The biology and development of vaccines for bovine alphaherpesvirus 1

Bovine alphaherpesvirus type 1 (BoAHV-1) infections lead to compromised herd health and significantly reduced productivity of affected cattle. While BoAHV-1 may cause rhinotracheitis, conjunctivitis, genital infections, and abortions, respiratory tract infections constitute the predominant clinical disease. Immune suppression induced by BoAHV-1 may contribute to co-infections initiating the bovine respiratory disease complex. In this review, the emphasis is to recapitulate the biology and the vaccine technologies currently in use and in development for BoAHV-1, and to discuss the major limitations. Studies on the life cycle and host interactions of BoAHV-1 have resulted in the identification of virulence factors. While several vaccine types, such as vectored vaccines and subunit vaccines, are under investigation, modified live and inactivated BoAHV-1 vaccines are still most frequently used in most areas of the world, whereas attenuated and inactivated marker vaccines are in use in Europe. The knowledge gained from studies on the biology of BoAHV-1 can form a basis for the rational design of future vaccines.

Graduate Student Literature Review: Role of antioxidants in calf immunity, growth, and health

The neonatal period for dairy calves is crucial for immune, metabolic, and physical development, which opens a window of disease susceptibility. Although the industry has relied on tools such as colostrum and vaccination to support early life immunity, there are several challenges when vaccinating neonatal calves: (1) the inability to mount an effective immune response, (2) interference with maternal antibodies, and (3) oxidative stress (OS). Oxidative stress is characterized as the imbalance of pro-oxidants to antioxidants that results in cellular oxidative damage or dysfunction. Oxidative stress has become a topic of interest in the neonatal period because it negatively affects lymphocyte function, which might affect vaccine response. Widely studied in mature cattle, antioxidant supplementation has the potential to improve reduction-oxidation balance and immune response. Evidence supporting the use of antioxidants such as vitamins and minerals in neonatal calves is far scarcer but necessary to optimize immunity and disease resistance. This review summarizes research on the effect of antioxidant supplementation on calf immunity, health, and productivity and highlights remaining gaps in knowledge. Overall, micronutrient supplementation, including vitamins and minerals, in preweaning and postweaning calves improved immune responses but there is conflicting evidence supporting the subsequent positive effect on calf health and growth performance.

Identifying and addressing barriers and opportunities for bovine respiratory disease complex vaccination: a consensus paper on practical recommendations for best practise vaccination

Many questions are raised, and challenges faced in the new era of (intranasal) bovine respiratory disease complex vaccination. An increase in vaccination rate is expected, due to its positive impact on cattle health, reduction of antimicrobial use and economic factors. However, engagement of farmers and veterinarians with regard to vaccination is often affected by limitations, resulting in the development of barriers to vaccination, but also opportunities to overcome these. The objective of the report is to provide practical recommendations and a consensus on best practises for BRDC vaccination, addressing barriers faced by veterinarians and farmers. The report combines an evidence review with expert opinions and includes discussions on different vaccination approaches, such as intranasal and systemic protocols. As result of the discussions, several barriers to BRDC vaccination were identified, including a lack of knowledge or visibility of the disease's impact, the preference for blanket antibiotic use over vaccination, resistance to change, the need for visible success, uncertainty about the best time to vaccinate, and concerns about adverse reactions and vaccine efficacy in the presence of maternal antibodies. While these barriers seem substantial, they provide opportunities for the veterinary sector. Indeed, veterinarians are encouraged to use the argumentation presented, along with local case studies and diagnostic testing to highlight the impact of disease, while conducting calf health audits, ensuring expectations are managed to achieve visible success. Overall, this consensus paper aims to provide practical recommendations and support for veterinarians and farmers to overcome barriers and increase BRDC vaccination rates in cattle.

Investigation into the safety, and serological responses elicited by delivery of live intranasal vaccines for bovine herpes virus type 1, bovine respiratory syncytial virus, and parainfluenza type 3 in pre-weaned calves

Despite the fact that pneumonia remains a leading cause of mortality and morbidity in pre-weaned calves, relatively little is known regarding the effects of the concurrent administration of intranasal pneumonia virus vaccines, particularly in calves with high levels of maternally derived antibodies. The objective of this study was to use a cohort of 40 dairy and dairy-beef female and male calves (27 females and 13 males) to determine serological responses to concurrent administration at 3 weeks of age (22 ± 4.85 days) of two commercially available intranasal (IN) vaccines for the viruses: bovine respiratory syncytial virus (BRSV), bovine herpes virus 1 (BoHV-1), and parainfluenza-3-virus (PI3-V). The study groups were as follows: (i) Bovilis IBR Marker Live only® (IO), (ii) Bovilis INtranasal RSP Live® only (RPO), (iii) Concurrent vaccination with Bovilis IBR Marker Live® & Bovilis Intranasal RSP Live® (CV), and (iv) a control group of non-vaccinated calves (CONT). The calves' serological response post-IN vaccination, clinical health scores, rectal temperatures, and weights were measured. Data were analyzed in SAS using mixed models and logistic regression. The CV calves had an average daily weight gain (ADG) of 0.74 (±0.02) kg, which was similar to CONT (0.77 ± 0.02 kg). Despite no significant differences in the antibody levels between study groups 3 weeks post-IN vaccination, following the administration of subsequent parenteral injections in the form of Bovilis Bovipast RSP®(antigens; inactivated BRSV, inactivated PI3-V, inactivated Mannheimia haemolytica) and Bovilis IBR Marker Live®, the antibody levels of the BRSV and PI3-V increased in both the CV and RPO study groups. Concurrent vaccination resulted in no increase in fever and no difference in health scores when compared to CONT.

Histological Characteristics of Conjunctiva-Associated Lymphoid Tissue in Young and Adult Holstein Cattle

The conjunctiva-associated lymphoid tissue (CALT) has been used as a target site for mucosal vaccinations in several animals. In this study, we compared the morphological features of CALT in the eyelid and third eyelid between Holstein calves and adult cows. In the eyelids, CALTs in the form of diffused lymphoid tissue (DLT) and lymphatic follicles (LF) were observed, where DLTs were dominant and LFs were scarce. The CALTs of cows comprised T-, B-cells, macrophages, and antigen-presenting cells (APCs). In particular, B-cells were dominant except in the eyelids of the calves. The epithelial layer covering the CALT is often discontinuous and lacks goblet cells. Cytokeratin18 is strongly expressed in the epithelial layer covering the CALT, except in the third eyelids of adult cows. IgA-positive cells were diffusely distributed in the lamina propria of the conjunctiva of the eyelids and third eyelids. The eyelid CALT area in calves was lower than that in adult cows. Furthermore, the CALT of calves had a lower cellularity of B-cells and a higher cellularity of macrophages than that of adult cows. These histological characteristics indicate that CALT plays a role in the mucosal immune-inductive and effector sites. Furthermore, lower cellularity of B-cells in the CALT of calves indicates that the function of CALT as a mucosal immune induction site is less developed in calves than in adult cows.

Effect of maternal separation and transportation stress on the bovine upper respiratory tract microbiome and the immune response to resident opportunistic pathogens

Background

The bovine upper respiratory tract (URT) microbiome includes opportunistic pathogens that cause respiratory disease and stress associated with maternal separation and transportation contributes to the severity of this respiratory disease. Stress is known to alter the gut microbiome but little is known regarding the effect of stress on the URT microbiota. This study used six-month old suckling beef calves to investigate whether maternal separation (weaned), by itself or combined with transportation (weaned + transport), altered the URT microbiome and host immune responses to resident opportunistic pathogens.

Results

Taxonomic and functional composition of the URT microbiome in suckling and weaned beef calves did not change significantly when serially sampled over a one-month period. Subtle temporal changes in the URT microbiome composition were observed in weaned + transport calves. Total bacterial density was lower (p < 0.05) on day 4 post-weaning in both the weaned and weaned + transport groups when compared to suckling calves. In addition, significant (p < 0.05) temporal changes in the density of the opportunistic pathogens, M. haemolytica and P. multocida, were observed independent of treatment but these changes did not correlate with significantly increased (p < 0.05) serum antibody responses to both of these bacteria in the weaned and weaned + transport groups. Serum antibody responses to My. bovis, another opportunistic pathogen, remained unchanged in all treatment groups. Weaning, by itself and in combination with transportation, also had significant (p < 0.05) short- (2 to 8 days post-weaning) and long-term (28 days post-weaning) effects on the expression of adrenergic receptor genes in blood leukocytes when compared to age-matched suckling beef calves.

Conclusions

Maternal separation (weaning) and transportation has minor effects on the taxonomic and functional composition of the URT microbiome and temporal changes in the density of opportunistic pathogen residing in the URT did not correlate with significant changes in immune responses to these bacteria. Significant changes in adrenergic receptor expression in blood leukocytes following weaning, with or without transportation, suggests altered neuroimmune regulation should be further investigated as a mechanism by which stress can alter host-microbiome interactions for some opportunistic respiratory pathogens that reside in the URT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00123-2.

Evaluation of specific immunoglobulin A in nasal secretions and neutralizing antibodies in serum collected at multiple time points from young beef calves following intranasal or subcutaneous administration of a modified-live bovine respiratory syncytial virus vaccine

OBJECTIVE

To determine anti-bovine respiratory syncytial virus (BRSV) antibody titers for nasal secretions and serum from beef calves following administration of a modified-live (MLV) BRSV vaccine.

ANIMALS

60 healthy newborn purebred beef calves.

PROCEDURES

Calves were randomly assigned to 1 of 3 groups: intranasal (IN)-SC (IN MLV BRSV vaccine within 24 hours of birth and SC MLV BRSV vaccine at 2 months of age), SC-IN (SC MLV BRSV vaccine within 24 hours of birth and IN MLV BRSV vaccine at 2 months of age), or NO-IN (no vaccine within 24 hours of birth and IN MLV BRSV vaccine at 2 months of age). Nasal secretion and serum samples were collected for determination of anti-BRSV antibodies within 24 hours of birth and 2 and 6 months of age.

RESULTS

Titers of anti-BRSV IgA antibodies in nasal secretions and BRSV neutralizing antibodies in serum were similar among groups at each sampling time. Within 24 hours of birth, nasal anti-BRSV IgA titers were negligible. At 2 months, mean nasal anti-BRSV IgA titers for calves in IN-SC, SC-IN, and NO-IN groups were 192.84, 224.49, and 114.71, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Concentrations of anti-BRSV IgA antibodies in the nasal secretions and BRSV neutralizing antibodies in the serum of young beef calves following an MLV BRSV vaccine protocol that consisted of IN or SC vaccine within 24 hours of birth and vice versa at 2 months of age were not different from that following only an IN MLV BRSV vaccine at 2 months of age. However, the lack of any differences may have been attributed to other factors.

Comparison of the immune response following subcutaneous versus intranasal modified-live virus booster vaccination against bovine respiratory disease in pre-weaning beef calves that had received primary vaccination by the intranasal route

This study was performed to elucidate whether the route of booster vaccination affects the immune response against respiratory vaccine viruses in pre-weaning beef calves that receive primary intranasal (IN) vaccination during the first month of life. The objective was to compare the serum neutralizing antibody (SNA) titers to BHV1, BRSV, and BPI3V, cytokine mRNA expression and mucosal BHV1- and BRSV-specific IgA in nasal secretions following administration of IN or subcutaneous (SC) modified-live virus (MLV) booster vaccines 60 days after primary IN vaccination in young beef calves. Twenty-one beef calves were administered 2 mL of an IN MLV vaccine containing BHV1, BRSV, and BPI3V (Inforce3®) between one and five weeks of age. Sixty days after primary vaccination, calves were randomly assigned to one of two groups: IN-MLV (n = 11): Calves received 2 mL of the same IN MLV vaccine used for primary vaccination and 2 mL of a SC MLV vaccine containing BVDV1 & 2 (Bovi- Shield GOLD® BVD). SC-MLV (n = 10): Calves were administered 2 mL of a MLV vaccine containing, BHV1, BRSV, BPI3V, and BVDV1 & 2 (Bovi-Shield GOLD® 5). Blood and nasal secretion samples were collected on days -61 (primary vaccination), -28, -14, 0 (booster vaccination), 14, 21, 28, 42 and 60 for determination of SNA titers, cytokine gene expression analysis and nasal virus-specific IgA concentrations. Statistical analysis was performed using a repeated measures analysis through PROC GLIMMIX of SAS®. Booster vaccination by neither IN nor SC routes induced a significant increase in SNA titers against BHV1, BRSV, and BPI3V. Subcutaneous booster vaccination induced significantly greater BRSV-specific SNA titers (on day 42) and IgA concentration in nasal secretions (on days 21 and 42) compared to calves receiving IN booster vaccination. Both IN and SC booster vaccination were able to stimulate the production of BHV1-specific IgA in nasal secretions. In summary, booster vaccination of young beef calves using either SC or IN route two months after IN MLV primary vaccination resulted in comparable SNA titers, cytokine gene expression profile and virus-specific IgA concentration in nasal secretions. Only a few differences in the systemic and mucosal immune response against BHV1 and BRSV were observed. Subcutaneous booster vaccination induced significantly greater BRSV-specific SNA and secretory IgA titers compared to IN booster vaccination.

Innate and acquired immune responses of colostrum-fed neonatal Holstein calves following intranasal vaccination with two commercially available modified-live virus vaccines

OBJECTIVE

To compare immune responses induced by 2 commercially available vaccines with a bovine herpesvirus type 1 (BHV1) component following intranasal (IN) administration to colostrum-fed calves.

ANIMALS

90 male Holstein calves (ages, 5 to 14 days).

PROCEDURES

In a randomized complete block design, each calf received 2 mL (1 mL/nostril) of vaccine A (n = 30), vaccine B (30), or saline (0.9% NaCl) solution (30) on day 0. Blood samples were collected for determination of serum anti-BHV1 IgG titer, and nasal fluid (NF) samples were collected for determination of interferon (IFN)-α and IFN-γ concentrations and for secretory IgA titers against BHV1, Mannheimia haemolytica, and Pasteurella multocida at predetermined times for 42 days after vaccination.

RESULTS

All calves were seropositive for anti-BHV1 IgG, and the mean anti-BHV1 IgG titer did not differ significantly among the 3 groups at any time. Both vaccines induced significant transient increases in NF IFN-α and IFN-γ concentrations. On day 5, mean IFN-α concentration and the proportion of calves with detectable IFN-α concentrations for the vaccine A group were significantly greater than those for the vaccine B and control groups. On day 42, the mean NF anti-P multocida IgA titers for both vaccine groups were significantly greater than that of the control group.

CONCLUSIONS AND CLINICAL RELEVANCE

Both vaccines induced innate and acquired immune responses in calves with colostral antibodies. The magnitude of the IFN-α response and proportion of calves with detectable IFN-α differed between the 2 vaccine groups. Both vaccines appeared to enhance the IgA response against P multocida.

Immunity and Protective Efficacy of Mannose Conjugated Chitosan-Based Influenza Nanovaccine in Maternal Antibody Positive Pigs

Parenteral administration of killed/inactivated swine influenza A virus (SwIAV) vaccine in weaned piglets provides variable levels of immunity due to the presence of preexisting virus specific maternal derived antibodies (MDA). To overcome the effect of MDA on SwIAV vaccine in piglets, we developed an intranasal deliverable killed SwIAV antigen (KAg) encapsulated chitosan nanoparticles called chitosan-based NPs encapsulating KAg (CS NPs-KAg) vaccine. Further, to target the candidate vaccine to dendritic cells and macrophages which express mannose receptor, we conjugated mannose to chitosan (mCS) and formulated KAg encapsulated mCS nanoparticles called mannosylated chitosan-based NPs encapsulating KAg (mCS NPs-KAg) vaccine. In MDA-positive piglets, prime-boost intranasal inoculation of mCS NPs-KAg vaccine elicited enhanced homologous (H1N2-OH10), heterologous (H1N1-OH7), and heterosubtypic (H3N2-OH4) influenza virus-specific secretory IgA (sIgA) antibody response in nasal passage compared to CS NPs-KAg vaccinates. In vaccinated upon challenged with a heterologous SwIAV H1N1, both mCS NPs-KAg and CS NPs-KAg vaccinates augmented H1N2-OH10, H1N1-OH7, and H3N2-OH4 virus-specific sIgA antibody responses in nasal swab, lung lysate, and bronchoalveolar lavage (BAL) fluid; and IgG antibody levels in lung lysate and BAL fluid samples. Whereas, the multivalent commercial inactivated SwIAV vaccine delivered intramuscularly increased serum IgG antibody response. In mCS NPs-KAg and CS NPs-KAg vaccinates increased H1N2-OH10 but not H1N1-OH7 and H3N2-OH4-specific serum hemagglutination inhibition titers were observed. Additionally, mCS NPs-KAg vaccine increased specific recall lymphocyte proliferation and cytokines IL-4, IL-10, and IFNγ gene expression compared to CS NPs-KAg and commercial SwIAV vaccinates in tracheobronchial lymph nodes. Consistent with the immune response both mCS NPs-KAg and CS NPs-KAg vaccinates cleared the challenge H1N1-OH7 virus load in upper and lower respiratory tract more efficiently when compared to commercial vaccine. The virus clearance was associated with reduced gross lung lesions. Overall, mCS NP-KAg vaccine intranasal immunization in MDA-positive pigs induced a robust cross-reactive immunity and offered protection against influenza virus.

Effectiveness of two intranasal vaccines for the control of bovine respiratory disease in newborn beef calves: A randomized non-inferiority multicentre field trial

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Multicentre field trials with natural pathogen exposure complement challenge trials.

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Beef calves housed with their dams were assessed for bovine respiratory disease (BRD).

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Two commercial intranasal live vaccines for BRSV-bPI3V were evaluated.

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New Vaccine A demonstrated non-inferiority compared to benchmarked Vaccine B.

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Difference in BRD prevalence between Vaccines A and B was −0.4% (95% CI −1.6 to 0.8%).

Bovine respiratory syncytial virus (BRSV) and bovine parainfluenza-3 virus (bPI3V) are major causes of bovine respiratory disease (BRD) in newborn calves worldwide. Vaccination is widely used to prevent BRD, and intranasal vaccines for BRSV and bPI3V were developed to overcome interference from BRSV and bPI3V-specific maternally derived antibodies. Many experimental challenge trials have demonstrated that intranasal vaccines for BRSV and bPI3V are efficacious, but effectiveness under field conditions has been demonstrated less often, especially for newborn beef calves. The objective of this field trial was to compare the effectiveness of a newly available commercial BRSV-bPI3V intranasal vaccine with that of a benchmarked one in newborn beef calves reared in a cow-calf system. A total of 935 calves from 39 farms were randomized into two vaccine groups (Bovalto Respi Intranasal [Vaccine A], n = 468; Rispoval RS + PI3 Intranasal [Vaccine B], n = 467), and monitored during the in-house risk period up to three months after vaccination. Non-inferiority analysis was performed by calculating the difference in BRD prevalence between the two vaccine groups.

No significant differences were observed between vaccines regarding clinical outcomes of morbidity, mortality, duration between vaccination and BRD occurrence, or treatments required. Because the upper limit of the 2-sided 95% confidence interval of the difference in BRD prevalence between the two treatment groups (0.8%) was less than the margin of non-inferiority (δ = 5%), a non-inferiority of Vaccine A was concluded. In conclusion, Vaccine A is at least as effective as Vaccine B for the prevention of BRD in newborn beef cattle in a cow-calf system under field conditions.

Bovine Respiratory Disease Vaccination Against Viral Pathogens: Modified-Live Versus Inactivated Antigen Vaccines, Intranasal Versus Parenteral, What Is the Evidence?

Vaccination of cattle against viral respiratory pathogens to minimize losses associated with bovine respiratory disease (BRD) is a common practice among producers and veterinarians. Three different calf populations in which BRD is most prevalent (recently weaned beef calves, preweaning beef calves, and young dairy calves) are the principal focus of morbidity and mortality prevention through vaccination; however, the evidence of vaccination efficacy is inconsistent in the literature. This review addresses the evidence of efficacy of vaccination in the prevention or reduction of naturally occurring and experimentally induced BRD in each calf group.

Field trial to evaluate the effect of an intranasal respiratory vaccine protocol on bovine respiratory disease incidence and growth in a commercial calf rearing unit

Background

Bovine respiratory disease (BRD) continues to be great challenge in calf rearing units. The urgent need to decrease the use of antibiotics and increase animal welfare in beef production has forced us to introduce new preventive methods. Vaccinations could contribute to the solution, but the high incidence of BRD already at an early age has made it difficult to introduce suitable vaccination programs. Challenge studies have shown promising results in 3–14 day old calves vaccinated with intranasal BRD vaccine, but very few field trials are available to assess the efficacy of the intranasal vaccines in field conditions. We evaluated the effect of one dose of commercial intranasal vaccination on calf mortality, daily gain, and treatment incidence for BRD in one calf rearing unit. In total, 497 calves (mean age 19 days) were included in our study, 247 of which were vaccinated at the time of arrival to the unit and 250 served as negative controls (unvaccinated). Vaccinated and unvaccinated calves were situated in separate compartments until weaning. Daily gain, treatment incidence, and mortality were recorded until the calves were transported to the finishing unit, which averaged 154.5 days from arrival.

Results

Average daily gain over the complete study period was 1151.9 g/day (SD 137.9) for the vaccinated calves and 1139.5 g/day (SD 135.9) for the unvaccinated calves. Intranasal vaccination combined with older arrival age (17 days or older) resulted in a higher daily gain (47.8 g/day) compared with unvaccinated calves (coef. 0.0478, p = 0.003). This association was not recorded in calves that were younger than 17 days upon arrival. Intranasal vaccination was not significantly associated either with mortality (OR 0.976, p = 0.968) or treatment incidence for BRD (OR 1.341, p = 0.120). In total, six vaccinated calves (2.43%) and six unvaccinated calves (2.40%) died during the study period.

Conclusions

Vaccinating arriving calves with intranasal vaccine in the calf rearing unit did not decrease the mortality or treatment incidence for BRD, but it significantly improved the weight gain in calves transported to the unit at the age of 17 days or older.

Mucosal Vaccine Development for Veterinary and Aquatic Diseases

Because most pathogens and food antigens enter the host via the mucosal surfaces, effective mucosal immunity is critical for maintaining homeostasis through immune regulation, tolerance, and induction of effective immune responses when needed. Thus the mucosa-associated lymphoid tissues represent an important target for vaccination. Indeed, more than 20 years of research have clearly demonstrated the benefits of mucosal vaccination versus systemic vaccination. Such benefits include local induction of secretory immunoglobulin A (SIgA) as well as activation and maturation of mucosal dendritic cells, homing of effector cells to the mucosal surfaces, expression of specific host defense peptides, and other innate effector molecules. In addition, mucosal vaccination offers the opportunity to induce colostral and lactogenic immunity during pregnancy and the possibility of avoiding neutralization of early life vaccines by maternal antibodies, both of which are critical for protecting the most susceptible from infectious diseases. Moreover, mucosal administration offers the advantage of inducing both effective systemic immunity and mucosal immunity, enhancing vaccine efficacy and providing improved protection. A number of animal vaccines are already administered via the mucosal surfaces, with many more to come over the next few years. It is gratifying to see that veterinary vaccine development has yet again taken a leadership role in exploring innovative approaches and technologies to mucosal vaccination. For the veterinary field, considerations for mucosal vaccine development and use necessarily include costs (often pennies per dose), mass delivery that preferably avoids animal restraint, and economic and trade considerations. In this chapter, we provide an overview of some of the existing vaccine technologies and discuss their advantages and disadvantages.

Regional management practices and prevalence of bovine respiratory disease in California's preweaned dairy calves

The objective of this cross-sectional study was to estimate the prevalence of bovine respiratory disease (BRD) in California preweaned dairy calves and identify management practices that are associated with BRD. A convenience sample of 100 dairies in the 3 distinct dairy regions of California was surveyed. Regions evaluated were Northern California (NCA), northern San Joaquin Valley (NSJV), and greater Southern California (GSCA). A questionnaire on calf management practices and demographic information was administered via in-person interviews at each dairy and a random sample of preweaned calves was evaluated using the California BRD scoring system on the same day. Prevalence of BRD varied between the 3 dairy regions: 9.30% in NCA, 4.51% in NSJV, and 7.35% in GSCA. Breed was not associated with BRD prevalence at the statewide level, but differences in prevalence were observed between breeds across the regions with a higher prevalence in NCA for Jerseys and in GSCA for Holsteins, compared with NSJV. Prevalence of BRD was not different between organic and conventional dairies. Colostrum management practices, including heat treatment and feeding colostrum from multiparous cows, varied by region and were associated with lower BRD prevalence. Calves housed in group pens, a practice observed primarily in NCA, had a higher BRD prevalence than those in individual housing. Feeding salable milk was also more common in NCA and was associated with lower BRD prevalence. Ground and road surfaces adjacent to the calf raising area were also variable by region, and paved surfaces were associated with lower BRD prevalence. Management practices associated with BRD varied across the state and may be addressed to inform the adoption and implementation of potentially protective management decisions on California dairies and other regions with similar dairy systems.

Field trial to evaluate the effect of an intranasal respiratory vaccine protocol on calf health, ultrasonographic lung consolidation, and growth in Holstein dairy calves

The objective of this field trial was to evaluate the effect of a vaccine protocol using a commercially available trivalent vaccine designed for intranasal use. Experimental challenge studies have demonstrated varying efficacies of vaccines administered via the intranasal route. A total of 468 calves from 3 herds were enrolled and randomized into 3 treatment groups (positive control, PC, n = 211; intranasal vaccine, IN, n = 215; negative control, NC, n = 42) and followed for 8 to 12 wk. The PC consisted of one dose of commercially available multivalent injectable vaccine against bovine respiratory syncytial virus, infectious bovine rhinotracheitis, parainfluenza 3, and bovine viral diarrhea administered subcutaneously at 6 wk of age. The IN was administered at enrollment and 6 wk of age, and contained antigen against bovine respiratory syncytial virus, infectious bovine rhinotracheitis, and parainfluenza 3. The NC was sterile saline administered intranasally and subcutaneously at enrollment and 6 wk of age. Clinical illness was assessed using systematic respiratory scoring, and thoracic ultrasonography was used to identify the lung consolidation associated with pneumonia. Rib fractures were identified in 6% of calves, and an association was observed between rib fractures and calving ease. Overall, 54% of the calves had at least one episode of an abnormal respiratory score (ILL). Vaccination protocol did not affect the occurrence of ILL. Similarly, 54% of the calves had at least one episode of lung consolidation ≥3 cm (CON). Vaccine protocol affected the odds of CON. The odds of CON in PC were 1.63 (95% confidence interval: 1.04-2.56) times the odds of CON in IN, and 0.38 (95% confidence interval: 0.16-0.93) times the odds of CON in NC. The odds of CON in IN were 0.23 (95% confidence interval: 0.09-0.59) times the odds of CON in NC. The outcomes ILL and CON were associated; however, the measure of agreement was only fair (kappa = 0.38). Multivariable linear regression revealed an interaction between vaccine protocol and herd on average daily gain (ADG); therefore, these data were stratified. In herd 1, IN (0.53 ± 0.03 kg/d) decreased ADG compared with PC (0.63 ± 0.03 kg/d). In herd 2, IN increased ADG (0.41 ± 0.03 kg/d) compared with PC (0.38 ± 0.03 kg/d). In contrast, none of the protocols affected ADG at herd 3. In conclusion, this commercially available trivalent IN vaccine protocol did not alter the incidence of ILL, reduced the risk of lung lesions associated with pneumonia, and improved the ADG of the calves in one of the commercial study herds.

Development and Function of the Mucosal Immune System in the Upper Respiratory Tract of Neonatal Calves

Respiratory infections remain the second most common cause of clinical disease and mortality in newborn calves, which has led to increased interest in using vaccines early in life to mitigate this risk. Intranasal vaccination of neonatal calves can be an effective strategy to circumvent vaccine interference by maternal antibody, but this raises questions regarding onset of immune competence in the upper respiratory tract (URT) following birth. Little is known, however, about the development and function of mucosa-associated lymphoid tissue (MALT) in the URT of newborn calves and what factors, including the commensal microbiome, contribute to this early development. We review the structure, development, and function of MALT in the bovine URT during the first six weeks of life and identify knowledge gaps regarding this early developmental time. This information is critical when designing vaccination programs for young calves, especially when targeting respiratory pathogens that may reside within the commensal microbiome.

Vaccination of calves against common respiratory viruses in the face of maternally derived antibodies(IFOMA)

Vaccination of calves in the face of maternal antibodies (IFOMA) often does not result in seroconversion as maternally derived immunity interferes with the activation of adequate antibody responses to vaccination; however, it can prime T and B cell memory responses that protect calves against clinical disease when maternal immunity has decayed. The activation of B and T cell memory responses in calves vaccinated IFOMA varies and is affected by several factors, including age, level of maternal immunity, type of vaccine, and route of administration. These factors influence the adequate priming of humoral and cell mediated immune responses and the outcome of vaccination. The failure to adequately prime immune memory after vaccination IFOMA could result in lack of clinical protection and increased risk of viremia and/or virus shedding.

BVDV vaccination in North America: risks versus benefits

The control and prevention of bovine viral diarrhea virus (BVDV) infections has provided substantial challenges. Viral genetic variation, persistent infections, and viral tropism for immune cells have complicated disease control strategies. Vaccination has, however, provided an effective tool to prevent acute systemic infections and increase reproductive efficiency through fetal protection. There has been substantial controversy about the safety and efficacy of BVDV vaccines, especially when comparing killed versus modified-live viral (MLV) vaccines. Furthermore, numerous vaccination protocols have been proposed to protect the fetus and ensure maternal antibody transfer to the calf. These issues have been further complicated by reports of immune suppression during natural infections and following vaccination. While killed BVDV vaccines provide the greatest safety, their limited immunogenicity makes multiple vaccinations necessary. In contrast, MLV BVDV vaccines induce a broader range of immune responses with a longer duration of immunity, but require strategic vaccination to minimize potential risks. Vaccination strategies for breeding females and young calves, in the face of maternal antibody, are discussed. With intranasal vaccination of young calves it is possible to avoid maternal antibody interference and induce immune memory that persists for 6-8 months. Thus, with an integrated vaccination protocol for both breeding cows and calves it is possible to maximize disease protection while minimizing vaccine risks.

Commensal microbiome effects on mucosal immune system development in the ruminant gastrointestinal tract

Commensal microflora play many roles within the mammalian gastrointestinal tract (GIT) that benefit host physiology by way of direct or indirect interactions with mucosal surfaces. Commensal flora comprises members across all microbial phyla, although predominantly bacterial, with population dynamics varying with host species, genotype, and environmental factors. Little is known, however, about the complex mechanisms regulating host-commensal interactions that underlie this mutually beneficial relationship and how alterations in the microbiome may influence host development and susceptibility to infection. Research into the gut microbiome has intensified as it becomes increasingly evident that symbiont-host interactions have a significant impact on mucosal immunity and health. Furthermore, evidence that microbial populations vary significantly throughout the GIT suggest that regional differences in the microbiome may also influence immune function within distinct compartments of the GIT. Postpartum colonization of the GIT has been shown to have a direct effect on mucosal immune system development, but information is limited regarding regional effects of the microbiome on the development, activation, and maturation of the mucosal immune system. This review discusses factors influencing the colonization and establishment of the microbiome throughout the GIT of newborn calves and the evidence that regional differences in the microbiome influence mucosal immune system development and maturation. The implications of this complex interaction are also discussed in terms of possible effects on responses to enteric pathogens and vaccines.

The impact of BVDV infection on adaptive immunity

Bovine viral diarrhea virus (BVDV) causes immunosuppression of the adaptive immune response. The level of suppression of the adaptive immune response is strain dependent. The early events of antigen presentation require activation of toll-like receptors that results in the release of pro-inflammatory cytokines. Non-cytopathic (ncp) BVDV infection stimulates cytokines from macrophages in vitro but the effect of BVDV infection in vivo on macrophages or in vitro with monocytes is not clear. Antigen presentation is decreased and co-stimulatory molecules are down regulated. T-lymphocytes numbers are reduced following BVDV infection in a strain dependent manner. There is recruitment of lymphocytes to the bronchial alveolar space following cytopathic (cp) BVDV infection. Depletion of T-lymphocytes occurs in the lymphoid tissue and is strain dependent. BVDV cp T-lymphocyte responses appear to be primarily a T helper 1 response while the response following ncp BVDV induces a T helper 2 response. Cytotoxic T-lymphocytes (CTL), an important BVDV defense mechanism are compromised. The major neutralizing antigens are well characterized but cross-protection between strains is variable. PI animals have normal adaptive immune responses with the exception of the PI strain immunotolerance and mucosal disease may be a function of the level of gamma delta T cells.