Bovine coronavirus in the lower respiratory tract of cattle with respiratory disease

Abstract

Bovine coronavirus (BCoV) is a known cause of enteric disease in cattle; however, its role in bovine respiratory disease (BRD) is poorly understood, with a dearth of evidence of the detection of the virus in respiratory tract lesions. We coupled histologic evaluation of tracheal and lower airway tissues from 104 calves with BRD in which BCoV was detected in the lungs via PCR followed by direct detection of BCoV by immunohistochemistry and an RNA in situ hybridization assay (ISH; RNAscope technology). RNAscope ISH detected BCoV in respiratory epithelium in more cases than did IHC. Using both methods of direct detection, tracheal epithelial attenuation and identification of the virus within lesions were observed commonly. Our results confirm a role of BCoV in respiratory tract infection and pathology, and show that the virus likely plays a role in the development of BRD.

Keywords: RNAscope; bovine coronavirus; histopathology; immunohistochemistry; respiratory disease.

Figures 1–5.

Bovine coronavirus (BCoV) in the lung of cattle with respiratory disease. Figure 1. Multifocal, intracytoplasmic immunolabeling within bronchial epithelium. Immunohistochemistry (IHC). Figures 2, 3. Detection of BCoV by IHC (Fig. 2) and in situ hybridization (ISH; Fig. 3) in sloughed epithelium within the lumens of bronchi. Figure 4. Intraluminal detection of BCoV nucleic acid (arrows) within cells in an artery. ISH. Figure 5. Strong ISH labeling of intra-alveolar cellular debris.

Figures 6–10.

Bovine coronavirus (BCoV) in the trachea of cattle with respiratory disease. Figure 6. Tracheitis with submucosal congestion, and degeneration and necrosis of tracheal epithelium (enlarged in inset). H&E. Figure 7. Denudation of tracheal mucosa and intraluminal sloughing with mononuclear infiltrates within the submucosa. H&E. Figure 8. Immunolabeling of tracheal epithelium for BCoV antigen. Immunohistochemistry. Figure 9. Strong labeling of BCoV nucleic acid in tracheal epithelium. In situ hybridization (ISH). Figure 10. Scattered labeling of nucleic acid within the lamina propria (arrowheads). ISH.