A modified-live intranasal (IN) canine
parainfluenza (
CPI)-virus Bordetella bronchiseptica
vaccine was evaluated in dogs for efficacy against laboratory-induced canine infectious tracheobronchitis. The comparative efficacies of IN and parenteral administrations of the
CPI virus fraction were also evaluated. The frequency and duration of clinical tracheobronchitis, blood serum agglutination titer, humoral antibody response, and duration of
CPI virus and B bronchiseptica shedding were measured. Group A dogs were vaccinated subcutaneously or IM with an experimental
CPI vaccine and challenge exposed with
CPI virus. Group B dogs were vaccinated IN with avirulent
CPI virus-B bronchiseptica live
antigens and challenge exposed with virulent
CPI virus and virulent B bronchiseptica. The IN vaccination (group B) significantly reduced (P less than or equal to 0.001) the occurrence of clinical tracheobronchitis by 96%. The combined challenge exposure of virulent
CPI and virulent B bronchiseptica produced a synergistic enhancement of the clinical signs of kennel
cough. The percentage of days after challenge exposure that virus shedding was detected for controls equaled 70% as compared with 50% and only 1% for parenterally and IN vaccinated dogs, respectively. Isolation of virulent B bronchiseptica microorganisms was reduced 89% in dogs vaccinated IN compared to controls. The geometric mean humoral antibody titers to
CPI virus after 2 parenteral vaccinations and 1 IN vaccination were 1:43 and 1:34, respectively.