Abstract

Canine distemper virus (CDV) is a significant threat to domestic and wildlife carnivore species worldwide. Vaccinations against CDV are routinely administered to wildlife species in captive and rehabilitative settings and are being more commonly used in free-ranging carnivores as a conservation tool. Because CDV is a major cause of mortality in gray foxes (Urocyon cinereoargenteus), we evaluated the safety and immunogenicity of a commercial canine multivalent vaccine that included canarypoxvirus recombinant CDV and modified live (MLV) canine parvovirus type-2 (CPV2) components for use in gray foxes. Six, healthy 2-wk-old gray fox kits were admitted to the Kentucky Wildlife Center in April 2014. Five kits negative for maternal antibodies to CDV were vaccinated 4 times (on admission and every 3 wk) subcutaneously (Recombitek®C3, Merial, Inc., Athens, GA, USA). One served as a contact control, receiving injections of sterile diluent. None of the kits exhibited any adverse local or systemic reactions, and all remained clinically healthy throughout the trial. Although there was variability among individuals, all five kits seroconverted by serum neutralization after the first vaccination. Peak titer levels were not reached until after the third vaccination. The control remained seronegative throughout the first phase and was then vaccinated. Because all titers dropped after the fourth vaccination, a booster was administered to all six foxes in November 2014. An increase in titer was noted for all foxes. Our study showed that the multivalent vaccine was safe in gray foxes even when given as young as 2 wk of age. Titer levels peaked after the third vaccination, suggesting that foxes may benefit from additional boosters in the rehabilitation setting due to high risk of infection. To provide additional protection, it might be advantageous to administer an additional dose prior to release, especially since newly released foxes could come into contact with potential CDV hosts during home range establishment.