The role of phagocytic cells in enhanced susceptibility of broilers to colibacillosis after Infectious Bronchitis Virus infection

Colibacillosis results from infection with avian pathogenic Escherichia coli bacteria. Healthy broilers are resistant to inhaled E. coli, but previous infection with vaccine or virulent strains of Infectious Bronchitis Virus (IBV) predisposes birds for severe colibacillosis. We investigated whether IBV affects recruitment and function of phagocytic cells and examined NO production, phagocytic and bactericidal activity, and kinetics of peripheral blood mononuclear cells (PBMC) and splenocytes. Moreover, we measured cytokine mRNA expression in lung and spleen samples. Broilers were inoculated with IBV H120 vaccine or virulent M41 and challenged 5 days later with E. coli 506. A PBS control and E. coli group without previous virus inoculation were also included. Birds were sacrificed at various time points after inoculation (h/dpi). Inoculation with IBV induced extended and more severe colibacillosis than with E. coli alone. At 4dpi, the number of KUL-01(+) PBMC in all E. coli-inoculated groups was significantly higher than in PBS-inoculated birds, which correlated with lesion scores. From 1 to 4dpi, NO production by PBMC from all E. coli-inoculated animals was elevated compared to PBS birds. Bactericidal activity of PBMC in IBV-inoculated animals at 7dpi was lower than in PBS- and E. coli-inoculated birds, but phagocytic capacity and recruitment were not severely impaired. In spleen samples of IBV-infected animals reduced expression of IL-1beta, IL-6, IL-8, IL-10, IL-18 and IFN-gamma mRNA was found 1dpi. Our results suggest that enhanced colibacillosis after IBV infection or vaccination is caused at least by altered innate immunity and less by impairment of phagocytic cell function.     

Cellular immune response cytokine expression during the initial stage of bovine leukemia virus (BLV) infection determines the disease progression to persistent lymphocytosis

We have established experimental models of bovine leukemia virus (BLV) infection followed by progression to persistent lymphocytosis (PL) positive (BLV+PL+) or PL negative (BLV+PL-) stages of infection. Two out of six BLV infected animals developed PL+ 4 weeks after BLV infection. One other animal became PL+ late in the course of infection and three infected animals stayed PL-. These animals (PL-) exhibited transient lymphocytosis 3-4 weeks after infection and sustained PL- lymphocyte counts up to 24 weeks after infection. Competitive RT-PCR analysis of IFN-gamma mRNA expression revealed that peripheral blood mononuclear cells (PBMC) of animals with PL+ status developed by 4 weeks after infection had augmented IFN-gamma mRNA expression 3-4 weeks after BLV infection. However PBMC of animals that sustained a long-termed PL- lymphocyte count had elevated IFN-gamma mRNA expression 1-24 weeks after infection. Competitive RT-PCR analysis of IL-2 mRNA expression showed an increase in the levels of IL-2 mRNA in PL animals. Interleukin-10 (IL-10) mRNAs expression were elevated both in PL+ and PL- animals from 3 and 12 weeks after infection respectively. We suggest that early and extended expression of cellular response cytokines may delay the progression to PL+ in enzootic bovine leukemia.     

Analysis of the antigen-specific IFN-gamma producing T-cell subsets in cattle experimentally infected with Mycobacterium bovis

Three 10 months old cattle were infected by the intratracheal route with 10(6)cfu of a field strain of Mycobacterium bovis. Blood samples were regularly collected for in vitro IFN-gamma production after antigenic stimulation. Peripheral blood cells of infected animals produced IFN-gamma in response to crude M. bovis antigens (live and heat-inactivated BCG and protein-purified derivative (PPD)) 3-4 weeks after infection. The ratio of the response to bovine PPD versus avian PPD indicated a specific sensitisation for M. bovis antigens. Three months post-infection (PI), animals were culled and M. bovis was cultured from tubercle lesions. At different time points, the frequency of specific M. bovis IFN-gamma producing CD4+, CD8+ and WC1+ T-cells in the peripheral blood was examined by flow cytometry. Two colour immunofluorescence staining of intracellular IFN-gamma and bovine cell surface molecules showed that both CD4+ and CD8+, but not WC1+, T-cells produced IFN-gamma following stimulation with PPD, live or killed BCG.In two animals analysed, the relative percentage of circulating IFN-gamma producing CD8+ cells decreased between week 5 and week 9 PI. The same evolution was not observed for IFN-gamma secreting CD4+ cells. Magnetic positive selection of T-cells from infected animals showed that CD4+ T-cells produced specific IFN-gamma only in the presence of antigen presenting cells (APCs). Positively selected CD8+ T-cells secreted IFN-gamma only in the presence of recombinant human IL-2 and APCs. In vitro depletion of the CD4+ T-cells, but not the depletion of CD8+ or WC1+ T-cells, resulted in abrogation of the specific IFN-gamma production showing the key role of this cell population for the specific IFN-gamma production.     

Interferon-gamma and interleukin-4 expression during Fasciola gigantica primary infection in crossbred bovine calves as determined by real -time PCR

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) expression in crossbred (Bos taurusxBos indicus) bovine calves during primary infection with Fasciola gigantica was measured. Ten crossbred calves of 1-year age were divided into two groups of five calves each, group I uninfected control and group II calves orally infected with a dose of 1000 metacercariae of F. gigantica. The two cytokines were measured 10, 30 and 75 days post-infection (PI) by real-time polymerase chain reaction (RT-PCR) with the double stranded DNA-binding dye SYBR Green. IL-4 was present in detectable levels in peripheral blood mononuclear cells (PBMCs) of infected animals at 10, 30 and 75 days PI but no IFN-gamma was detected in PBMCs of infected animals at 10 and 30 days PI. However, at 75 days PI, IFN-gamma in two infected animals was present in detectable level. Eosinophil count increased from 2nd fortnight after infection and the increased level persisted till the termination of experiment. Present study indicated that T-cell response during F. gigantica infection was Th2-type during earlier phase of infection, which may be polarized in chronic infection to that of a Th0-type.     

Comparative genomics and proteomics to study tissue-specific response and function in natural Mycobacterium bovis infections

Bovine tuberculosis (bTB) is an established zoonotic disease which affects cattle and wildlife worldwide and new strategies are required to control and eradicate the disease. The European wild boar (Sus scrofa) is a major reservoir of bTB in Spain. The objective of this paper was to review tissue-specific response and function of mandibular lymph nodes (MLN) and oropharyngeal tonsils (OT) in European wild boar naturally infected with Mycobacterium bovis. Genomics and proteomics data were used to compare differential gene expression and global protein patterns in OT and MLN of M. bovis-infected and uninfected European wild boar and the results were analyzed considering previous reports of experimental infections in laboratory and domestic animals. The results showed tissue-specific differences in OT and MLN in response to M. bovis infection. Tissue-specific differences in gene expression and protein profiles suggested different functions for OT and MLN during mycobacterial infection and provided information to characterize the pathobiology of M. bovis infection in European wild boar with important implications for the control of bTB in Spain. The characterization of molecular events in tissues that play different roles during mycobacterial infection in naturally infected individuals may be relevant to understand the pathobiology of M. bovis infection and to design effective strategies for the control of bTB in wildlife reservoirs.     

Quantitative analysis of inflammatory and immune responses in dogs with gastritis and their relationship to Helicobacter spp. infection

The present study sought to quantitatively examine mucosal inflammatory and immune responses in dogs with gastritis and the relationship of these responses to infection with Helicobacter. Gastric biopsies from 30 dogs were evaluated for B- and T-lymphocytes, neutrophils, eosinophils, macrophages, and mast cells. Mucosal atrophy, fibrosis, cellularity, and severity of gastritis were graded qualitatively. Messenger-RNA (mRNA) for actin, interleukin-1beta (IL-1beta), IL-4, IL-8, and IL-10, transforming growth factor beta (TGF-beta), and interferon gamma (IFN-gamma) was quantified by polymerase chain reaction (PCR). The presence of Helicobacter spp. was determined by urease activity, histology, PCR, and enzyme-linked immunosorbent assay. mRNA for IL-1beta, IL-8, IL-10, TGF-beta, and IFN-gamma was detected in most dogs. IL-4 mRNA was detected in only 1 dog. Correlations were observed for IL-1beta versus IL-8 and IL-10; IL-8 versus IL-10, IFN-gamma, and TGF-beta; and IL-10 versus IFN-y. Mucosal pathology was related to cytokine mRNA expression (neutrophils to IL-8 and IFN-gamma, macrophages and lymphocytes to IFN-gamma, and fibrosis to IL-1beta). Gastritis was categorized as lymphoplasmacytic in all dogs, and its histologic severity correlated with atrophy, infiltration with lymphocytes and macrophages, and expression of IL-10 and IFN-gamma. Of the dogs examined, 76.7% were infected with Helicobacter spp. Infection was associated with increased expression of TGF-beta and fibrosis. Circulating anti-Helicobacter immunoglobulin G titers were higher in uninfected than infected dogs. We conclude that lymphoplasmacytic gastritis in dogs is characterized by concurrent activation of proinflammatory and immunomodulatory cytokines, with increased mRNA expression related to mucosal pathology. No significant associations between Helicobacter infection and proinflammatory cytokine expression, severity of gastritis, or differences in the pathogenicity of different Helicobacter spp. were found.     

Differential expression of inducible nitric oxide synthase and cytokine mRNA in chicken lines divergent for cutaneous hypersensitivity response

Phytohemagglutinin (PHA)-induced delayed-type hypersensitivity is an immunocompetent trait considered an indicator of cell-mediated immune or T-cell responses. Divergent selection was performed to generate high and low lines for response to PHA-P. Extreme-responder birds of the F2 generation in each line were used to study possible differences in macrophage activity and the associated functional genes. To evaluate macrophage activity, nitric oxide (NO) was estimated both systemically in serum and in in vitro monocyte culture. Semi-quantitative RT-PCR was used to detect the differential mRNA expression patterns of iNOS and MIP-1beta in monocyte culture, whereas T(H)1 cytokines (IL-2 and IFN-gamma) were studied in peripheral blood mononuclear cells (PBMC) at different time intervals after lipopolysaccharide (LPS) induction. The high line showed strong systemic, as well as in vitro NO production, compared to the low line, upon stimulation with NDV and LPS, similar to early and high iNOS mRNA expression. Following the pattern of iNOS gene expression, an early strong expression of cytokines with powerful iNOS-inducing action, such as IFN-gamma and the chemokine MIP-1beta, was observed in the high line. In contrast, for response to PHA-P, low expression of IL-2 was observed in the high compared to the low line. In conclusion, the study revealed that divergent selection for response to PHA-P resulted in a divergent effect on T(H)1 cell activity, resulting in altered macrophage function in chickens. Selection, based on response to PHA-P, could lead to more resistant birds or birds with an enhanced immune response.     

Antiviral effect of Saccharomyces cerevisiae beta-glucan to swine influenza virus by increased production of interferon-gamma and nitric oxide

The aim of these experiments was to investigate the potential antiviral effect of Saccharomyces cerevisiae beta-glucan on the pneumonia induced by swine influenza virus (SIV). Forty colostrum-deprived 5-day-old piglets were randomly divided into four groups of 10. The 20 pigs in groups 1 and 2 were administered Saccharomyces cerevisiae beta-glucan orally (50 mg/day/pig; En-Bio Technology Co., Ltd) for 3 days before SIV infection and those in groups 3 and 4 were given culture medium/diluent alone. Groups 1 and 3 were inoculated intranasally with 3 ml of tissue culture fluid containing 2 x 10(6) tissue culture infective doses 50% (TCID(50))/ml of SIV and those in groups 2 and 4 were exposed in the same manner to uninfected cell culture supernatant. The microscopic lung lesions induced by SIV infection (group 1 pigs) were significantly more severe than those induced by infection in animals pre-administered beta-glucan (group 3) (P < 0.05). Significantly more SIV nucleic acid was detected in the lungs of pigs experimentally infected with SIV only (group 1) at 5, 7 and 10 days post-inoculation (dpi) compared with lungs from pigs pre-administered beta-glucan and infected with SIV (group 3) (P < 0.05). The concentrations of interferon-gamma (IFN-gamma) and nitric oxide (NO) in bronchoalveolar lavage fluid from pigs pre-administered beta-glucan and infected with SIV (group 3) were significantly higher than for any other group at 7 and 10 dpi for IFN-gamma, and at 5, 7 and 10 dpi for NO (P < 0.05). Saccharomyces cerevisiae beta-glucan reduced the pulmonary lesion score and viral replication rate in SIV-infected pigs. These findings support the potential application of beta-glucan as prophylactic/treatment agent in influenza virus infection.     

Lymphocyte subset proliferative responses of Mycobacterium bovis-infected cattle to purified protein derivative

Despite highly successful eradication efforts in several countries, Mycobacterium bovis infection of cattle remains a significant health concern worldwide. Immune mechanisms of resistance to and/or clearance of M. bovis infection of cattle, however, are unclear. Recent studies have provided evidence supporting a role for CD4(+), CD8(+), and gammadelta TCR(+) T cells in the response of cattle to M. bovis. In the present study, we utilized a flow cytometric-based proliferation assay to determine the relative contribution of individual lymphocyte subsets in the response to M. bovis infection and/or sensitization with mycobacterial purified protein derivative (PPD). Peripheral blood mononuclear cells (PBMC) from M. bovis-infected cattle proliferated in response to in vitro stimulation with M. bovis PPD. CD4(+) T cells and gammadelta TCR(+) cells were the predominate subsets of lymphocytes responding to PPD. gammadelta TCR(+) cells also proliferated in non-stimulated cultures; however, the gammadelta TCR(+) cell proliferative response of infected cattle was significantly (p<0.05) greater in PPD-stimulated cultures as compared to non-stimulated cultures. Intradermal injection of PPD for comparative cervical testing (CCT) induced a boost in the in vitro proliferative response of CD4(+) but not gammadelta TCR(+) cells of infected cattle. Administration of PPD for CCT also boosted interferon-gamma (IFN-gamma) production by PBMC of infected cattle following in vitro stimulation with M. bovis PPD. Injection of PPD for CCT did not, however, elicit a proliferative or IFN-gamma response in cells isolated from non-infected cattle. These data indicate that CD4(+) and gammadelta TCR(+) cells of M. bovis-infected cattle proliferate in a recall response to M. bovis PPD and that the CD4(+) cell response is boosted by intradermal injection with PPD for CCT.     

Alteration in lymphocyte responses,cytokine and chemokine profiles in chickens infected with genotype VII and VIII velogenic Newcastle disease virus

Newcastle disease (ND) is a highly contagious avian disease and one of the major causes of economic losses in the poultry industry. The emergence of virulent NDV genotypes and repeated outbreaks of NDV in vaccinated chickens have raised the need for fundamental studies on the virus–host interactions. In this study, the profiles of B and T lymphocytes and macrophages and differential expression of 26 immune-related genes in the spleen of specific-pathogen-free (SPF) chickens, infected with either the velogenic genotype VII NDV strain IBS002 or the genotype VIII NDV strain AF2240, were evaluated. A significant reduction in T lymphocyte population and an increase in the infiltration of IgM⁺ B cells and KUL01⁺ macrophages were detected in the infected spleens at 1, 3 and 4 days post-infection (dpi) (P < 0.05). The gene expression profiles showed an up-regulation of CCLi3, CXCLi1, CXCLi2 (IL-8), IFN-γ, IL-12α, IL-18, IL-1β, IL-6, iNOS, TLR7, MHCI, IL-17F and TNFSF13B (P < 0.05). However, these two genotypes showed different cytokine expression patterns and viral load. IBS002 showed higher viral load than AF2240 in spleen at 3 and 4 dpi and caused a more rapid up-regulation of CXCLi2, IFN-γ, IL-12α, IL-18, IL-1β, iNOS and IL-10 at 3 dpi. Meanwhile, the expression levels of CCLI3, CXCLi1, IFN-γ, IL-12α, IL-1β and iNOS genes were significantly higher in AF2240 at 4 dpi. In addition, the expression levels of IL-10 were significantly higher in the IBS002-infected chickens at 3 and 4 dpi. Hence, infection with velogenic genotype VII and VIII NDV induced different viral load and production of cytokines and chemokines associated with inflammatory reactions.     

Shedding of Mycobacterium bovis in the nasal mucus of cattle infected experimentally with tuberculosis by the intranasal and intratracheal routes

Four groups of six calves were infected experimentally with either a low dose of approximately 10(4) colony-forming units (cfu) or a high dose of approximately 10(6) cfu of Mycobacterium bovis. Each dose was delivered by the intranasal and intratracheal routes. More severe disease was observed in the groups inoculated with the high dose. Visible lesions were identified in 21 of the 24 animals, all of which also gave positive skin tests and interferon-gamma (IFN-gamma) responses. Nasal shedding was detected in 15 of the 24 animals and the frequency of shedding was influenced by both the route and the dose of infection; no shedding was observed in the group infected intratracheally with the low dose. Two of the 15 confirmed shedders had no visible lesions at postmortem examination; both of these calves gave IFN-gamma responses but only one was skin test positive.     

Evaluation of an in vitro blood-based assay to detect production of interferon-gamma by Mycobacterium bovis-infected white-tailed deer (Odocoileus virginianus).

Tuberculosis due to Mycobacterium bovis in captive Cervidae was identified as an important disease in the United States in 1990 and prompted the addition of captive Cervidae to the USDA Uniform Methods and Rules for eradication of bovine tuberculosis. As well, M. bovis infection was identified in free-ranging white-tailed deer in northeast Michigan in 1995. Tuberculosis in both captive and free-ranging Cervidae represents a serious challenge to the eradication of M. bovis infection from the United States. Currently, the only approved antemortem tests for tuberculosis in Cervidae are the intradermal tuberculin skin test and the blood tuberculosis test (BTB). At present, the BTB is not available in North America. Tuberculin skin testing of Cervidae is time-consuming and involves repeated animal handling and risk of injury to animals and humans. This study evaluated the potential of a new blood-based assay for tuberculosis in Cervidae that would decrease animal handling, stress, and losses due to injury. In addition, a blood-based assay could provide a more rapid diagnosis. Twenty 6-9-month-old white-tailed deer, male and female, were experimentally inoculated by instillation of 300 colony-forming units of M. bovis in the tonsillar crypts. Seven, age-matched uninfected deer served as controls. Blood was collected on days 90, 126, 158, 180, 210, 238, 263, and 307 after inoculation and was analyzed for the production of interferon-gamma (IFN-gamma) in response to incubation with M. bovis purified protein derivative (PPDb), M. avium PPDa, pokeweed mitogen (PWM), or media alone. Production of IFN-gamma in response to PPDb was significantly greater (P < 0.05) at all time points in samples from M. bovis-infected deer as compared with uninfected control deer, whereas IFN-gamma production to PWM did not differ significantly between infected and control deer. Measurement of IFN-gamma production to PPDb may serve as a useful assay for the antemortem diagnosis of tuberculosis in Cervidae.     

Augmentation of secreted and intracellular gamma interferon following johnin purified protein derivative sensitization of cows naturally infected with Mycobacterium avium subsp. paratuberculosis.

Measurement of secreted interferon (IFN)-gamma has proven to be a valuable tool for the detection of animals infected with mycobacterial pathogens, including Mycobacterium avium subsp. paratuberculosis. Previous reports have suggested that tuberculin skin testing can influence the performance of the IFN-gamma assay. In the present study, healthy noninfected cows, and cows subclinically and clinically infected with M. paratuberculosis were administered an intradermal injection of johnin purified protein derivative (JPPD) and effects on secreted and intracellular IFN-gamma were observed. Intradermal injection resulted in significant increases in secreted IFN-gamma for subclinically infected cows after stimulation of peripheral blood mononuclear cells (PBMC) with concanavalin A or M. paratuberculosis antigen preparations (whole-cell sonicate and JPPD) on days 7 and 10 postinjection. Intracellular IFN-gamma was increased after intradermal injection in total PBMC for all treatment groups and was higher within CD4+ and CD8+ subpopulations for infected cows compared to healthy controls throughout the study. When T-cell populations were further defined by CD45RO expression, intracellular IFN-gamma was higher within CD8+/CD45RO+ lymphocytes compared to CD4+/CD45RO+ cells for subclinically and clinically infected cows but similar within these subpopulations for healthy controls. These results indicate that intradermal sensitization of cows in the subclinical stage of infection will upregulate expression of IFN-gamma, enhancing the sensitivity of this assay. In addition, CD8+ lymphocytes appear to play an important role as a mediator of M. paratuberculosis infection in naturally exposed cattle.     

IL-4 and IL-10 inhibition of IFN-gamma- and TNF-alpha-dependent nitric oxide production from bovine mononuclear phagocytes exposed to Babesia bovis merozoites.

The requirement for IFN-gamma and/or TNF-alpha as co-stimulants with Babesia bovis merozoites for nitric oxide (NO) production was examined, as well as the regulatory role of IL-4 and IL-10. Purified B. bovis merozoites did not induce the production of NO in undifferentiated monocytes without addition of exogenous IFN-gamma and TNF-alpha unless the monocytes taken ex vivo were producing TNF-alpha endogenously. Under the latter condition, the NO production resulting from merozoite stimulation remained IFN-gamma-dependent. There was no evidence for endogenous synthesis of TNF-alpha in monocyte-derived macrophages (MDM), and merozoites alone were incapable of inducing TNF-alpha mRNA in MDM. However, while merozoites plus IFN-gamma induced TNF-alpha mRNA expression in MDM, NO was not produced. Both IL-4 and IL-10 inhibited expression of iNOS and production of NO in merozoite-stimulated monocytes.     

Pathological and immunological changes after challenge infection with Pasteurella multocida in naive and immunized calves

Challenge infections of calves with Pasteurella multocida were established to characterize the local inflammatory response and determine the effect of previous exposure to live bacteria on the post-challenge immune response. Experimental infections were established by intratracheal inoculation of P. multocida in both naive calves and calves that had been previously vaccinated with two subcutaneous (s.c.) injections of live bacteria. Histological, immunohistological and cytokine expression studies were performed on bronchoalveolar lavage (BAL) samples, lung parenchymal tissues and lung lymph nodes (LN). In comparison to uninfected control animals in which no lung lesions were observed, a patchy to confluent bronchopneumonia was observed following infection of naive calves, characterized by abscess formation, haemorrhage, oedema and suppurative consolidation. Cellular analysis following infection of naive animals was characterized by an influx of neutrophils in the BAL, with macrophages and dendritic cells observed in the lesion perimeter. A significant increase in the number of CD8(+) blasts expressing MHC (major histocompatibility) II was also observed in the BAL of infected calves. Decreased expression of interleukin (IL)-1 beta and increased expression of IL-8 compared to naive unchallenged controls was apparent in lung LN. In comparison, a more limited pathology was observed in vaccinated animals post-challenge, indicating partial protection conferred by the s.c. immunization with live bacteria. Studies of vaccinated animals showed the presence of bronchial-associated lymphoid tissue (BALT) in the lung tissue and an increase in the number of B-cells and CD4(+) T-cells expressing MHCII in the lung LN after challenge. In contrast to primary infection, there was no significant influx of neutrophils in the BAL. Instead, a population of newly recruited monocytes/macrophages was observed. Increased IL-2 expression and decreased IL-8 expression was observed in the LN, while IL-1 beta expression was not detected. The reduced neutrophil and increase monocyte response in the vaccinated calves may be associated with significant changes in the gamma delta T lymphocyte population in the BAL.     

Secretion of IFN-gamma by bovine peripheral blood mononuclear cells stimulated with Mycobacterium bovis protein fractions obtained by isoelectric-focusing

Due to the complexity and variety of biological effects found in Mycobacterium bovis (M. bovis) proteins analyzed solely on a molecular weight (MW) basis, we approached the purification of M. bovis proteins through their isoelectric point (pI). Twenty M. bovis culture filtrate protein extract (CFPE) isoelectric focused (IEF) protein fractions, confined between pI3 and 10, were isolated. The MW of the major proteins isolated in the various fractions correlated with protein already reported 14-, 18-, 20-, 25-, 31-, 38-, 45-, 64-, 67- and 70 kDa by SDS-PAGE. Since several different pI fractions showed proteins of the same MW we tested the ability of all IEF fractions to stimulate interferon-gamma (IFN-gamma) production by peripheral blood mononuclear cells (PBMC) isolated from cattle with well defined M. bovis tuberculosis (TB) infection. In animals with few lesions IFN-gamma inductive IEF fractions were in the acid range. As the number of lesions increased, neutral fractions were also inductive. Some fractions with relatively few proteins induced as much IFN-gamma production as others with abundant proteins. None of the 20 IEF fractions enhanced IFN-gamma production by anergic cells. We conclude that IFN-gamma production in diseased animals is induced mainly by acidic mycobacterial proteins and that the response towards these proteins is enhanced as the disease progresses, what coincides with higher PPD reactivity. However, the IFN-gamma production in anergic status was severely affected. We found that this cytokine production is spontaneous and antigen-independent.     

The efficacy of valnemulin (Econor) in the control of disease caused by experimental infection of calves with Mycoplasma bovis

Mycoplasma bovis infection was experimentally induced in groups of six young calves. A further group was uninfected and served as a control. Ten days after infection, medication with either enrofloxacin (Baytril, Bayer) or valnemulin (Econor, Novartis) was instituted via the milk replacer for a further 10 days, after which all calves were killed. Infection resulted in depression, pyrexia, inappetance and prominent respiratory signs. Arthritis occurred in two animals and two (unmedicated) animals died. At post-mortem examination extensive lesions were present in the lungs and M. bovis was re-isolated from infected unmedicated calves' lungs. Medication with either enrofloxacin or valnemulin resulted in a rapid diminution of clinical signs, restoration of appetite and reversal of weight loss. Isolation of Pasteurella multocida from the calves' lungs was suppressed by both medicaments. Valnemulin resulted in a more rapid reduction of clinical scores and eliminated M. bovis from the lungs more effectively than enrofloxacin.     

Investigation of the transmission of Mycobacterium bovis from deer to cattle through indirect contact

OBJECTIVE: To investigate the infection of calves with Mycobacterium bovis through oral exposure and transmission of M. bovis from experimentally infected white-tailed deer to uninfected cattle through indirect contact. ANIMALS: 24 11-month-old, white-tailed deer and 28 6-month-old, crossbred calves. PROCEDURE: In the oral exposure experiment, doses of 4.3 x 10(6) CFUs (high dose) or 5 x 10(3) CFUs (low dose) of M. bovis were each administered orally to 4 calves; as positive controls, 2 calves received M. bovis (1.7 x 10(5) CFUs) via tonsillar instillation. Calves were euthanatized and examined 133 days after exposure. Deer-to-cattle transmission was assessed in 2 phases (involving 9 uninfected calves and 12 deer each); deer were inoculated with 4 x 10(5) CFUs (phase I) or 7 x 10(5) CFUs (phase II) of M. Bovis. Calves and deer exchanged pens (phase I; 90 days' duration) or calves received uneaten feed from deer pens (phase II; 140 days' duration) daily. At completion, animals were euthanatized and tissues were collected for bacteriologic culture and histologic examination. RESULTS: In the low- and high-dose groups, 3 of 4 calves and 1 of 4 calves developed tuberculosis, respectively. In phases I and II, 9 of 9 calves and 4 of 9 calves developed tuberculosis, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that experimentally infected deer can transmit M. bovis to cattle through sharing of feed. In areas where tuberculosis is endemic in free-ranging white-tailed deer, management practices to prevent access of wildlife to feed intended for livestock should be implemented.