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  • Author or Editor: Timothy W. J. Olchowy x
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Summary

Antibody titer to Ehrlichia risticii was determined, in 2,549 equine serum samples, using an indirect fluorescent antibody assay. During 1986, samples were obtained from the Minnesota State-Federal Equine Infectious Anemia Diagnostic Laboratory, the Minnesota Racing Laboratory, from horses admitted to the University of Minnesota Veterinary Teaching Hospital, and as a result of field investigations of horses with acute diarrhea. Results of the study revealed antibody prevalence of 33, 24, 47, and 25% for the respective groups. There was no statistical association between seropositive status and age, sex, breed, or clinical problem of horses referred to the teaching hospital. There was an increase in the total percentage of seropositive samples over the duration of the sample collection period, suggesting a seasonal exposure pattern, and E risticii was associated with clinical and subclinical infections in horses of Minnesota.

Free access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the efficacy of difloxacin, a novel fluoroquinolone antibiotic, in calves experimentally infected with Mannheimia haemolytica (formerly Pasteurella haemolytica).

Animals—Seventy-two 3-month-old Holstein calves.

Procedures—Calves were inoculated with M haemolytica intratracheally; after they developed clinical signs of pneumonic pasteurellosis, they were randomly assigned to 1 of 6 groups (n = 12/group). Calves in each group were treated with 10% difloxacin (2.5 or 5 mg/kg of body weight), 5% difloxacin (2.5 or 5 mg/kg), enrofloxacin (5 mg/kg), or saline (0.9% NaCl) solution (control group), once daily for 5 days, and clinical signs were scored daily. On day 15, calves were euthanatized, and the percentage of diseased lung tissue was calculated. Swab specimens of the lungs were submitted for bacterial culture.

Results—Mortality rate and percentage of diseased lung tissue were significantly higher and cure rate and average daily gain were significantly lower for control calves, compared with calves in the treatment groups; however, no significant differences were found among treatment groups. Mannheimia haemolytica was isolated from the lungs of 10 control calves and from at least 2 calves in each of the treatment groups.

Conclusions and Clinical Relevance—Results suggest that difloxacin and enrofloxacin were equally effective for treatment of calves with experimentally induced pneumonic pasteurellosis. However, treatment of infected calves with difloxacin or enrofloxacin may not eliminate the organism. (Am J Vet Res 2000;61:710–713)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To investigate the effects of anti-inflammatory drugs on lipopolysaccharide-induced procoagulant activity of bovine alveolar macrophages.

Design

Procoagulant activity was induced in bovine alveolar macrophages from 4 healthy Holstein calves aged 6 to 16 weeks by incubation with lipopolysaccharide. 3 anti-inflammatory drugs were used at 4 concentrations and 3 times to pretreat the alveolar macrophages. Results were analyzed to determine whether drug, concentration, or exposure period had a significant (P> 0.05) effect.

Procedure

Bovine alveolar macrophages, harvested by volume-controlled bronchoalveolar lavage, were pretreated for 30, 60, or 120 minutes with an anti-inflammatory compound (dexamethasone, flunixin meglumin, or phenylbutazone) at several concentrations (0, 1, 10, and 100 μM). Bovine alveolar macrophages were exposed to lipopolysaccharide (Escherichia coli O55:B5) in the presence and absence of fetal bovine serum for 4 hours. Procoagulant activity was measured, using a chromogenic assay.

Results

None of the drugs was associated with a modification of procoagulant activity expression.

Conclusion

Use of these 3 anti-inflammatory drugs is unlikely to modify the extent of the fibrinous reaction commonly observed in cases of acute bovine respiratory tract disease complex.

Clinical Relevance

The alveolar macrophage has a key role in fibrin production. Assuming in vivo events mimic the in vitro model, is appears unlikely that administration of anti-inflammatory drugs will reduce the procoagulant activity of the bovine alveolar macrophages and the directly associated pulmonary fibrosis. (Am J Vet Res 1996; 57:659–663)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate receptor-mediated intracellular events in bovine alveolar macrophages (AM) stimulated by bacterial lipopolysaccharide (LPS), using tissue factor (TF) expression as the measurable functional endpoint.

Sample Population

Pulmonary AM harvested from 1- to 4-month-old male Holstein calves.

Procedure

Alveolar macrophages, acquired by use of volume-controlled bronchopulmonary lavage, were treated with CD14 monoclonal antibody (20 μg/ml), pertussis toxin (300 ng/ml), or 1 of 3 known protein kinase C (PKC) inhibitors (10 μM chelerythrin, 100 μM H-7, or 50 nM staurosporin), then were stimulated with LPS alone (0.01, 0.10, 1.0, 10.0 μg/ml) or LPS (0.25, 0.5, 1.0 ng/ml) in combination with concentrated bovine serum fraction 2 (500 ng/ml). Tissue factor expression was quantified by use of a colorimetric assay. Changes in intracellular Ca2+ concentration and pH were monitored, using Ca2+- and pH-sensitive fluorescent dyes, with changes in fluorescent intensity after incubation with LPS measured by spectrophotometry.

Results

Treatment of AM with a CD14 monoclonal antibody caused profound inhibition of TF expression (P < 0.0001) after stimulation by LPS combined with bovine serum fraction 2. Pertussis toxin had a significant (P < 0.0319) inhibitory effect on TF expression when cells were stimulated by LPS alone. Treatment with all 3 PKC inhibitors caused marked reduction in TF expression of cells stimulated with LPS alone or with phorbol myristate acetate. Stimulation of cells by LPS failed to mobilize intracellular Ca2+ stores or to alter cytosolic pH.

Conclusion

LPS combined with serum factors binds to CD14 on the surface of AM, and PKC is an important signaling kinase in the pathway utilized by LPS, resulting in enhanced TF expression; a pertussis toxin-sensitive G protein is involved in the signaling pathway utilized by LPS alone; and mobilization of Ca2+ does not have a role in the signal transduction pathway utilized by LPS nor does LPS affect cytosolic pH of AM. (Am J Vet Res 1998;59:445–451)

Free access
in American Journal of Veterinary Research