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  • Author or Editor: Richard D. Slemons x
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Objective—

To determine whether a commercially available agar gel immunodiffusion test approved for detecting antibodies to Mycobacterium paratuberculosis in cattle could be used for sheep.

Design—

Experimental trial.

Sample Population—

Serum samples from 27 sheep confirmed to have paratuberculosis by means of acid-fast staining of smears of ileal mucosa, histologic examination of tissues, or bacteriologic culture; 7 sheep with clinical signs of paratuberculosis; and 55 sheep from 5 uninfected flocks.

Procedure—

Serum samples were tested concurrently with the commercially available test and with a previously validated agar gel immunodiffusion test. Multiple samples collected from 13 infected sheep over a period of 6 years were also tested so that each test's ability to detect onset of seropositivity could be compared.

Results—

For both tests, results for samples from all 55 uninfected sheep were negative, results for samples from 32 of the 34 sheep with paratuberculosis were positive, and results for the remaining 2 sheep with paratuberculosis were negative. Results of both tests were in agreement for 50 of 54 samples obtained from 13 infected sheep over time. The 4 samples for which results of the 2 tests disagreed were the fourth, eighth, and ninth of 10 samples from 1 sheep and the first of 6 samples from a second sheep. For all 4 samples, the commercially available assay yielded a weak-positive result, but the previously described test yielded a negative result.

Clinical Implications—

The commercially available agar gel immunodiffusion test approved for use in cattle may be useful in the differential diagnosis of paratuberculosis in sheep. (J Am Vet Med Assoc 1996;208:401-403)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To evaluate the potential synergy between bovine respiratory syncytial virus (BRSV) and 3-methylindole (3MI) in inducing respiratory disease in cattle.

Animals

20 mixed-breed beef calves.

Procedure

A 2 × 2 factorial design was used, with random assignment to the following 4 treatment groups: unchallenged control, BRSV challenge exposure (5 × 104 TCID50 by aerosolization and 5.5 × 105 TCID50 by intratracheal inoculation), 3MI challenge exposure (0.1 g/kg of body weight, PO), and combined BRSV-3MI challenge exposure. Clinical examinations were performed daily. Serum 3MI concentrations, WBC counts, PCV, total plasma protein, and fibrinogen concentrations were determined throughout the experiment. Surviving cattle were euthanatized 7 days after challenge exposure. Pulmonary lesions were evaluated at postmortem examination.

Results

Clinical respiratory disease was more acute and severe in cattle in the BRSV-3MI challenge-exposure group than in cattle in the other groups. All 5 cattle in this group and 3 of 5 cattle treated with 3MI alone died or were euthanatized prior to termination of the experiment. Mean lung displacement volume was greatest in the BRSV-3MI challenge-exposure group. Gross and histologic examination revealed that pulmonary lesions were also most severe for cattle in this group.

Conclusions and Clinical Relevance

Feedlot cattle are commonly infected with BRSV, and 3MI is produced by microflora in the rumen of all cattle. Our results suggest that there is a synergy between BRSV and 3MI. Thus, controlling combined exposure may be important in preventing respiratory disease in feedlot cattle. (Am J Vet Res 1999;60:563–570)

Free access
in American Journal of Veterinary Research