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Microbiologic findings in feedlot cattle with acute interstitial pneumonia

Amelia R. WoolumsDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Gary L. MasonVeterinary Diagnostic Laboratory, College of Veterinary Medicine, Colorado State University, Fort Collins, CO 80523.

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Larry L. HawkinsDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
Present address is Bayer HealthCare LLC, PO Box 390, Shawnee, KS 62727.

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Corrie C. BrownDepartment of Veterinary Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Shamita M. WilliamsDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Jared A. GouldDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Jocelyn J. FoxDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Scott D. SturgeonDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Jenny L. AndersonDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Florence E. DugganDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Susan SanchezAthens Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Paula B. BarrettAthens Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Sharon W. ChitwoodAthens Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Abstract

Objective—To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP.

Animals—39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens.

Procedure—Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically.

Results—Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection.

Conclusions and Clinical Relevance—Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem. (Am J Vet Res 2004;65:1525–1532)

Abstract

Objective—To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP.

Animals—39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens.

Procedure—Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically.

Results—Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection.

Conclusions and Clinical Relevance—Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem. (Am J Vet Res 2004;65:1525–1532)