Genome-wide association study for response to vaccination in Angus calves1.

BACKGROUND: Bovine respiratory disease complex (BRDC) is one of the most important sources of loss within the beef cattle industry in the USA. Steps have been taken to reduce the incidence of BRDC through vaccination. Despite the effectiveness of vaccines, large proportions of cattle still experience morbidity and mortality. Identification of genomic regions that are associated with variation in response to vaccination would allow for the selection of individuals genetically predisposed to respond to vaccination based on specific markers, while heritability and accuracy estimates would help facilitate genomic selection. This in turn may lead to selection for beef cattle herds that may have lower incidence rate of BRDC after vaccination. This study utilizes an Angus herd of more than 2000 head of cattle to identify these regions of association. RESULTS: Genome wide association studies were performed for viral neutralization antibody level and response to vaccination traits against four different viruses associated with BRDC: bovine viral diarrhea virus 1 and 2 (BVDV1 and BVDV2), bovine respiratory syncytial virus (BRSV), and bovine herpesvirus (BHV1). A total of six 1-Mb windows were associated with greater than 1% of the genetic variance for the analyzed vaccination response traits. Heritabilities ranged from 0.08 to 0.21 and prediction accuracy ranged from 0.01 to 0.33 across 7 different vaccination traits. CONCLUSIONS: Although six 1-Mb windows were identified as associated with 1% or greater genetic variance for viral neutralization antibody level and response to vaccination traits, few genes around these windows could readily be considered candidates. This indicates the need for further functional genomic annotation, as these regions appear to be gene deserts. Traits ranged from lowly to moderately heritable, which indicated the potential for selection of individuals that are genetically pre-disposed to respond to vaccination. The relatively low amount of genetic variance accounted for by any 1-Mb window indicated that viral neutralization antibody level and response to vaccination traits are polygenic in nature. Selection for these traits is possible, but likely to be slow due to the low heritabilities and absence of markers with high genetic variation associated with them.

Effects of injectable trace minerals administered concurrently with a modified live virus vaccine on long-term protection against bovine viral diarrhea virus acute infection in dairy calves.

The objective was to evaluate the effects of injectable trace minerals (ITM) concurrent with modified-live virus (MLV) vaccination on protection from bovine viral diarrhea virus (BVDV) infection in dairy calves. In a previous study (Palomares et al., 2016), thirty dairy calves received two doses of a MLV vaccine subcutaneously (SC), concurrently with ITM (n = 15) or saline (n = 15), SC. Five months later, 20 of these calves received ITM (G1, n = 10) or saline (G2, n = 10) according to their previous groups and were challenged intranasally with BVDV2. Five unvaccinated calves were also challenged with BVDV2 (G3). Blood samples were collected on days 0 (BVDV challenge), 3, 5, 6, 7, 8, 9, 11, 14, 18, 21, 32 and 61 for leukocyte count, virus isolation and BVDV serum neutralizing antibodies (SNA). Mild-moderate clinical signs were observed in G3 after BVDV challenge. Group 1 showed lower sum health score and nasal score on d5 and fecal score on d8 compared to G2. Rectal temperature and leukocyte counts were not different between G1 and G2. In contrast, G3 calves had significant leukopenia and lymphopenia from d3 to d7 (P < .05) and higher rectal temperatures on d6 to d8, compared to values on d0 (P < .05). All unvaccinated calves became viremic, while viremia was not detected in G1 or G2. Average daily gain was not different between vaccinated groups, however, only G1 calves had significantly greater (P = .04) ADG compared to non-vaccinated calves during the first 14 days post challenge. Vaccinated calves treated or not with ITM were protected from BVDV2 infection five months post-vaccination.

Agreement Among 4 Sampling Methods to Identify Respiratory Pathogens in Dairy Calves with Acute Bovine Respiratory Disease.

BACKGROUND: Four sampling techniques commonly are used for antemortem identification of pathogens from cattle with bovine respiratory disease (BRD): the nasal swab (NS), guarded nasopharyngeal swab (NPS), bronchoalveolar lavage (BAL), and transtracheal wash (TTW). Agreement among these methods has not been well characterized. OBJECTIVE: To evaluate agreement among TTW and NS, NPS, or BAL for identification of viral and bacterial pathogens in dairy calves with BRD. ANIMALS: One hundred dairy calves with naturally acquired BRD. METHODS: Calves were sampled by all 4 methods. Viral agents were identified by real-time RT-PCR, bacteria were identified by aerobic culture, and Mycoplasma bovis (M. bovis) isolates were speciated by PCR. Agreement among TTW and NS, NPS, or BAL was evaluated by calculating the kappa statistic and percent positive agreement. McNemar's exact test was used to compare the proportions of positive results. RESULTS: Agreement among TTW and NS, TTW and NPS, and TTW and BAL, was very good for identification of P. multocida, M. haemolytica, and M. bovis. For bovine respiratory syncytial virus (BRSV), agreement with TTW was moderate for NS, good for NPS, and very good for BAL. For bovine coronavirus (BCV), agreement with TTW was moderate for NS and NPS, and good for BAL. McNemar's test was significant only for BCV, indicating that for this pathogen the proportion of positive results from NS and NPS could not be considered comparable to TTW. CONCLUSIONS AND CLINICAL IMPORTANCE: This study provides guidance for veterinarians selecting diagnostic tests for antemortem identification of pathogens associated with BRD.

Evaluation of responses to vaccination of Angus cattle for four viruses that contribute to bovine respiratory disease complex.

Although vaccination is an effective measure in reducing the risk of bovine respiratory disease complex (BRDC) in cattle, BRDC losses remain significant. Increasing the efficacy of vaccination depends on elucidating the protective immune response to different antigens included in vaccines, determining the best timing for vaccination, and understanding the impact of the age of the calf on vaccination. This study measured the serum antibodies present in calves following vaccination against 4 viruses commonly associated with BRDC: bovine viral diarrhea virus type 1 and 2 (BVDV1 and BVDV2), bovine respiratory syncytial virus (BRSV), and bovine herpesvirus 1 (BHV1). Serum antibody titers were measured in more than 1,600 calves at 3-wk intervals starting at the time of the first vaccination. This first vaccination occurred at weaning for approximately half of the individuals and 3 wk before weaning for the other half. Dam age (years), time of weaning (initial vaccination or booster vaccination), and age of calf within year-season (days within year-season) classification all were found to have a significant effect on measured traits such as the initial titer and overall response. An increased initial titer was negatively correlated with each response trait (initial, booster, and overall response). Calves that were weaned at initial vaccination had greater overall antibody response to BVDV1 and BVDV2 compared with calves weaned 3 wk before initial vaccination. In contrast, calves given their initial vaccination 3 wk before weaning had greater overall antibody response to BRSV and BHV1 compared with calves that were vaccinated at weaning. Furthermore, the circulating antibody titer at which each virus needed to be below for an individual calf to positively respond to vaccination was determined (log titer of 0.38 for BVDV1, 1.5 for BVDV2, 3.88 for BRSV, and 1.5 for BHV1). This information can be used to improve vaccination protocols to allow for a greater response rate of individuals to vaccination and, hopefully, improved protection.

Effects of injectable trace minerals on humoral and cell-mediated immune responses to Bovine viral diarrhea virus, Bovine herpes virus 1 and Bovine respiratory syncytial virus following administration of a modified-live virus vaccine in dairy calves.

Our objective was to evaluate the effect of an injectable trace mineral (ITM) supplement containing zinc, manganese, selenium, and copper on the humoral and cell mediated immune (CMI) responses to vaccine antigens in dairy calves receiving a modified-live viral (MLV) vaccine containing BVDV, BHV1, PI3V and BRSV. A total of 30 dairy calves (3.5 months of age) were administered a priming dose of the MLV vaccine containing BHV1, BVDV1 & 2, BRSV, PI3V, and an attenuated-live Mannheimia-Pasteurella bacterin subcutaneously (SQ). Calves were randomly assigned to 1 of 2 groups: (1) administration of ITM SQ (ITM, n=15) or (2) injection of sterile saline SQ (Control; n=15). Three weeks later, calves received a booster of the same vaccine combination SQ, and a second administration of ITM, or sterile saline, according to the treatment group. Blood samples were collected on days 0, 7, 14, 21, 28, 42, 56, and 90 post-vaccination for determination of antibody titer, viral recall antigen-induced IFN-γ production, and viral antigen-induced proliferation by peripheral blood mononuclear cells (PBMC). Administration of ITM concurrently with MLV vaccination resulted in higher antibody titers to BVDV1 on day 28 after priming vaccination compared to the control group (P=0.03). Calves treated with ITM showed an earlier enhancement in PBMC proliferation to BVDV1 following vaccination compared to the control group. Proliferation of PBMC after BVDV stimulation tended to be higher on day 14 after priming vaccination in calves treated with ITM than in the control group (P=0.08). Calves that received ITM showed higher PBMC proliferation to BRSV stimulation on day 7 after priming vaccination compared to the control group (P=0.01). Moreover, calves in the ITM group also had an enhanced production IFN-γ by PBMC after stimulation with BRSV on day 21 after priming vaccination compared to day 0 (P<0.01). In conclusion, administration of ITM concurrently with MLV vaccination in dairy calves resulted in increased antibody titer to BVDV1, and greater PBMC proliferation to BVDV1 and BRSV recall stimulation compared to the control group, suggesting that ITM might represent a promising tool to enhance the humoral and CMI responses to MLV vaccines in cattle.

Prevalence of bacteremia in dairy cattle with acute puerperal metritis.

BACKGROUND: Acute puerperal metritis (APM) affects 30% of postpartum dairy cattle. Bacteremia negatively impacts survival in cattle with coliform mastitis. However, the prevalence of bacteremia in dairy cattle with APM is unknown. HYPOTHESIS: Bacteremia is detectable in a large proportion of cattle with APM. ANIMALS: Seventeen dairy cows with APM and 17 healthy dairy cattle. METHODS: Prospective case-control study. Cases were identified by daily monitoring of cattle in the first 10 days after calving. Controls were matched to cases by parity and days in milk. Cows were examined at the time of identification of APM. A complete blood count, serum biochemical analysis, and bacteriologic culture of blood and lochial fluid were performed on each animal at the time of diagnosis. The same samples were collected from healthy herdmates of a similar parity and days in milk. Blood culture results and clinicopathologic variables were compared between groups. Conditional logistic regression was used to evaluate factors associated with APM, whereas multivariate logistic regression was used to evaluate factors associated with bacteremia. RESULTS: Bacteremia occurred in 53% (9/17) of cattle with APM and 53% (8/15) controls. Bacillus spp. was the organism most commonly isolated from the bloodstream in cattle of both groups. Bacteremic cattle in both groups were significantly less likely to have basophils in the peripheral circulation (P = .02) and more likely to have higher serum globulin concentrations (P = .02). CONCLUSIONS AND CLINICAL IMPORTANCE: Bacteremia is a common occurrence in postpartum dairy cattle. Further study is warranted to investigate the modes by which bacteria colonize the bloodstream in this population of animals and the importance of bacteremia on health and productivity of affected animals.

Comparative efficacy of enrofloxacin and tulathromycin for treatment of preweaning respiratory disease in dairy heifers.

Preweaning respiratory disease continues to have a substantial effect on the current and future productivity of dairy replacement animals. Establishing an effective treatment plan for the preweaned calf may have a significant effect on well-being and lifetime productivity by limiting any early development of chronic disease. The primary objective of this study was to examine the efficacy of treatment with tulathromycin (TUL) or enrofloxacin (ENR) on the risk of re-treatment, with a secondary objective of investigating the effect of disease and subsequent treatment choice on average daily gain (ADG). A total of 1,141 Holstein heifers from 4 farms were observed and systematically scored for evidence of respiratory disease from birth through weaning or the time of death. At the time of diagnosis, calves were randomly and blindly allocated into 2 treatment groups. The overall incidence of respiratory disease was 60.9%. In the univariable analysis, the incidence of re-treatment between 7 and 10d of initial therapy for calves treated with ENR was greater than that in calves treated with TUL (27.6 vs. 21.2%). After adjusting for farm ID, clinical score at first treatment, and weight at first treatment, the odds of re-treatment were 1.5 times higher for calves treated with ENR than with TUL. The percentage of calves that required more than one re-treatment was higher for calves that received ENR compared with those that received TUL (9.3 vs. 4.1%). We observed no difference in ADG between calves treated with ENR or TUL, and no difference in ADG between calves that were treated for respiratory disease and those that were not treated for respiratory disease. Appropriate drug therapy for preweaning respiratory disease may have an important role in reducing the odds of re-treatment during the preweaning period.

The relationship between serum calcium concentration and outcome in horses with renal failure presented to referral hospitals.

BACKGROUND: Hypercalcemia is common in horses with renal failure, but it is not known whether it impacts prognosis. HYPOTHESIS/OBJECTIVES: The primary objective of this study was to determine whether hypercalcemia was associated with decreased likelihood of survival to discharge in horses with renal failure. Secondary objectives were to determine whether hypercalcemia was more common in acute (ARF) or chronic renal failure (CRF), whether feeding alfalfa was associated with hypercalcemia, and whether serum creatinine concentration was associated with survival. ANIMALS: Medical records of 63 horses presented to referral hospitals for renal failure were evaluated. Cases were classified as ARF or CRF based on historical and clinical findings. METHODS: The distribution of hypocalcemic, normocalcemic, and hypercalcemic cases in the ARF and CRF groups was determined. Mean serum calcium and creatinine concentrations for survivors and nonsurvivors, and for ARF and CRF cases, were compared. Mean serum calcium concentrations for cases fed alfalfa or not fed alfalfa were compared. RESULTS: Hypercalcemia was significantly more common in CRF than ARF cases. CRF cases fed alfalfa were significantly more likely to be hypercalcemic. There was no significant difference in serum calcium concentration between survivors and nonsurvivors. Serum creatinine concentration was significantly higher in nonsurvivors and in ARF cases. CONCLUSIONS AND CLINICAL IMPORTANCE: Horses with CRF are more likely to be hypercalcemic than horses with ARF. Hypercalcemia was not associated with outcome in renal failure cases in this study. Additional research on the impact of dietary calcium on long-term well-being in horses with CRF is warranted.

Mycoplasma bovis infections in cattle.

Mycoplasma bovis is a pathogen causing respiratory disease, otitis media, arthritis, mastitis, and a variety of other diseases in cattle worldwide. It is increasingly recognized by the veterinary and livestock communities as having an important impact on the health, welfare, and productivity of dairy and beef cattle. M. bovis diseases can be difficult to diagnose and control because of inconsistent disease expression and response to treatments and vaccines, and large gaps in our understanding of the epidemiology and pathophysiology of these diseases. There are limited data on which to base evidence-based decisions for treatment and control, and the literature contains differing clinical biases and opinions. This document is intended for veterinarians dealing with cattle and is focused on the cattle production systems of North America. The goal of the consensus statement panel was to encourage an evidence-based approach to M. bovis problems. The scientific literature was critically reviewed, including peer-reviewed journal articles and reviews obtained by database searches using the terms "Mycoplasma bovis" or "mycoplasma + cattle." Where other data were lacking, conference proceedings were reviewed as a source of expert opinion.

Pathogenesis of a bovine enterovirus-1 isolate in experimentally infected calves.

The pathogenesis and virulence of Bovine enterovirus-1 (BEV-1) in cattle is largely unknown. Reports concerning its virulence suggest that there might be an association between BEV-1 infections and a range of diseases in cattle that vary from respiratory to enteric to reproductive disease and infertility. In the current study, the pathogenesis associated with acute infection of BEV-1 in calves experimentally inoculated with the Oklahoma isolate of BEV-1 was described. Although interpretation of the study was limited by lack of an effective control group, results suggest that an association between inoculation of BEV-1, virus localization, and the potential development of lesions in the brain and heart probably exists. In the experiment, BEV-1 virus localized to the terminal ileum, ileocecal and cecocolonic junctions, spiral colon, and ileocecal lymph nodes; BEV-1 virus was detected in the cytoplasm of enterocytes, lamina propria macrophages, endothelium, neurons of the submucosal and myenteric plexi, and lymphocytes of the submucosal lymphoid tissue. Although no clinical signs were noted following acute infection, BEV-1 was localized in the cerebellar white matter of a calf with encephalitis and in the heart of another calf with coronary arteritis. The current study suggests that the BEV-1 isolate is infectious to young calves and that BEV-1 potentially can have a similar pathogenesis to that observed in natural or experimental enterovirus infections in other species.

The effect of various Mycoplasma bovis isolates on bovine leukocyte responses.

Mycoplasma bovis (M. bovis) contributes to a number of clinical syndromes in cattle; in particular, chronic pneumonia that is poorly responsive to therapy has been increasingly recognized as an important cause of morbidity, mortality, and financial loss. M. bovis impairs host immune function, but little is known about whether field isolates vary significantly in their effect on immune function. This research tested the hypothesis that different field isolates vary in their ability to suppress cellular metabolism and cellular production of radical oxygen species (ROS) by bovine leukocytes. Total blood leukocytes from 6 cattle were exposed to six field isolates, two diagnostic lab isolates, and two high passage laboratory isolates of M. bovis, and ROS production was measured by oxidation of dihydrorhodamine 123 (DHR-123). Cellular metabolism was measured by reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Significant differences in the response to some field isolates were identified. Three field isolates and both diagnostic lab isolates significantly decreased ROS production by leukocytes from multiple cattle, while the high pass laboratory isolates did not. In contrast, MTT reduction was not significantly impaired by any of the M. bovis strains tested. M. bovis impairs ROS production by bovine leukocytes; the magnitude of the effect appears to be isolate-dependent, and is not related to a general impairment of cellular metabolism. Chronic M. bovis infection in some cattle may be related to impaired ability of leukocytes to produce ROS when exposed to M. bovis.

Evaluation of multiple immune parameters after vaccination with modified live or killed bovine viral diarrhea virus vaccines.

The development of immunity to vaccine antigen was examined using three prime/boost strategies and the progression of immune activities was evaluated over the course of 8 weeks. Calves were vaccinated and multiple immune parameters were evaluated using several methods to assess humoral or cellular immunity from the same samples in parallel. The three vaccination protocols used were a killed vaccine followed by a killed boost (killed/killed), MLV vaccine and boost (MLV/MLV), or a MLV vaccine and killed boost (MLV/killed). All the vaccines used included modified live IBR/PI3 viruses to make the bystander context as similar as possible. The Singer strain of BVDV was used as the source antigen in the killed vaccine, and the NADL strain of BVDV was used in the MLV vaccine. Controls received a vaccine containing only MLV IBR/PI3. The assessment panel measured SN titers, as well as lymphocyte proliferation, cytokine mRNA expression, intracellular cytokine production, and released IFN-gamma after in vitro stimulation with three strains of BVDV virus. MLV/MLV and MLV/killed groups developed significant SN titers to the type 1 BVDV virus strains, Singer and NADL, and low crossover titers were also seen to the type 2 strain, 890 over the evaluation period. These two groups showed significant proliferation in response to the NADL virus as compared to controls. Multiple immune assessments were conducted simultaneously to attempt to provide a broader, more in depth evaluation of immune response to these BVDV vaccination protocols. We observed that the correlation among most of the assays conducted were weak; the correlation between SN titers and cellular proliferation assays demonstrated a moderate correlation.

Bovine respiratory syncytial virus-specific IgE is associated with interleukin-2 and -4, and interferon-gamma expression in pulmonary lymph of experimentally infected calves.

OBJECTIVE: To study the local immune response of calves to bovine respiratory syncytial virus (BRSV) infection with emphasis on IgE production and cytokine gene expression in pulmonary lymph. ANIMALS: Twelve 6- to 8-week-old Holstein bull calves. Six similar control calves were mock infected to obtain control data. PROCEDURE: Lymphatic cannulation surgery was performed on 12 calves to create a long-term thoracic lymph fistula draining to the exterior. Cannulated calves were exposed to virulent BRSV by aerosol. Lymph fluid collected daily was assayed for BRSV and isotype-specific IgE antibody, total IgG, IgA, IgM, and protein concentrations. Interleukin-4 (IL-4), interleukin-2 (IL-2), and interferon-gamma were semi-quantitated by reverse transcription-polymerase chain reaction (RT-PCR). Cell counts and fluorescence-activated cell scanner (FACSCAN) analysis of T-cell subsets were performed on lymph cells. RESULTS: Calves had clinical signs of respiratory tract disease during days 5 to 10 after infection and shed virus. Bovine respiratory syncytial virus-specific IgE in infected calves was significantly increased over baseline on day 9 after infection. Mean virus-specific IgE concentrations strongly correlated with increases in severity of clinical disease (r = 0.903). Expression of IL-2, IL-4, and interferon-gamma was variably present in infected and control calves, with IL-4 expression most consistent during early infection. CONCLUSIONS AND CLINICAL RELEVANCE: Infection with BRSV was associated with production of BRSV-specific IgE, and IL-4 message was commonly found in lymph cells of infected calves. This finding supports the concept that BRSV-induced pathophysiology involves a T helper cell type-2 response. Effective therapeutic and prophylactic strategies could, therefore, be developed using immunomodulation to shift the immune response more toward a T helper cell type-1 response.

Evaluation of severe disease induced by aerosol inoculation of calves with bovine respiratory syncytial virus.

OBJECTIVE: To develop a model of bovine respiratory syncytial virus (BRSV) infection that induces severe disease similar to that seen in some cattle with naturally acquired BRSV infection. ANIMALS: 25 male Holstein calves, 8 to 16 weeks old. PROCEDURE: 17 calves were given a low-passage field isolate of BRSV by aerosolization; 8 control calves were given supernatant from noninfected cell culture. Disease was characterized by evaluating clinical signs, virus isolation and pulmonary function tests, and results of blood gas analysis, gross and histologic postmortem examination, and microbiologic testing. RESULTS: Cumulative incidence of cough, harsh lung sounds, adventitious sounds, and dyspnea and increases in rectal temperature and respiratory rate were significantly greater in infected calves. Three infected calves developed extreme respiratory distress and were euthanatized 7 days after inoculation. Virus was isolated from nasal swab specimens from all infected calves but not from mock infected calves. On day 7 after inoculation, mean PaO2 and PaCO2 were significantly lower, and pulmonary resistance was significantly higher, in infected calves. During necropsy, infected calves had varying degrees of necrotizing and proliferative bronchiolitis and alveolitis with syncytial formation. The 3 calves euthanatized on day 7 had emphysematous bullae in the caudal lung lobes; 1 had unilateral pneumothorax. CONCLUSION AND CLINICAL RELEVANCE: Severe disease similar to that seen in some cattle with naturally acquired BRSV infection can be induced in calves with a single aerosol exposure of a low-passage clinical isolate of BRSV. Our model will be useful for studying the pathogenesis of BRSV infection and for evaluating vaccines and therapeutics.

Interferon gamma production during bovine respiratory syncytial virus (BRSV) infection is diminished in calves vaccinated with formalin-inactivated BRSV.

Formalin-inactivated respiratory syncytial virus (FI-RSV) vaccination has been associated with severe disease in humans. Research in mice suggests that FI-RSV may prime for decreased interferon gamma (IFN-gamma) production at subsequent infection. Interferon-gamma production by peripheral blood mononuclear cells (PBMC) was measured following challenge of calves vaccinated with FI-BRSV to determine whether a similar mechanism is operative in a host naturally susceptible to RSV. Eight-week old male Holstein calves were administered FI-BRSV and mock challenge (V/M, n = 6); mock vaccination and BRSV challenge (M/C, n = 6) or FI-BRSV and BRSV challenge (V/C, n = 7). Vaccine was administered twice at a 2-week interval; challenge followed one month later. On days 0, 5 and 10 postchallenge (PC), PBMC were stimulated in vitro for 24 h with live BRSV, concanavalin A (positive control) or spent media (negative control). Supernatants were assayed for IFN-gamma using ELISA. Interferon-gamma production by BRSV-stimulated PBMC was increased in M/C and V/C calves as compared to V/M calves on day 5 PC (p < 0.015); and increased in M/C calves compared to V/C and V/M calves on day 10 PC (p < 0.015). Over time postchallenge, a significant increase in IFN-gamma production by BRSV-stimulated PBMC was seen in M/C calves (p < 0.025) but not in V/C calves. FI-BRSV vaccination of calves led to diminished IFN-gamma production postchallenge. Decreased IFN-gamma production may have contributed to impaired viral clearance and enhanced disease in FI-BRSV vaccinated calves.

A bovine model of vaccine enhanced respiratory syncytial virus pathophysiology.

A critical issue has been the observation that vaccination of children with a formalin-inactivated respiratory syncytial virus (RSV) vaccine is associated with disease enhancement. We have taken advantage of bovine RSV and our experience with this disease in calves to develop a natural model that parallels human disease. Using formalin-inactivated bovine RSV vaccine calves were either sham-vaccinated/infected, vaccinated/infected, or vaccinated/sham-infected and their clinical signs, pulmonary function, and histological lung lesions quantitatively scored. Interestingly there was significantly greater disease in vaccinated/infected calves and histological lesions in calves were similar to those of affected children. Finally, we note that vaccination did not induce neutralizing antibodies, but IgG antibodies were detected by ELISA. Our model of RSV enhanced disease is important because it provides quantifiable evidence of disease severity that can be applied to evaluate the mechanisms of immunopathology and the safety of candidate RSV vaccines.

Aortic and iliac artery thrombosis in calves: nine cases (1974-1993).

OBJECTIVE: To identify common clinical and diagnostic features of calves with aortic or iliac artery thrombosis that might aid in antemortem diagnosis of this condition. DESIGN: Retrospective case series. ANIMALS: 9 calves < or = 6 months old in which aortic or iliac artery thrombosis was confirmed at necropsy. RESULTS: All calves had an acute onset of paresis or flaccid paralysis of 1 or both hind limbs. Affected limbs were hypothermic and had diminished spinal reflexes and diminished pulse pressures. Diagnosis was definitively established in 2 calves by use of angiography. All 9 calves died or were euthanatized. CLINICAL IMPLICATIONS: This condition is rare and could be mistaken for more common diseases of young cattle, such as traumatic injury of the axial or appendicular skeleton, vertebral osteomyelitis, nutritional muscular dystrophy associated with vitamin E or selenium deficiency, injury to the sciatic or femoral nerves, or clostridial myositis.