Immunization of pups with maternal derived antibodies against canine parvovirus, using an intranasally administered modified live canine parvovirus type 2b vaccine [Immunizzazione di cuccioli con anticorpi materni nei confronti del parvovirus del cane con vaccino vivo modificato CPV-2b per via intranasale]

The purpose of this study was to evaluate the ability of a modified live (ML) canine parvovirus (CPV) type 2b vaccine, to elicit active immunization in pups with maternally derived antibodies (MDA) by intranasal administration. Seventy-eight 5 to 7-week-old pups were used from 16 litters born to bitches that had been vaccinated with a commercially-available ML CPV-2 vaccine, before mating. Pups were vaccinated initially when they were 5 weeks old. If they failed to seroconvert, they were revaccinated at the age of 7 weeks. The vaccine induced active seroconversion in all the pups with MDA of <= 80, as well as in 66.6% and 37.5% of pups with MDA titers respectively of 160 and 320. None of the pups with MDA titers >= 640 sero-converted after vaccination. Sequence analysis in the ORF2, revealed several amino acid changes in the capsid protein VP2, between the ML CPV-2b virus used in this study and commercially-available type-2 vaccine viruses. The high efficacy of the ML-CPV-2b vaccine in overcoming the MDA obstacle may be accounted for by either the antigenic/biological differences between CPV-2 and the variants 2a/b, or a better induction of active immunization obtainable administering the vaccine by the nasal route.