Corticosteroid treatment does not reactivate canine herpesvirus in red foxes

To study canine herpesvirus (CHV) reactivation from red foxes (Vulpes vulpes), 29 foxes with varying CHV antibody and CHV carrier status were treated with methylprednisolone acetate, a glucocorticosteroid drug with prolonged immunosuppressive effect in dogs. In the first experiment, 17 foxes with unknown CHV carrier status were treated once with methylprednisolone: in the second experiment, five foxes were treated twice, 4 mo after being intravenously CHV infected; and in the third experiment, six foxes were treated five times, 11 mo after peroral CHV infection. Infectious CHV was not isolated after treatment from either naturally or experimentally CHV-infected foxes or from untreated, CHV-seronegative in-contact foxes. Canine herpesvirus DNA was not detectable in mucosal secretions or white blood cells of any of the foxes, whereas all trigeminal ganglia of experimentally CHV-infected foxes were polymerase chain reaction-positive. In CHV-seropositive foxes, anti-CHV antibody titers did not change with time after treatment, and CHV-seronegative in-contact controls did not seroconvert. Hematologic parameters remained mostly unchanged. We conclude that CHV is not as easily reactivated in foxes following corticosteroid treatment as in dogs, although there was no obvious sign of immunosuppression. Canine herpesvirus was not spread from virus carriers to naive in-contact foxes, which may be among possible explanations for the reported low CHV prevalence in wild foxes.