Immunocompetent and
cyclophosphamide-immunosuppressed ferrets were intranasally infected with canine
parainfluenza virus (CPIV) and observed for clinical signs, histopathologic lesions, the immunocytochemical demonstration of CPIV
antigen in the respiratory tract and scanning electron microscopic alterations of the tracheal epithelium until 36 days post
infection (p.i.). In both groups, clinical signs were minimal, restricted to the upper respiratory tract and consisted of
cough elicited by tracheal compression between 3 and 7 days p.i. Microscopically, inflammatory and degenerative lesions were observed in the trachea and less frequently in the nasal cavity;
bronchiolitis or
interstitial pneumonia was not demonstrated. By immunocytochemistry, CPIV
antigen was demonstrated in tracheal epithelial cells, whereas nasal cavity, bronchi, bronchioles and lung were devoid of
viral antigen. Ferrets given CPIV alone developed a minimal lymphocytic
tracheitis with minimal loss of cilia and CPIV
antigen was observed only 4 days p.i. 17 days p.i., normal epithelial organization and ciliary reappearance was reestablished. Ferrets treated with
cyclophosphamide and infected with CPIV exhibited mild to moderate histological lesions as above with similar scanning electron microscopic changes until 36 p.i. Tracheal lesions consisted of intraepithelial and submucosal infiltration of lymphocytes and macrophages,
focal epithelial hyperplasia and multifocal loss of cilia. In addition, mild and transient neutrophilic infiltration was observed. In immunosuppressed ferrets,
viral antigen expression was prominent and demonstrated 4 and 8 days p.i. These data suggest that ferrets are susceptible to
aerosol CPIV
infection.