EVALUATION OF TWO CANINE DISTEMPER VIRUS VACCINES IN CAPTIVE TIGERS (PANTHERA TIGRIS)

Canine distemper virus (CDV) has caused clinical disease and death in nondomestic felids in both captive settings and in the wild. Outbreaks resulting in high mortality rates in tigers (Panthera tigris) have prompted some zoos to vaccinate tigers for CDV. In this study, six tigers received a recombinant canarypox-vectored CDV vaccine (1 ml s.c.) and were revaccinated with 3 ml s.c. (mean) 39 days later. Blood collection for CDV antibody detection via serum neutralization was performed on (mean) days 0, 26, and 66 post-initial vaccination. No tigers had detectable antibodies at days 0 or 26, and only two tigers had low (16 and 32) antibody titers at day 66. Eight additional tigers received a live, attenuated CDV vaccine (1 ml s.c.) on day 0 and were revaccinated with 1 ml s.c. (mean) 171 days later. Blood collection for CDV antibody detection via serum neutralization was performed on (mean) days 0, 26, 171, and 196. Seven of eight tigers receiving the live, attenuated vaccine had no detectable titers prior to vaccination, but all animals had titers of >128 (range 128-1,024) at day 26. At 171 days, all tigers still had detectable titers (geometric mean 69.8, range 16-256), and at 196 days (2 wk post-revaccination) all but two showed an increase to >128 (range 32-512). To determine safety, an additional 41 tigers were vaccinated with 2 ml of a recombinant vaccine containing only CDV components, and an additional 38 tigers received 1 ml of the live, attenuated vaccine, administered either subcutaneously or intramuscularly; no serious adverse effects were noted. Although both vaccines appear safe, the live, attenuated vaccine produced a stronger and more consistent serologic response in tigers.