis. Despite efforts to characterize and quantify these bacteria in the nasal cavity for disease diagnosis, more research is needed to understand if there is a pathobiont abundance threshold for clinical signs of respiratory disease, and if the results are similar across feedlots. This study aims to compare the nasal microbiome community diversity and composition, along with the abundance of four bacterial pathogens and associated serotypes, in apparently healthy and BRD-affected beef cattle. Nasal swabs were collected from four beef feedlots across the US, covering the years 2019 to 2022. The study included post-weaned beef cattle with diverse housing conditions.

RESULTS

Quantification of BRD-associated pathogens effectively distinguished BRD-affected from apparently healthy beef cattle, surpassing the efficacy of 16S rRNA gene sequencing of the nasal microbiome community. Specifically, H. somni, M. bovis, and M. haemolytica had higher abundance in the BRD-affected group. Utilizing the abundance of these pathobionts and analyzing their combined abundance with machine learning models resulted in an accuracy of approximately 63% for sample classification into disease status. Moreover, there were no significant differences in nasal microbiome diversity (alpha and beta) between BRD-affected and apparently healthy cattle; instead, differences were detected between feedlots.

CONCLUSIONS

Notably, this study sheds light on the beef cattle nasal microbiome community composition, revealing specific differences between BRD-affected and apparently healthy cattle. Pathobiont abundance was increased in some, but not all farms. Nonetheless, more research is needed to determine if these differences are consistent across other studies. Additionally, future research should consider bacterial-viral interactions in the beef nasal metagenome.

Impact of an Injectable Trace Mineral Supplement on the Immune Response and Outcome of Mannheimia haemolytica Infection in Feedlot Cattle

The study aimed to assess the impact of injectable trace mineral ("ITM"; Multimin90; Fort Collins, CO) supplementation on bacterial infection in cattle. Angus-crossbred steers (n = 32) were organized into two blocks by initial body weight. Steers were maintained on a ryelage and dry-rolled corn-based growing diet without supplementation of Zn, Cu, Mn, and Se for the duration of the study. The steers were transported 6 h, then randomized into three treatment groups: control received sterile saline ("CON"), ITM administered 1 day after transport (6 days before infection, "ITMPRE"), and ITM administered 2 days post infection (dpi) concurrent with antibiotic treatment ("ITMPOST"). Steers were infected with Mannheimia haemolytica on day 0, and all were treated with tulathromycin at 2 dpi. Plasma levels of Zn, Cu, and Se did not differ among treatments (P ≥ 0.74). Liver Se was higher in ITMPRE at 2 dpi (P < 0.05), and both ITM groups had higher liver Se at 5 dpi (P < 0.05) compared to CON. A time × treatment interaction was detected for liver Cu (P = 0.02). Clinical scores were lower (P < 0.05) in ITMPRE on 1 and 8 dpi and ITMPOST on 8 dpi compared to CON. Thoracic ultrasonography scores were lower in ITMPRE at 2 dpi compared to CON (P < 0.05) and ITMPOST (P < 0.1). No treatment effects (P > 0.10) were observed for bacterial detection from bronchoalveolar lavage (BAL) or nasopharyngeal swabs. At 5 dpi, both ITMPRE and ITMPOST showed higher frequencies of γδ T cells and NK cells in BAL compared to CON (P < 0.05). Before infection, leukocytes from ITMPRE steers produced more IL-6 (P < 0.01) in response to stimulation with the TLR agonist, Pam3CSK4. Use of ITM may be an effective strategy for improving disease resistance in feedlot cattle facing health challenges.

Gingivitis- and periodontitis-associated microbiota in bovine deciduous incisor teeth - A preliminary study

As ruminants are frequently affected by periodontal diseases, understanding their microbial communities is crucial. In this pilot study, we analyzed subgingival biofilm samples of young cattle across different states: clinically healthy (n = 5), gingivitis (n = 5), and periodontitis (n = 5) using 16S rRNA gene sequencing and co-occurrence network analysis. The findings revealed that Proteobacteria was the predominant phylum across all conditions, with Fusobacteriota constituting 27.6 % of the microbiota in periodontitis-affected sites. In healthy sites, Moraxella (21.11 %), Neisseria (13.16 %), and Lautropia (7.69 %) were the predominant genera; in gingivitis-affected sites, the leading genera were Neisseria (23.65 %), Moraxella (18.95 %), and Conchiformibius (10.79 %); and in periodontitis sites, Caviibacter (19.78 %), Moraxella (16.13 %), and Fusobacterium (7.56 %) were most prevalent. Richness and dissimilarity analyses did not show significant differences across the clinical states, but differences were found between gingivitis and periodontitis sites (p = 0.01) in diversity. The co-occurrence networks highlighted significant variances in the central phyla across the phenotypes, with a higher number of positive interactions observed in periodontitis-affected sites. Consequently, this study demonstrated that the microbiota associated with periodontitis in young cattle exhibits greater diversity compared to gingivitis. Notably, in the deciduous dentition of cattle, the genera Caviibacter and Moraxella are pivotal in the context of periodontitis and periodontal health, respectively.

Nasal pathobiont abundance does not differ between dairy cattle with or without clinical symptoms of bovine respiratory disease

BACKGROUND

Bovine respiratory disease (BRD) remains a significant health and economic problem to the dairy cattle industry. Multiple risk factors contribute to BRD susceptibility including the bacterial pathobionts Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis. Studies have characterized and quantified the abundance of these bacteria in the nasal cavity of cattle to infer and help disease diagnosis; nonetheless, there is still discrepancy in the results observed of when these microbes are commensal or pathogenic. Additionally, some of these studies are limited to a specific farm. The goal of this study is to compare the nasal microbiome community (diversity and composition) and the abundance of the four bacterial pathogens (by qPCR) in the nasal cavity to identify differences between dairy calves that are apparently healthy and those identified to have BRD. Nasal swabs were collected from approximately 50 apparently healthy and 50 BRD-affected calves sampled from five different dairy farms in the US (CA, IN, NY (two farms), and TX).

RESULTS

Calves diagnosed with BRD in NY, and TX had lower nasal microbiome diversity compared to the apparently healthy calves. Differences in the nasal microbiome composition were observed between the different farms predicted by Bray-Curtis and weighted UniFrac dissimilarities. Commensal and pathobiont genera Acinetobacter, Moraxella, Psychrobacter, Histophilus, Mannheimia, Mycoplasma, and Pasteurella were prevalent in the bovine nasal microbiome regardless of farm or disease status. The BRD-pathobiont H. somni was the most prevalent pathobiont among all the samples and M. bovis the least prevalent. Only in CA was the abundance of a pathobiont different according to disease status, where M. haemolytica was significantly more abundant in the BRD-affected animals than apparently healthy animals.

CONCLUSIONS

This study offers insight into the nasal microbiome community composition in both animals diagnosed with BRD and healthy animals, and shows that the farm effect plays a more significant role in determining the microbiome community than disease status in young dairy calves.

Glucocorticoid Receptor (GR) and Specificity Protein 1 (Sp1) or Sp3 Transactivate the Bovine Alphaherpesvirus 1 (BoHV-1)-Infected Cell Protein 0 Early Promoter

Bovine alphaherpesvirus 1 (BoHV-1) acute infection leads to latently infected sensory neurons in trigeminal ganglia. During lytic infection, the immediate early expression of infected cell protein 0 (bICP0) and bICP4 is regulated by an immediate early transcription unit 1 (IEtu1) promoter. A separate bICP0 early (E) promoter drives bICP0 as an early viral gene, presumably to sustain high levels during productive infection. Notably, bICP0 protein expression is detected before bICP4 during reactivation from latency, suggesting the bICP0 E promoter drives bICP0 protein expression during the early phases of reactivation from latency. The glucocorticoid receptor (GR) and Krüppel-like factor 4 (KLF4) cooperatively transactivate the bICP0 E promoter despite this promoter lacks a consensus GR response element (GRE). KLF and specificity protein (Sp) family members comprise a "super-family" of transcription factors. Consequently, we hypothesized Sp1 and Sp3 transactivated the bICP0 E promoter. These studies revealed GR and Sp3 or Sp1 cooperatively transactivated bICP0 E promoter activity. KLF4 and Sp3, but not Sp1, had an additive effect on bICP0 E promoter activity. Mutating the consensus Sp1 and CACCC binding sites proximal to the TATA box impaired promoter activity more than the Sp1 sites further upstream from the TATA box.

Prevalence of nasopharyngeal bacteria during naturally occurring bovine respiratory disease in commercial stocker cattle

Bovine respiratory disease (BRD) is one of the most common economic and health challenges to the beef cattle industry. Prophylactic use of antimicrobial drugs can alter the microbial communities in the respiratory tract. Considering that the bovine upper respiratory tract microbiome has been associated with generalized health, understanding the microenvironment that influences this microbiome may provide insights into the pathogenesis of BRD. This study aimed to determine temporal variation in nasopharyngeal (NP) microbiome in naturally occurring BRD in newly received stocker calves. Mixed breed steers (n = 40) were purchased from an auction market and housed in a commercial stocker farm. Clinical signs were used to identify BRD affected animals, and calves were categorized based on the number of treatments (NumTrt) received (0, 1, 2). On days 0, 7, 14, and 21, NP samples were collected, and subsequent DNA were isolated and sequenced. After sequencing, 16S rRNA V4 gene was amplified and utilized for NP bacterial determination. The difference in relative abundance based on day and NumTrt was measured using repeated measures ANOVA (PROC GLIMMIX; SAS 9.4). Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, and Verrucomicrobiota were the top phyla and Mycoplasma, Histophilus, Geobacillus, Saccharococcus, Lactobacillus, and Pasteurella were the top genera. In healthy calves, the relative abundance of Mycoplasma differed by day (P = 0.01), whereas on day 7, calves had five times greater abundance compared to day 0 (d 0: 0.06 ± 0.05; d 7: 0.30 ± 0.05). No differences were observed in the alpha diversity matrices based on day or NumTrt (P > 0.05). Results of this study suggest compositional variations in NP microbial populations occur during disease conditions.

The effects of simultaneous respiratory infections on the nasal shedding of Mycoplasmopsis bovirhinis in dairy calves

Although there are several studies that described the possible participation of Mycoplasmopsis bovirhinis (formerly, Mycoplasma bovirhinis) in respiratory disease in calves worldwide, none of these evaluated the effects of concomitant infections on the shedding of this organism. Accordingly, this study evaluated the effects of simultaneous respiratory infections in dairy calves on the nasal shedding of M. bovirhinis. A statistical two-step model, using univariable and multivariable with logistic regression was developed to investigate and predict the possible effects of simultaneous infections by Histophilus somni, Mannheimia haemolytica, Pasteurella multocida, bovine coronavirus (BCoV), and ovine gammaherpesvirus 2 (OvGHV2) in dairy calves on the nasal shedding of M. bovirhinis. The multivariable analysis demonstrated that dairy calves infected with OvGHV2 have 2.59 times likelihood of nasal shedding of M. bovirhinis relative to calves not infected by OvGHV2, while the odds of nasal shedding of M. bovirhinis was 3.46 times higher in dairy calves infected by M. haemolytica. In contrast, simultaneous respiratory infections in dairy calves by H. somni, P. multocida, and BCoV had no direct effect on the nasal shedding of M. bovirhinis. Consequently, infections by OvGHV2 and M. haemolytica may be possible risk factors for the nasal shedding of M. bovirhinis in dairy calves. These results demonstrated the importance of disease modeling in veterinary medicine to predict and understand the complex outcomes of associations in animals concomitantly infected by several disease pathogens.

Stress Can Induce Bovine Alpha-Herpesvirus 1 (BoHV-1) Reactivation from Latency

Bovine alpha-herpesvirus 1 (BoHV-1) is a significant problem for the cattle industry, in part because the virus establishes latency, and stressful stimuli increase the incidence of reactivation from latency. Sensory neurons in trigeminal ganglia and unknown cells in pharyngeal tonsils are importantsites for latency. Reactivation from latency can lead to reproductive problems in pregnant cows, virus transmission to young calves, suppression of immune responses, and bacterial pneumonia. BoHV-1 is also a significant cofactor in bovine respiratory disease (BRD). Stress, as mimicked by the synthetic corticosteroid dexamethasone, reproducibly initiates reactivation from latency. Stress-mediated activation of the glucocorticoid receptor (GR) stimulates viral replication and transactivation of viral promoters that drive the expression of infected cell protein 0 (bICP0) and bICP4. Notably, GR and Krüppel-like factor 15 (KLF15) form a feed-forward transcription loop that cooperatively transactivates immediate early transcription unit 1 (IEtu1 promoter). Two pioneer transcription factors, GR and KLF4, cooperatively transactivate the bICP0 early promoter. Pioneer transcription factors bind silent viral heterochromatin, remodel chromatin, and activate gene expression. Thus, wepredict that these novel transcription factors mediate early stages of BoHV-1 reactivation from latency.

The effect of methionine supplementation on receiving beef steers following a lipopolysaccharide challenge

The objective of this study was to evaluate the effects of methionine supplementation prior to and during a lipopolysaccharide (LPS) challenge on the performance and inflammatory biomarkers of receiving beef steers. Steers (n = 65; 295.8 ± 46.5 kg) were randomly assigned to 3 treatment groups: L0 = Control, receiving no supplement; L1 = 10 g/hd/d rumen-protected methionine (MetaSmart, Adisseo USA Inc., Alpharetta, GA); and L2 = 20 g/hd/d rumen-protected methionine and fed for 40 d at the West Texas A&M University Research Feedlot. On day 40, a subset of steers (n = 32; L0 = 10; L1 = 11; L2 = 11) were transported to the USDA Livestock Issues Research Unit, and on day 41 steers were weighed and fitted with indwelling rectal thermometers and jugular catheters. On day 42, steers were challenged i.v. with LPS (0.25 µg/kg BW). Blood samples were collected at -2, 0, 2, 4, 6, 8, 10, 12, 18, 24, 36, and 48 h relative to the LPS administration at 0 h. Serum was isolated to determine serum chemistry and inflammatory marker concentrations. Whole blood was used for hematology analysis. There were no differences in DMI or ADG (P ≥ 0.75) during 35 d of supplementation. A treatment × time interaction (P = 0.01) occurred for rectal temperature, where L2 steers had the greatest temperature following the challenge (P ≤ 0.05) compared to L1 and L0 steers. There was a treatment × time interaction (P = 0.03) for the change in white blood cells where L0 steers had the greatest change compared to L1 and L2 steers at various timepoints. There was a treatment × time interaction (P = 0.02) for the change in tumor necrosis factor-α concentration, where there was a greater increase in concentration in L0 compared to L1 and L2 steers. Additionally, there was a treatment × time interaction (P < 0.01) for Macrophage Inflammatory Protein-1β (MIP-1β) concentrations, where concentrations were greater in L0 compared with L1 and L2 steers from 2 to 4 h post-challenge. There was a treatment × time interaction for plasma total protein concentration (P < 0.01) where L0 steers had less plasma total protein compared with L1 and L2 steers, while L1 steers had less plasma total protein than L2 steers at -2 h prior to LPS challenge. These data suggest that methionine supplementation may have an immunomodulatory effect in beef steers that may improve response to pathogens.

Identification of DNA methylation markers for age and Bovine Respiratory Disease in dairy cattle: A pilot study based on Reduced Representation Bisulfite Sequencing

Methylation profiles of animals are known to differ by age and disease status. Bovine respiratory disease (BRD), a complex infectious disease, primarily affects calves and has significant impact on animal welfare and the cattle industry, due to production losses, increased veterinary costs as well as animal losses. BRD susceptibility is multifactorial, influenced by both environmental and genetic factors. We have performed a pilot study to investigate the epigenetic profile of BRD susceptibility in six calves (three healthy versus three diagnosed with BRD) and age-related methylation differences between healthy calves and adult dairy cows (three calves versus four adult cows) using Reduced Representation Bisulfite Sequencing (RRBS). We identified 2537 genes within differentially methylated regions between calves and adults. Functional analysis revealed enrichment of developmental pathways including cell fate commitment and tissue morphogenesis. Between healthy and BRD affected calves, 964 genes were identified within differentially methylated regions. Immune and vasculature regulatory pathways were enriched and key candidates in BRD susceptibility involved in complement cascade regulation, vasoconstriction and respiratory cilia structure and function were identified. Further studies with a greater sample size are needed to validate these findings and formulate integration into breeding programmes aiming to increase animal longevity and disease resistance.

Association of clinical respiratory disease signs and lower respiratory tract bacterial pathogens with systemic inflammatory response in preweaning dairy calves

This study investigated the potential associations between 3 acute phase proteins (APP)-haptoglobin, serum amyloid A-and fibrinogen, clinical signs of respiratory disease, and the presence of bacterial pathogens in the lower respiratory tract (LRT) of preweaning dairy calves. This cross-sectional study included 150 preweaning calves (2-86 d old) from 15 large dairy herds in Estonia. Tracheobronchial lavage, blood, and fecal samples were collected from 5 calves showing clinical signs indicative of LRT disease, and samples from 5 calves without clinical signs of LRT disease per herd. All samples collected from these calves were analyzed for concentrations of systemic APP, LRT bacteria, and intestinal pathogens. Heifer blood and bulk tank milk samples were collected for the detection of disease-specific antibodies against bovine herpesvirus 1, bovine viral diarrhea virus, bovine respiratory syncytial virus, and Mycoplasma bovis. Mixed-effects linear regression models were used to analyze the associations of clinical respiratory disease signs and LRT bacteria with APP. Increased plasma fibrinogen concentrations in calves were associated with higher rectal temperature (>39.5°C), increased respiratory rate (>50 breaths/min), and coughing. Increased serum amyloid A concentrations were associated with higher rectal temperature (>39.5°C) and respiratory rate between 40 and 50 breaths/min. Calves with the presence of fecal Cryptosporidium spp. and rectal temperature of 39°C and above had increased serum haptoglobin concentrations. Increased fibrinogen concentrations were associated with the presence of Pasteurella multocida in the calf LRT, whereas increased concentrations of fibrinogen and serum amyloid A were associated with the presence of Trueperella pyogenes. In conclusion, APP showed variable associations with clinical signs of respiratory disease and LRT bacteria. Plasma fibrinogen concentration could be used as a complementary calf-side test to assess systemic inflammation caused by LRT bacteria such as Pasteurella multocida and Trueperella pyogenes in preweaning dairy calves.

Apo-Lactoferrin Inhibits the Proteolytic Activity of the 110 kDa Zn Metalloprotease Produced by Mannheimia haemolytica A2

Mannheimia haemolytica is the main etiological bacterial agent in ruminant respiratory disease. M. haemolytica secretes leukotoxin, lipopolysaccharides, and proteases, which may be targeted to treat infections. We recently reported the purification and in vivo detection of a 110 kDa Zn metalloprotease with collagenase activity (110-Mh metalloprotease) in a sheep with mannheimiosis, and this protease may be an important virulence factor. Due to the increase in the number of multidrug-resistant strains of M. haemolytica, new alternatives to antibiotics are being explored; one option is lactoferrin (Lf), which is a multifunctional iron-binding glycoprotein from the innate immune system of mammals. Bovine apo-lactoferrin (apo-bLf) possesses many properties, and its bactericidal and bacteriostatic effects have been highlighted. The present study was conducted to investigate whether apo-bLf inhibits the secretion and proteolytic activity of the 110-Mh metalloprotease. This enzyme was purified and sublethal doses of apo-bLf were added to cultures of M. haemolytica or co-incubated with the 110-Mh metalloprotease. The collagenase activity was evaluated using zymography and azocoll assays. Our results showed that apo-bLf inhibited the secretion and activity of the 110-Mh metalloprotease. Molecular docking and overlay assays showed that apo-bLf bound near the active site of the 110-Mh metalloprotease, which affected its enzymatic activity.

Identification of genetic markers of resistance to macrolide class antibiotics in Mannheimia haemolytica isolates from a Saskatchewan feedlot

Mannheimia haemolytica is a major contributor to bovine respiratory disease (BRD), which causes substantial economic losses to the beef industry, and there is an urgent need for rapid and accurate diagnostic tests to provide evidence for treatment decisions and support antimicrobial stewardship. Diagnostic sequencing can provide information about antimicrobial resistance genes in M. haemolytica more rapidly than conventional diagnostics. Realizing the full potential of diagnostic sequencing requires a comprehensive understanding of the genetic markers of antimicrobial resistance. We identified genetic markers of resistance in M. haemolytica to macrolide class antibiotics commonly used for control of BRD. Genome sequences were determined for 99 M. haemolytica isolates with six different susceptibility phenotypes collected over 2 years from a feedlot in Saskatchewan, Canada. Known macrolide resistance genes estT, msr(E), and mph(E) were identified in most resistant isolates within predicted integrative and conjugative elements (ICEs). ICE sequences lacking antibiotic resistance genes were detected in 10 of 47 susceptible isolates. No resistance-associated polymorphisms were detected in ribosomal RNA genes, although previously unreported mutations in the L22 and L23 ribosomal proteins were identified in 12 and 27 resistant isolates, respectively. Pangenome analysis led to the identification of 79 genes associated with resistance to gamithromycin, of which 95% (75 of 79) had no functional annotation. Most of the observed phenotypic resistance was explained by previously identified antibiotic resistance genes, although resistance to the macrolides gamithromycin and tulathromycin was not explained in 39 of 47 isolates, demonstrating the need for continued surveillance for novel determinants of macrolide resistance.IMPORTANCEBovine respiratory disease is the costliest disease of beef cattle in North America and the most common reason for injectable antibiotic use in beef cattle. Metagenomic sequencing offers the potential to make economically significant reductions in turnaround time for diagnostic information for evidence-based selection of antibiotics for use in the feedlot. The success of diagnostic sequencing depends on a comprehensive catalog of antimicrobial resistance genes and other genome features associated with reduced susceptibility. We analyzed the genome sequences of isolates of Mannheimia haemolytica, a major bovine respiratory disease pathogen, and identified both previously known and novel genes associated with reduced susceptibility to macrolide class antimicrobials. These findings reinforce the need for ongoing surveillance for markers of antimicrobial resistance to support improved diagnostics and antimicrobial stewardship.

The respiratory and fecal microbiota of beef calves from birth to weaning

The development and growth of animals coincide with the establishment and maturation of their microbiotas. To evaluate the respiratory and fecal microbiotas of beef calves from birth to weaning, a total of 30 pregnant cows, and their calves at birth, were enrolled in this study. Deep nasal swabs and feces were collected from calves longitudinally, starting on the day of birth and ending on the day of weaning. Nasopharyngeal, vaginal, and fecal samples were also collected from cows, and the microbiotas of all samples were analyzed. The fecal microbiota of calves was enriched with Lactobacillus during the first 8 weeks of life, before being displaced by genera associated with fiber digestion, and then increasing in diversity across time. In contrast, the diversity of calf respiratory microbiota generally decreased with age. At birth, the calf and cow nasal microbiotas were highly similar, indicating colonization from dam contact. This was supported by microbial source-tracking analysis. The structure of the calf nasal microbiota remained similar to that of the cows, until weaning, when it diverged. The changes were driven by a decrease in Lactobacillus and an increase in genera typically associated with bovine respiratory disease, including Mannheimia, Pasteurella, and Mycoplasma. These three genera colonized calves early in life, though Mannheimia was initially transferred from the cow reproductive tract. Path analysis was used to model the interrelationships of calf respiratory and fecal microbiotas. It was observed that respiratory Lactobacillus and fecal Oscillospiraceae UCG-005 negatively affected the abundance of Mannheimia or Pasteurella.IMPORTANCEIn beef cattle production, bovine respiratory disease (BRD) accounts for most of the feedlot morbidities and mortalities. Metaphylaxis is a common management tool to mitigate BRD, however its use has led to increased antimicrobial resistance. Novel methods to mitigate BRD are needed, including microbiota-based strategies. However, information on the respiratory bacteria of beef calves prior to weaning was limited. In this study, it was shown that the microbiota of cows influenced the initial composition of both respiratory and fecal microbiotas in calves. While colonization of the respiratory tract of calves by BRD-associated genera occurred early in life, their relative abundances increased at weaning, and were negatively correlated with respiratory and gut bacteria. Thus, microbiotas of both the respiratory and gastrointestinal tracts have important roles in antagonism of respiratory pathogens and are potential targets for enhancing calf respiratory health. Modulation may be most beneficial, if done prior to weaning, before opportunistic pathogens establish colonization.

Mucosal Immunization with Spore-Based Vaccines against Mannheimia haemolytica Enhances Antigen-Specific Immunity

BACKGROUND

Mannheimia haemolytica is a bovine respiratory pathogen commonly associated with bacterial bronchopneumonia. Current vaccine strategies have shown variable efficacy in feedlot cattle, and therefore novel vaccines are needed. Bacillus subtilis spores have been investigated as a mucosal vaccine platform, due to their ability to bind and present antigens to the mucosa and act as an adjuvant. The aim of this study was to develop two spore-based mucosal vaccines targeting M. haemolytica and evaluate their immunogenicity in mice.

METHODS

Two antigen constructs composed of cholera toxin B subunit, M. haemolytica leukotoxin, and either the M. haemolytica outer membrane protein PlpE (MhCP1) or GS60 (MhCP2) were synthesized, purified and then bound to spores as vaccines. In two separate mice trials, the spore-bound vaccines (Spore-MhCP1 and Spore-MhCP2) were administered to mice through intranasal and intragastric routes, while free antigens were administered intranasally and intramuscularly. Unbound spores were also evaluated intranasally. Antigen-specific serum IgG and mucosal IgA from bronchoalveolar lavage, feces, and saliva were measured after vaccination. Mice sera from all treatment groups were assessed for their bactericidal activity against M. haemolytica.

RESULTS

In both mice experiments, intramuscular immunization induced the strongest serum IgG antibody response. However, the intranasal administration of Spore-MhCP1 and Spore-MhCP2 elicited the greatest secretory IgA-specific response against leukotoxin, PlpE, and GS60 in bronchoalveolar lavage, saliva, and feces (p < 0.05). Compared to the intranasal administration of free antigen, spore-bound antigen groups showed greater bactericidal activity against M. haemolytica (p < 0.05).

CONCLUSIONS

Since intranasally delivered Spore-MhCP1 and Spore-MhCP2 elicited both systemic and mucosal immune responses in mice, these vaccines may have potential to mitigate lung infection in cattle by restricting M. haemolytica colonization and proliferation in the respiratory tract. The efficacy of these mucosal spore-based vaccines merits further assessment against M. haemolytica in cattle.

Transcriptomic profiles of Mannheimia haemolytica planktonic and biofilm associated cells

Mannheimia haemolytica is the principal agent contributing to bovine respiratory disease and can form biofilms with increased resistance to antibiotic treatment and host immune defenses. To investigate the molecular mechanisms underlying M. haemolytica biofilm formation, transcriptomic analyses were performed with mRNAs sequenced from planktonic and biofilm cultures of pathogenic serotypes 1 (St 1; strain D153) and St 6 (strain D174), and St 2 (strain D35). The three M. haemolytica serotypes were cultured in two different media, Roswell Park Memorial Institute (RPMI) 1640 and brain heart infusion (BHI) to form the biofilms. Transcriptomic analyses revealed that the functions of the differentially expressed genes (DEGs) in biofilm associated cells were not significantly affected by the two media. A total of 476 to 662 DEGs were identified between biofilm associated cells and planktonic cells cultured under BHI medium. Functional analysis of the DEGs indicated that those genes were significantly enriched in translation and many biosynthetic processes. There were 234 DEGs identified in St 1 and 6, but not in St 2. The functions of the DEGs included structural constituents of ribosomes, transmembrane proton transportation, proton channels, and proton-transporting ATP synthase. Potentially, some of the DEGs identified in this study provide insight into the design of new M. haemolytica vaccine candidates.

Molecular identification and characterisation of Mannheimia haemolytica

Mannheimia haemolytica is known as one of the major bacterial contributors to Bovine Respiratory Disease (BRD) syndrome. This study sought to establish a novel species-specific PCR to aid in identification of this key pathogen. As well, an existing multiplex PCR was used to determine the prevalence of serovars 1, 2 or 6 in Australia. Most of the 65 studied isolates originated from cattle with a total of 11 isolates from small ruminants. All problematic field isolates in the identification or serotyping PCRs were subjected to whole genome sequencing and bioinformatic analysis. The field isolates were also subjected to rep-PCR fingerprinting. A total of 59 out of the 65 tested isolates were conformed as M. haemolytica by the new species-specific PCR which is based on the rpoB gene. The confirmed M. haemolytica field isolates were assigned to serovars 1 (24 isolates), 2 (seven isolates) and 6 (26 isolates) while two of the isolates were negative in the serotyping PCR. The two non-typeable isolates were assigned to serovar 7 and 14 following whole genome sequencing and bioinformatic analysis. The rep-PCR typing resulted in five major clusters with serovars 1 and 6 often within the same cluster. The M. haemolytica-specific PCR developed in this work was species specific and should be a valuable support for frontline diagnostic laboratories. The serotyping results support the relative importance of serovars 1 and 6 in bovine respiratory disease.

Enhanced phagocytosis and complement-mediated killing of Mannheimia haemolytica serotype 1 following in-frame CMP-sialic acid synthetase (neuA) gene deletion

IMPORTANCE

The Gram-negative coccobacillus Mannheimia haemolytica is a natural inhabitant of the upper respiratory tract in ruminants and the most common bacterial agent involved in bovine respiratory disease complex development. Key virulence factors harbored by M. haemolytica are leukotoxin, lipopolysaccharide, capsule, adhesins, and neuraminidase which are involved in evading innate and adaptive immune responses. In this study, we have shown that CMP-sialic acid synthetase (neuA) is necessary for the incorporation of sialic acid onto the membrane, and inactivation of neuA results in increased phagocytosis and complement-mediated killing of M. haemolytica, thus demonstrating that sialylation contributes to the virulence of M. haemolytica.

Auction market placement and a rest stop during transportation affect the respiratory bacterial microbiota of beef cattle

Background

Bovine respiratory disease (BRD) is a significant health problem in beef cattle production, resulting in considerable economic losses due to mortalities, cost of treatment, and reduced feed efficiency. The onset of BRD is multifactorial, with numerous stressors being implicated, including transportation from farms to feedlots. In relation to animal welfare, regulations or practices may require mandatory rest times during transportation. Despite this, there is limited information on how transportation and rest stops affect the respiratory microbiota.

Results

This study evaluated the effect of cattle source (ranch-direct or auction market-derived) and rest stop duration (0 or 8 h of rest) on the upper respiratory tract microbiota and its relationship to stress response indicators (blood cortisol and haptoglobin) of recently weaned cattle transported for 36 h. The community structure of bacteria was altered by feedlot placement. When cattle were off-loaded for a rest, several key bacterial genera associated with BRD (Mannheimia, Histophilus, Pasteurella) were increased for most sampling times after feedlot placement for the ranch-direct cattle group, compared to animals given no rest stop. Similarly, more sampling time points had elevated levels of BRD-associated genera when auction market cattle were compared to ranch-direct. When evaluated across time and treatments several genera including Mannheimia, Moraxella, Streptococcus and Corynebacterium were positively correlated with blood cortisol concentrations.

Conclusion

This is the first study to assess the effect of rest during transportation and cattle source on the respiratory microbiota in weaned beef calves. The results suggest that rest stops and auction market placement may be risk factors for BRD, based solely on increased abundance of BRD-associated genera in the upper respiratory tract. However, it was not possible to link these microbiota to disease outcome, due to low incidence of BRD in the study populations. Larger scale studies are needed to further define how transportation variables impact cattle health.

Complete genome sequence of Mannheimia bovis isolated from a healthy feedlot calf in Saskatchewan, Canada

A lack of whole genome sequences for Mannheimia spp. other than Mannheimia haemolytica complicates their identification. Here, we present the genome sequence of Mannheimia bovis 39324.S-11, isolated from a healthy calf on a feedlot in Saskatchewan, Canada, and compare it to ZY190616T, which is currently the only other isolate of M. bovis for which sequence is publicly available.

Development of a plant-based oral vaccine candidate against the bovine respiratory pathogen Mannheimia haemolytica

Bovine respiratory disease (BRD) affects feedlot cattle across North America, resulting in economic losses due to animal treatment and reduced performance. In an effort to develop a vaccine candidate targeting a primary bacterial agent contributing to BRD, we produced a tripartite antigen consisting of segments of the virulence factor Leukotoxin A (LktA) and lipoprotein PlpE from Mannheimia haemolytica, fused to a cholera toxin mucosal adjuvant (CTB). This recombinant subunit vaccine candidate was expressed in the leaves of Nicotiana benthamiana plants, with accumulation tested in five subcellular compartments. The recombinant protein was found to accumulate highest in the endoplasmic reticulum, but targeting to the chloroplast was employed for scaling up production due the absence of post-translational modification while still producing feasible levels. Leaves were freeze dried, then orally administered to mice to determine its immunogenicity. Sera from mice immunized with leaf tissue expressing the recombinant antigen contained IgG antibodies, specifically recognizing both LktA and PlpE. These mice also had a mucosal immune response to the CTB+LktA+PlpE protein as measured by the presence of LktA- and PlpE-specific IgA antibodies in lung and fecal material. Moreover, the antigen remained stable at room temperature with limited deterioration for up to one year when stored as lyophilized plant material. This study demonstrated that a recombinant antigen expressed in plant tissue elicited both humoral and mucosal immune responses when fed to mice, and warrants evaluation in cattle.

Development of a spore-based mucosal vaccine against the bovine respiratory pathogen Mannheimia haemolytica

Bovine respiratory disease (BRD) is a significant health issue in the North American feedlot industry, causing substantial financial losses due to morbidity and mortality. A lack of effective vaccines against BRD pathogens has resulted in antibiotics primarily being used for BRD prevention. The aim of this study was to develop a mucosal vaccine against the BRD pathogen, Mannheimia haemolytica, using Bacillus subtilis spores as an adjuvant. A chimeric protein (MhCP) containing a tandem repeat of neutralizing epitopes from M. haemolytica leukotoxin A (NLKT) and outer membrane protein PlpE was expressed to produce antigen for adsorption to B. subtilis spores. Adsorption was optimized by comparing varying amounts of antigen and spores, as well as different buffer pH and reaction temperatures. Using the optimal adsorption parameters, spore-bound antigen (Spore-MhCP) was prepared and administered to mice via two mucosal routes (intranasal and intragastric), while intramuscular administration of free MhCP and unvaccinated mice were used as positive and negative control treatments, respectively. Intramuscular administration of MhCP elicited the strongest serum IgG response. However, intranasal immunization of Spore-MhCP generated the best secretory IgA-specific response against both PlpE and NLKT in all samples evaluated (bronchoalveolar lavage, saliva, and feces). Since proliferation of M. haemolytica in the respiratory tract is a prerequisite to lung infection, this spore-based vaccine may offer protection in cattle by limiting colonization and subsequent infection, and Spore-MhCP warrants further evaluation in cattle as a mucosal vaccine against M. haemolytica.

The bovine nasal fungal community and associations with bovine respiratory disease

Introduction

Effective identification and treatment of bovine respiratory disease (BRD) is an ongoing health and economic issue for the dairy and beef cattle industries. Bacteria pathogens Pasteurellamultocida, Mycoplasmabovis, Mannheimia haemolytica, and Histophilus somni and the virus Bovine herpesvirus-1 (BHV-1), Bovine parainfluenza-3 virus (BPIV-3), Bovine respiratory syncytial virus (BRSV), Bovine adenovirus 3 (BAdV3), bovine coronavirus (BoCV) and Bovine viral diarrhea virus (BVDV) have commonly been identified in BRD cattle; however, no studies have investigated the fungal community and how it may also relate to BRD.

Methods

The objective of this study was to understand if the nasal mycobiome differs between a BRD-affected (n = 56) and visually healthy (n = 73) Holstein steers. Fungal nasal community was determined by using Internal Transcribed Spacer (ITS) sequencing.

Results

The phyla, Ascomycota and Basidiomycota, and the genera, Trichosporon and Issatchenkia, were the most abundant among all animals, regardless of health status. We identified differences between healthy and BRD animals in abundance of Trichosporon and Issatchenkia orientalis at a sub-species level that could be a potential indicator of BRD. No differences were observed in the nasal fungal alpha and beta diversity between BRD and healthy animals. However, the fungal community structure was affected based on season, specifically when comparing samples collected in the summer to the winter season. We then performed a random forest model, based on the fungal community and abundance of the BRD-pathobionts (qPCR data generated from a previous study using the same animals), to classify healthy and BRD animals and determine the agreement with visual diagnosis. Classification of BRD or healthy animals using ITS sequencing was low and agreed with the visual diagnosis with an accuracy of 51.9%. A portion of the ITS-predicted BRD animals were not predicted based on the abundance of BRD pathobionts. Lastly, fungal and bacterial co-occurrence were more common in BRD animals than healthy animals.

Discussion

The results from this novel study provide a baseline understanding of the fungal diversity and composition in the nasal cavity of BRD and healthy animals, upon which future interaction studies, including other nasal microbiome members to further understand and accurately diagnose BRD, can be designed.

Detection of Mannheimia haemolytica-Specific IgG, IgM and IgA in Sera and Their Relationship to Respiratory Disease in Cattle

Mannheimia haemolytica is one of the major causes of bovine respiratory disease in cattle. The organism is the primary bacterium isolated from calves and young cattle affected with enzootic pneumonia. Novel indirect ELISAs were developed and evaluated to enable quantification of antibody responses to whole cell antigens using M. haemolytica A1 strain P1148. In this study, the ELISAs were initially developed using sera from both M. haemolytica-culture-free and clinically infected cattle, then the final prototypes were tested in the validation phase using a larger set of known-status M. haemolytica sera (n = 145) collected from feedlot cattle. The test showed good inter-assay and intra-assay repeatability. Diagnostic sensitivity and specificity were estimated at 91% and 87% for IgG at a cutoff of S/P ≥ 0.8. IgM diagnostic sensitivity and specificity were 91% and 81% at a cutoff of sample to positive (S/P) ratio ≥ 0.8. IgA diagnostic sensitivity was 89% whereas specificity was 78% at a cutoff of S/P ≥ 0.2. ELISA results of all isotypes were related to the diagnosis of respiratory disease and isolation of M. haemolytica (p-value < 0.05). These data suggest that M. haemolytica ELISAs can be adapted to the detection and quantification of antibody in serum specimens and support the use of these tests for the disease surveillance and disease prevention research in feedlot cattle.

Pasteurella multocida polyserositis in growing-finishing pigs

Pasteurella multocida is the main secondary bacterium isolated from cases of swine pneumonia. Although highly pathogenic strains of P. multocida have been associated with primary septic lesions and polyserositis in pigs, studies on this pathological presentation in naturally occurring cases are limited. The aim of this work was to characterize the clinical, pathological and molecular findings in cases of P. multocida polyserositis in growing-finishing pigs in a commercial farm in Brazil. The mean age of 17 investigated pigs was 120 days. Clinically, the disease was acute (11/17), with clinical signs of dyspnoea and apathy. Sudden death occurred in some animals (6/17). The main gross findings included fibrinous serositis affecting the abdominal and thoracic cavities (17/17), fibrinous pericarditis (15/17), marked cranioventral pulmonary consolidation (17/17) and splenic infarcts (3/17). P. multocida was isolated in all cases from systemic sites, including the pericardial sac and abdominal exudate. Molecular typing of genus and species was performed on four isolates, and all were characterized as P. multocida type A. Another five isolates were positive for the pathogenicity marker gene pfhA by polymerase chain reaction. This study reinforces the role of P. multocida as a cause of polyserositis in growing-finishing pigs.

The Cell-Mediated Immune Response against Bovine alphaherpesvirus 1 (BoHV-1) Infection and Vaccination

Bovine Alphaherpesvirus 1 (BoHV-1) is one of the major respiratory pathogens in cattle worldwide. Infection often leads to a compromised host immune response that contributes to the development of the polymicrobial disease known as “bovine respiratory disease”. After an initial transient phase of immunosuppression, cattle recover from the disease. This is due to the development of both innate and adaptive immune responses. With respect to adaptive immunity, both humoral and cell-mediated immunity are required to control infection. Thus, several BoHV-1 vaccines are designed to trigger both branches of the adaptive immune system. In this review, we summarize the current knowledge on cell-mediated immune responses directed against BoHV-1 infection and vaccination.

Automated monitoring and detection of disease using a generic facial feature scoring system - A case study on FMD infected cows

Digital images are becoming more readily available and possibilities for image processing are developing rapidly. This opens the possibility to use digital images to monitor and detect diseases in animals. In this paper we present 1) a generic facial feature scoring system based on seven facial features, 2) manual scores of images of Holstein Frisian heifers during foot-and-mouth disease vaccine efficacy trials and 3) automatic disease scores of the same animals. The automatic scoring system was based on the manual version and trained on annotated images from the manual scoring system. For both systems we found an increase in disease scores three days post infection, followed by a recovery. This temporal pattern matched with observations made by animal caretakers. Importantly, the automatic system was able to discern animals that were protected by the vaccine, and did not develop blisters at the feet, and animals that were not protected. Finally, automatic scores could be used to detect healthy and sick animals with a sensitivity and specificity of 0.94 on the second and third days following infection in an experimental setting. This generic facial feature disease scoring system could be further developed and extended to lactating Holstein Frisian dairy cows, other breeds and other infectious diseases. The system could be applied during animal experiments or, after further development, in a farm setting.

A Single Intranasal Dose of Bacterial Therapeutics to Calves Confers Longitudinal Modulation of the Nasopharyngeal Microbiota: a Pilot Study

Bovine respiratory disease (BRD) remains the most significant health challenge affecting the North American beef cattle industry and results in $3 billion in economic losses yearly. Current BRD control strategies mainly rely on antibiotics, with metaphylaxis commonly employed to mitigate BRD incidence in commercial feedlots.

The Bovine Herpesvirus 1 Latency-Reactivation Cycle, a Chronic Problem in the Cattle Industry

Bovine alphaherpesvirus 1 (BoHV-1) is a persistent and recurring disease that affects cattle worldwide. It is a major contributor to bovine respiratory disease and reproductive failure in the US. A major complication of BoHV-1 arises from the lifelong latent infection established in the sensory ganglia of the peripheral nervous system following acute infection. Lifelong latency is marked by periodic reactivation from latency that leads to virus transmission and transient immunosuppression. Physiological and environmental stress, along with hormone fluctuations, can drive virus reactivation from latency, allowing the virus to spread rapidly. This review discusses the mechanisms of the latency/reactivation cycle, with particular emphasis on how different hormones directly regulate BoHV-1 gene expression and productive infection. Glucocorticoids, including the synthetic corticosteroid dexamethasone, are major effectors of the stress response. Stress directly regulates BoHV-1 gene expression through multiple pathways, including β-catenin dependent Wnt signaling, and the glucocorticoid receptor. Related type 1 nuclear hormone receptors, the androgen and progesterone receptors, also drive BoHV-1 gene expression and productive infection. These receptors form feed-forward transcription loops with the stress-induced Krüppel-like transcription factors KLF4 and KLF15. Understanding these molecular pathways is critical for developing novel therapeutics designed to block reactivation and reduce virus spread and disease.

Detection of Pneumocystis and Morphological Description of Fungal Distribution and Severity of Infection in Thirty-Six Mammal Species

Pneumocystis spp. are thought to adapt to the lungs of potentially all mammals. However, the full host range, fungal burden and severity of infection are unknown for many species. In this study, lung tissue samples originating from 845 animals of 31 different families of eight mammal orders were screened by in situ hybridization (ISH) using a universal 18S rRNA probe for Pneumocystis, followed by hematoxylin and eosin (H&E) staining for determining histopathological lesions. A total of 216 (26%) samples were positive for Pneumocystis spp., encompassing 36 of 98 investigated mammal species, with 17 of them being described for the first time for the presence of Pneumocystis spp. The prevalence of Pneumocystis spp. as assessed by ISH varied greatly among different mammal species while the organism load was overall low, suggesting a status of colonization or subclinical infection. Severe Pneumocystis pneumonia seemed to be very rare. For most of the Pneumocystis-positive samples, comparative microscopic examination of H&E- and ISH-stained serial sections revealed an association of the fungus with minor lesions, consistent with an interstitial pneumonia. Colonization or subclinical infection of Pneumocystis in the lung might be important in many mammal species because the animals may serve as a reservoir.

Distinct Mannheimia haemolytica serotypes isolated from fatal infections in veal calves and dairy cows

Fatal Mannheimia haemolytica (M. haemolytica) infections in cattle, which emerged in the Netherlands between 2004 and 2018, showed two distinct disease presentations: acute fibrinous polyserositis (FPS) in veal calves, and acute fibrinous pleuro-pneumonia (FPP) in adult dairy cattle. To determine whether these presentations were caused by different M. haemolytica genotypes, whole genome sequencing was performed on 96 isolates cultured after necropsy from inflamed sites of veal calves that died of M. haemolytica-associated FPS (n = 49) or with FPP lesions (n = 2), and from dairy cows that died of M. haemolytica-associated FPP (n = 45). Among the 96 M. haemolytica isolates, 93 were shown to belong to either of two large clusters, with 48/51 calf isolates belonging to one, and 43/45 cow isolates and two calf isolates from cases of FPP to the other. All M. haemolytica isolates from veal calves with FPS were of serotype A2, whereas the isolates from dairy cows and two calves with FPP were predominantly of serotypes A1 and A6. Most serotype A2 isolates from veal calves with FPS (95.6 %) contained multiple antibiotic resistance genes (ARGs) against three to five antimicrobial classes (phenicols, sulphonamides, tetracyclines, aminoglycosides or beta-lactams). In contrast, these ARGs were only present in 10.8 % of M. haemolytica A1 and A6 isolates from pneumonic adult cattle and absent in isolates from the two calves with FPP. These two disease presentations appear to be caused by genetically distinct strains with different antimicrobial resistance gene patterns. While M. haemolytica serotype A2 is generally considered to be a commensal microorganism of cattle, it was clearly associated with fatal FPS in veal calves in the Netherlands.

Calves severely affected by bovine respiratory disease have reduced protection against histone toxicity and exhibit lower complement activity

Bovine respiratory disease (BRD) remains the greatest challenge facing the beef industry. Calves affected by BRD can manifest illness ranging from subclinical infection to acute death. In pathologies similar to BRD, extracellular histones have been implicated as major contributors to lung tissue damage. Histones are basic proteins responsible for DNA organization in cell nuclei, however when released extracellularly during cell injury or via neutrophil activation they become cytotoxic. Cattle suffering severe cases of BRD demonstrate reduced capacity to protect against the cytotoxic effects of histones, however, the protective mechanism(s) of serum remain(s) unknown. Therefore, the objective was to identify components within serum that contribute to protection against histone toxicity. Serum proteins from animals considered protective (P; N = 4) and nonprotective (NP; N = 4) against the toxic effects of histones were precipitated by the addition and incubation of exogenous histones. Proteins that interact with histones from both groups were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified via label free "shotgun" proteomics. Sixteen candidate proteins increased by ≥2-fold change in P vs. NP animals were identified, with several associated with the complement system. A subsequent study was conducted to evaluate complement system activity and serum protective capacity against exogenous histones in feedlot heifers. Serum samples were collected from 118 heifer calves (BW at arrival = 229 ± 2.4 kg) at feedlot arrival. Animals were retrospectively assigned to groups consisting of: calves not requiring treatment with antibiotics for BRD (CONT; N = 80), calves treated once (1TRT; N = 21), calves treated twice (2TRT; N = 5), calves treated thrice (3TRT; N = 3), or calves that died from BRD within 1 wk of entering the feedlot (DA; N = 9). Serum from DA animals was less protective than CONT (P = 0.0005) animals against histone toxicity. Complement activity of DA animals was reduced compared to CONT (P = 0.0044) animals. Additionally, the use of both assays as a ratio resulted in increased ability to detect DA animals. Results suggest that cattle predisposed to severe cases of respiratory disease may have impaired complement activity presumably contributing to reduced protective capacity against histone toxicity.

The influence of passive colostrum transfer on humoral immunity to selected antigens of Mannheimia haemolytica in calves

The aim of the study was to evaluate the effectiveness of colostral immunity against aetiological agents of bovine respiratory disease complex (BRDC), to assess the suppressive effect of colostral antibodies against Mannheimia haemolytica on immunity, and to analyse acute phase proteins in calves. Holstein-Friesian and Simmental cows and calves were immunized with M. haemolytica leukotoxin (Lkt) and outer membrane proteins (OMPs) at 6 and 4 weeks before parturition. Sera and colostrum were collected from the cows directly after calving. Sera from calves were obtained before colostrum intake and 48 h after birth. Calves from vaccinated and unvaccinated cows were placed in the feedlot and immunized with Lkt or OMP on days 10 and 24. Calves were tested for serum antibodies against respiratory viruses. Trachea and lung samples were collected for bacteriological examination from all calves that had died with BRDC. The results indicated high colostrum values and IgG transfer in calves at 48 h (> 12.5 g/l) and a high concentration of anti-BVD antibodies in calves at 48 h (> 33–45 mg/ml). Similar values were observed for bovine herpes virus BHV-1 and bovine respiratory sycytil virus BRSV. Immunoglobulin concentrations were highest for antibodies specific to parainfluenza PI-3 and adenoviruses. The lowest antibody levels were detected against M. haemolytica antigens in all experimental groups of calves (< 50 mg/ml in calves of cows vaccinated with M. haemolytica antigens and < 25 mg/ml in calves of unvaccinated cows). The findings indicate the need for early immunization of calves, which is often precluded by stress associated with transport and adaptation to the new conditions in the feedlot.

Applying multi-omics data to study the genetic background of bovine respiratory disease infection in feedlot crossbred cattle

Bovine respiratory disease (BRD) is the most common and costly infectious disease affecting the wellbeing and productivity of beef cattle in North America. BRD is a complex disease whose development is dependent on environmental factors and host genetics. Due to the polymicrobial nature of BRD, our understanding of the genetic and molecular mechanisms underlying the disease is still limited. This knowledge would augment the development of better genetic/genomic selection strategies and more accurate diagnostic tools to reduce BRD prevalence. Therefore, this study aimed to utilize multi-omics data (genomics, transcriptomics, and metabolomics) analyses to study the genetic and molecular mechanisms of BRD infection. Blood samples of 143 cattle (80 BRD; 63 non-BRD animals) were collected for genotyping, RNA sequencing, and metabolite profiling. Firstly, a genome-wide association study (GWAS) was performed for BRD susceptibility using 207,038 SNPs. Two SNPs (Chr5:25858264 and BovineHD1800016801) were identified as associated (p-value <1 × 10-5) with BRD susceptibility. Secondly, differential gene expression between BRD and non-BRD animals was studied. At the significance threshold used (log2FC>2, logCPM>2, and FDR<0.01), 101 differentially expressed (DE) genes were identified. These DE genes significantly (p-value <0.05) enriched several immune responses related functions such as inflammatory response. Additionally, we performed expression quantitative trait loci (eQTL) analysis and identified 420 cis-eQTLs and 144 trans-eQTLs significantly (FDR <0.05) associated with the expression of DE genes. Interestingly, eQTL results indicated the most significant SNP (Chr5:25858264) identified via GWAS was a cis-eQTL for DE gene GPR84. This analysis also demonstrated that an important SNP (rs209419196) located in the promoter region of the DE gene BPI significantly influenced the expression of this gene. Finally, the abundance of 31 metabolites was significantly (FDR <0.05) different between BRD and non-BRD animals, and 17 of them showed correlations with multiple DE genes, which shed light on the interactions between immune response and metabolism. This study identified associations between genome, transcriptome, metabolome, and BRD phenotype of feedlot crossbred cattle. The findings may be useful for the development of genomic selection strategies for BRD susceptibility, and for the development of new diagnostic and therapeutic tools.

Sodium butyrate pretreatment mitigates lipopolysaccharide-induced inflammation through the TLR4/NF-κB signaling pathway in bovine embryo trachea cells

The present study investigated the anti-inflammatory effects and potential mechanisms of sodium butyrate (SB) in bovine embryo tracheal cells (EBTr) stimulated with lipopolysaccharide (LPS). EBTr were exposed to either 1 mmol/L SB for 18 h for the SB group (SB) or to 0.4 μg/mL LPS for 6 h for the LPS group (LPS). PBS was added to EBTr for a control group (CON). EBTr were pretreated with SB for 18 h followed by 6 h of LPS stimulation for the LSB group (LSB). Results showed that with LPS stimulation, the gene expression of TLR4, NF-κB, IL6, and IL8, as well as cytokine production of IL6 and TNF-α, were significantly increased compared with the CON group. In contrast, protein expression of IL10 was decreased. However, these inflammatory effects induced by LPS were reversed in the LSB group. Compared with the CON group, protein expression of TLR4, phospho-NF-κB p65, phospho-IκBα, and IL1α were increased in the LPS group and these were decreased in the LSB group. Similarly, increased nuclear translocation of phospho-NF-κB p65 in the LPS group was suppressed with SB pretreatment. In conclusion, SB can reduce inflammation induced by LPS in EBTr, and this positive effect is mediated through the TLR4 and NF-κB signaling pathway.

Reduction in Mortality of Calves with Bovine Respiratory Disease in Detection with Influenza C and D Virus

Both influenza C (ICV) and influenza D (IDV) viruses were recently included as bovine respiratory disease (BRD) causes, but their role in BRD has not been evaluated. Therefore, the mortality and reproductive performances of BRD calves with different isolated viruses were determined in this study. Data on 152 BRD calves with bovine viral diarrhoea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine coronavirus (BCoV), bovine parainfluenza virus 3 (BPIV-3), ICV, or IDV from nasal swab samples using real-time rt-PCR were used. The general data and respiratory signs were recorded immediately, and thereafter, the data on dead or culling calves due to BRD and reproductive performance were collected. The percentages of the BRD calves were 71.7%, 52.6%, 40.8%, 10.5%, 68.4%, and 65.8% for BVDV, BRSV, BCoV, BPIV-3, ICV, and IDV, respectively. Mucous secretion (OR = 4.27) and age ≤ 6 months (OR =14.97) had higher risks of mortality than those with serous secretion and older age. The calves with IDV had lower risks of culling than those without IDV (OR = 0.19). This study shows that most viral infections in BRD calves are a combination of viruses with BVDV, ICV, and IDV. In addition, IDV might have a role in reducing the severity of BRD calves.

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.

Mannheimia haemolytica OmpH binds fibrinogen and fibronectin and participates in biofilm formation

Mannheimia haemolytica is the causal agent of the shipping fever in bovines and produces high economic losses worldwide. This bacterium possesses different virulence attributes to achieve a successful infection. One of the main virulence factors expressed by a pathogen is through adhesion molecules; however, the components participating in this process are not totally known. The present work identified a M. haemolytica 41 kDa outer membrane protein (Omp) that participates in bacterial adhesion. This protein showed 100% identity with the OmpH from M. haemolytica as determined by mass spectrometry and it interacts with sheep fibrinogen. The 41 kDa M. haemolytica OmpH interacts with bovine monocytes; a previous incubation of M. haemolytica with a rabbit hyperimmune serum against this Omp diminished 45% cell adhesion. The OmpH was recognized by serum from bovines affected by acute or chronic pneumonia, indicating its in vivo expression; moreover, it showed immune cross-reaction with the serum of rabbit infected with Pasteurella multocida. The OmpH is present in biofilms and previous incubation of M. haemolytca with rabbit serum against this protein diminished biofilm, indicating this protein's participation in biofilm formation. M. haemolytica OmpH is proposed as a relevant immunogen in bovine pneumonia protection.

Geography, niches, and transportation influence bovine respiratory microbiome and health

Bovine respiratory disease (BRD), one of the most common and infectious diseases in the beef industry, is associated with the respiratory microbiome and stressors of transportation. The impacts of the bovine respiratory microbiota on health and disease across different geographic locations and sampling niches are poorly understood, resulting in difficult identification of BRD causes. In this study, we explored the effects of geography and niches on the bovine respiratory microbiome and its function by re-analyzing published metagenomic datasets and estimated the main opportunistic pathogens that changed after transportation. The results showed that diversity, composition, structure, and function of the bovine nasopharyngeal microbiota were different across three worldwide geographic locations. The lung microbiota also showed distinct microbial composition and function compared with nasopharyngeal communities from different locations. Although different signature microbiota for each geographic location were identified, a module with co-occurrence of Mycoplasma species was observed in all bovine respiratory communities regardless of geography. Moreover, transportation, especially long-distance shipping, could increase the relative abundance of BRD-associated pathogens. Lung microbiota from BRD calves shaped clusters dominated with different pathogens. In summary, geography, sampling niches, and transportation are important factors impacting the bovine respiratory microbiome and disease, and clusters of lung microbiota by different bacterial species may explain BRD pathogenesis, suggesting the importance of a deeper understanding of bovine respiratory microbiota in health.

Understanding the mechanisms of viral and bacterial coinfections in bovine respiratory disease: a comprehensive literature review of experimental evidence

Bovine respiratory disease (BRD) is one of the most important diseases impacting the global cattle industry, resulting in significant economic loss. Commonly referred to as shipping fever, BRD is especially concerning for young calves during transport when they are most susceptible to developing disease. Despite years of extensive study, managing BRD remains challenging as its aetiology involves complex interactions between pathogens, environmental and host factors. While at the beginning of the twentieth century, scientists believed that BRD was only caused by bacterial infections ("bovine pasteurellosis"), we now know that viruses play a key role in BRD induction. Mixtures of pathogenic bacteria and viruses are frequently isolated from respiratory secretions of animals with respiratory illness. The increased diagnostic screening data has changed our understanding of pathogens contributing to BRD development. In this review, we aim to comprehensively examine experimental evidence from all existing studies performed to understand coinfections between respiratory pathogens in cattle. Despite the fact that pneumonia has not always been successfully reproduced by in vivo calf modelling, several studies attempted to investigate the clinical significance of interactions between different pathogens. The most studied model of pneumonia induction has been reproduced by a primary viral infection followed by a secondary bacterial superinfection, with strong evidence suggesting this could potentially be one of the most common scenarios during BRD onset. Different in vitro studies indicated that viral priming may increase bacterial adherence and colonization of the respiratory tract, suggesting a possible mechanism underpinning bronchopneumonia onset in cattle. In addition, a few in vivo studies on viral coinfections and bacterial coinfections demonstrated that a primary viral infection could also increase the pathogenicity of a secondary viral infection and, similarly, dual infections with two bacterial pathogens could increase the severity of BRD lesions. Therefore, different scenarios of pathogen dynamics could be hypothesized for BRD onset which are not limited to a primary viral infection followed by a secondary bacterial superinfection.

Seminal and histopathological alterations in bucks challenged with Mannheimia haemolytica serotype a2 and its LPS endotoxin

Pneumonic mannheimiosis is a widespread respiratory bacterial disease of small ruminants caused by Mannheimia haemolytica serotype A2. The disease is known to affect the respiratory organs of infected animals, but its effect on other vital and reproductive organs has not been fully explored. Previous studies have demonstrated increased serum pro-inflammatory cytokine concentration post-challenge with M. haemolytica A2 and its LPS, indicating systemic inflammation in the host. This study determined the potential tissue changes and alterations of sperm parameters due to infection of M. haemolytica A2 and its LPS endotoxin. In this study, twelve experimental bucks were randomly assigned to three groups of four bucks each: group 1 (control group) were intranasally inoculated with 2 mL of PBS pH 7.0, group 2 received 2 mL of 1.2 × 10⁹ CFU/mL M. haemolytica A2 intranasally, and group 3 received 2 mL of LPS extracted from 1.2 × 10⁹ CFU/mL of M. haemolytica A2 intravenously. Semen samples were collected at pre-determined intervals using an electro-ejaculator and analysed immediately after collection. All experimental bucks were slaughtered via exsanguination on day 60 to collect their vital and reproductive organs at necropsy, and the samples were processed and analysed for histopathological changes. The current study has revealed that bucks challenged with M. haemolytica A2 and its LPS exhibited alterations in semen parameters such as motility, wave pattern, viability, and morphological abnormalities. Mild to moderate histopathological changes of the lung, liver, testis, epididymis, vas deferens, prostate, and lymph nodes were also observed in both challenged groups. Therefore, this study revealed the potential harmful effects of respiratory mannheimiosis on the reproductive organs of the infected bucks and sheds light on the expanse of systemic effects of this disease.

Mycoplasma bovis is associated with Mannheimia haemolytica during acute bovine respiratory disease in feedlot cattle

Bovine Respiratory Disease (BRD) represents a significant burden to the health of feedlot cattle and the profitability of the beef industry in the US. Mannheimia haemolytica is widely regarded as the primary bacterial pathogen driving acute BRD. While Mycoplasma bovis is most commonly implicated in chronic cases of BRD, this agent's potential role in acute stages of BRD is unclear. Therefore, this study aimed to evaluate potential associations between M. bovis and M. haemolytica during acute BRD in feedlot cattle. Nasal swabs (n = 1,044) were collected over time from feedlot cattle (n = 270) enrolled in an experiment assessing the effect of vaccination for Bovine Respiratory Syncytial Virus (BRSV). Swabs were analyzed for detection of M. bovis, M. haemolytica, Pasteurella multocida, Histophilus somni, and BRSV via multiplex qPCR assays. Data were analyzed using inverse conditional probability weighted (ICPW) logistic regression models to investigate potential effects of M. bovis presence on arrival (d0), day seven (d7) and day 14 (d14) post-arrival on M. haemolytica prevalence on day 28 (d28) post-arrival, adjusting for the previous history of P. multocida, H. somni, BRSV, BRD morbidity, and body weight. The potential association between time-to-BRD detection and M. bovis presence on d0, d7, and d14 post-arrival, was inferred via an ICPW time-to-event model. The presence of M. bovis in nasal swabs collected on d7 post-arrival was significantly associated with an increase in the prevalence of M. haemolytica on d28 (prevalence difference: 45%; 95% Confidence Interval: 31%, 60%; P-value < 0.001). Significant time-varying coefficients for M. bovis presence were detected at d0, d7, and d14 post-arrival in the ICPW time-to-event model (P-value < 0.001). The shortest median time-to-BRD detection was 29 days in cattle that were M. bovis positive on d0, d7, and d14 post-arrival and in those that were positive on d0 and d14 post-arrival. Under the conditions of this study, our findings suggest that M. bovis may be influencing the respiratory environment during the acute phase of BRD, increasing the abundance of M. haemolytica, which could have important impacts on the occurrence of BRD.

Utilizing the Gastrointestinal Microbiota to Modulate Cattle Health through the Microbiome-Gut-Organ Axes

The microorganisms inhabiting the gastrointestinal tract (GIT) of ruminants have a mutualistic relationship with the host that influences the efficiency and health of the ruminants. The GIT microbiota interacts with the host immune system to influence not only the GIT, but other organs in the body as well. The objective of this review is to highlight the importance of the role the gastrointestinal microbiota plays in modulating the health of a host through communication with different organs in the body through the microbiome-gut-organ axes. Among other things, the GIT microbiota produces metabolites for the host and prevents the colonization of pathogens. In order to prevent dysbiosis of the GIT microbiota, gut microbial therapies can be utilized to re-introduce beneficial bacteria and regain homeostasis within the rumen environment and promote gastrointestinal health. Additionally, controlling GIT dysbiosis can aid the immune system in preventing disfunction in other organ systems in the body through the microbiome-gut-brain axis, the microbiome-gut-lung axis, the microbiome-gut-mammary axis, and the microbiome-gut-reproductive axis.

EXPLORING THE USE OF THE ERYTHROCYTE SEDIMENTATION RATE AS AN INFLAMMATORY MARKER FOR FREE-RANGING WILDLIFE: A CASE STUDY IN AFRICAN BUFFALO (SYNCERUS CAFFER)

Measuring inflammatory markers is critical to evaluating both recent infection status and overall human and animal health; however, there are relatively few techniques that do not require specialized equipment or personnel for detecting inflammation among wildlife. Such techniques are useful in that they help determine individual and population-level inflammatory status without the infrastructure and reagents that many more-specific assays require. One such technique, known as the erythrocyte sedimentation rate (ESR), is a measure of how quickly erythrocytes (red blood cells) settle in serum, with a faster rate indicating a general, underlying inflammatory process is occurring. The technique is simple, inexpensive, and can be performed in the field without specialized equipment. We took advantage of a population of African buffalo (Syncerus caffer), well studied from June 2014 to May 2017, to understand the utility of ESR in an important wildlife species. When ESR was compared with other markers of immunity in African buffalo, it correlated to known measures of inflammation. We found that a faster ESR was significantly positively correlated with increased total globulin levels and significantly negatively correlated with increased red blood cell count and albumin levels. We then evaluated if ESR correlated to the incidence of five respiratory pathogens and infection with two tick-borne pathogens in African buffalo. Our results suggest that elevated ESR is associated with the incidence of bovine viral diarrhea virus infection, parainfluenza virus, and Mannheimia haemolytica infections as well as concurrent Anaplasma marginale and Anaplasma centrale coinfection. These findings suggest that ESR is a useful field test as an inflammatory marker in individuals and herds, helping us better monitor overall health status in wild populations.

Isolation and Molecular Detection of Pasteurellosis from Pneumonic Sheep in Selected Areas of Amhara Region, Ethiopia: An Implication for Designing Effective Ovine Pasteurellosis Vaccine

Introduction

Methods

Results

Discussion and conclusion