Protection of dogs against canine distemper by vaccination with a canarypox virus recombinant expressing canine distemper virus fusion and hemagglutinin glycoproteins.
A canary pox virus recombinant-canine distemper virus (CDV) combination vaccine was tested for safety and efficacy along with other modified-live virus (MLV) components (canine adenovirus type 2, canine coronavirus, canine parainfluenza virus and canine parvovirus) in 26 SPF, 7- to 10-week-old Beagle pups. The combination vaccine was rehydrated with either Leptospira canicola-L icterohaemorrhagiae combination bacterin (vaccine 1) or sterile diluent (vaccine 2). An additional group of 7 seronegative SPF pups received the control MLV components without the combination vaccine (vaccine 3). Two vaccinations were administered 21 days apart, either i.m. or s.c. The dose of the combination vaccine used to inoculate these pups was 40 times lower than the recommended commercial dose. All pups were challenged with a virulent CDV strain 21 days after the booster vaccination and were observed for a further 21 days. No adverse effects were induced by the vaccinations. All vaccinates seroconverted to CDV. Serum antibody titres to MLV components were not different, with or without inclusion of the combination vaccine. After challenge exposure, morbidity and mortality were 0% in vaccinates and 100 and 86% (6/7), respectively, in control dogs. Brain impression smear slides made from all dogs that did not survive challenge exposure were positive to CDV by the direct fluorescein isothiocyanate method. It is concluded that the canary pox virus-CDV combination vaccine, administered s.c. or i.m., is safe, elicits CDV seroconversion and protects vaccinated pups against virulent CDV challenge exposure.