Clinicopathologic analysis of herpesvirus-induced urinary tract infection in specific-pathogen-free cats given methylprednisolone

The clinicopathologic manifestations of bovid herpesvirus-4 (BHV-4; FCAHV strain)-induced infection of the lower portion of the urinary tract were characterized in 12 adult neutered male and 6 female specific-pathogen-free cats, and were compared with those in 12 neutered male control cats. Six neutered male and 6 female cats were given immunosuppressive doses of methylprednisolone acetate prior to inoculation of their urinary bladders with BHV-4. Six neutered male control cats were given immunosuppressive doses of methylprednisolone acetate prior to inoculation of their urinary bladders with uninfected tissue culture control inoculum. Six additional neutered male control cats were exposed only to uninfected tissue culture control inoculum. All cats were observed for 90 days following inoculation. Dysuria and gross hematuria were observed in only 1 BHV-4-exposed cat. Radiographic abnormalities of the lower portion of the urinary tract were not observed. Microscopic hematuria, crystalluria, and lipiduria were identified with similar frequency in BHV-4-exposed and control cats. Results of urine culturing for bacteria, mycoplasma, ureaplasma, and viruses were negative. Viruses were not isolated from blood leukocytes collected from exposed or control cats. Three to 6 weeks after inoculation, high concentrations of BHV-serum 4 antibodies were detected in all exposed cats by an indirect fluorescent antibody test. Light microscopic examination of the urinary tract revealed multifocal lymphoid cystitis in 2 BHV-4-exposed cats. Except for suppurative bronchitis in 1 BHV-4-exposed cat given glucocorticoids, morphologic differences in urinary and extraurinary tissues were not observed. In urinary bladder tissue collected 90 days after inoculation, BHV-4 was reisolated from urinary bladder explants of all but 1 exposed cat. Virus was also isolated from a kidney explant of 1 exposed male cat, and spleen cell cocultures of 1 exposed female cat given glucocorticoids. Bovid herpesvirus-4 (FCAHV strain) caused persistent urinary tract infections in male and female specific-pathogen-free cats. Detection of occult BHV-4 infection required isolation of virus from tissues by explantation, or demonstration of specific BHV-4 antibodies by immunofluorescent fluorescent techniques. Administration of glucocorticoids prior to inoculation did not enhance morbidity associated with BHV-4 urinary tract infection. Further investigations are needed to determine the pathogenic role of BHV-4 in 4 noninduced feline lower urinary tract disease.