Synergistic effects of concurrent challenge with bovine respiratory syncytial virus and 3-methylindole in calves

Howard R. Bingham From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Paul S. Morley From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Thomas E. Wittum From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Tammy M. Bray From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Keith H. West From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Richard D. Slemons From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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John A. Ellis From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Deborah M. Haines From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Mark A. Levy From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Craig F. Sarver From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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William J. A. Saville From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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Victor S. Cortese From the Departments of Veterinary Preventive Medicine (Bingham, Morley, Wittum, Slemons, Saville) and Human Nutrition and Food Management (Bray, Levy), College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210; Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5B4 (West, Ellis, Haines); Ohio Department of Agriculture, 8995 E Main St, Reynoldsburg, OH 43068 (Sarver); and Pfizer Animal Health, 812 Springdale Dr, Whiteland Business Pk, Exton, PA 19341 (Cortese).

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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)

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)

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