The avian origin canine influenza virus H3N2 has been recently isolated and found to be currently in dog population in South Korea and China. The purpose of this study was to clarify the relationship between immunosuppressive glucocorticoids used in veterinary clinical practice and viral shedding pattern of influenza in dogs.

Eight conventional beagle dogs were divided into control infection group and immunocompromised group. Dogs of both groups were infected with H3N2 canine influenza virus (2×10^6.0 EID₅₀/0.1 mL). Dogs in immunocompromised group were given orally 3.0 mg/kg prednisolone for 7 days. Virus shedding was monitored using real-time polymerase chain reaction. After necropsy, histopathologic lesions were compared.

We found that immunocompromised dogs exhibited more prolonged (8 days vs. 13 days) and higher magnitude viral shedding than control group (peak titer of viral shedding 4.6 vs. 5.5 EID₅₀).

Restricted use of immunosuppressive drugs in the clinical setting might help control the rapid spread of H3N2 through local dog populations.