VACCINATION OF BLACK-FOOTED FERRET (MUSTELA-NIGRIPES) X SIBERIAN POLECAT (MUSTELA-EVERSMANNI) HYBRIDS AND DOMESTIC FERRETS (MUSTELA-PUTORIUS-URO) AGAINST CANINE-DISTEMPER

An inactivated canine distemper vaccine with adjuvant and a modified-l ive virus (MLV) vaccine were evaluated using black-footed ferret (Must ela nigripes) x Siberian polecat (Mustela eversmanni) hybrids as surro gates for endangered black-footed ferrets. For comparative purposes, w e also vaccinated domestic ferrets (Mustela putorius furo) with the ML V vaccine. Response to vaccination was measured by clinical observatio n, hematology, dynamics of serum virus neutralizing antibodies, and ch allenge with virulent canine distemper virus. No clinical signs attrib utable to the vaccines were observed. Transient leukopenia occurred in hybrid ferrets that received MLV vaccine and there was marked lymphop enia for approximately 52 days post-vaccination. Lymphopenia was prese nt for approximately 21 days in domestic ferrets vaccinated with MLV v accine. Neutralizing antibodies against canine distemper virus were de tected 14 days postvaccination in hybrids receiving MLV vaccine and mo st titers were >1:1024 for the 791 days of the study. Antibody titers in hybrids vaccinated with the inactivated vaccine were significantly lower. All eight hybrid ferrets that received MLV vaccine survived cha llenge with virulent canine distemper virus without clinical disease. However, one of seven hybrids vaccinated with the inactivated vaccine developed canine distemper and was euthanized; two other hybrids becam e clinically ill but survived. The MLV vaccine may be useful in preven tion of canine distemper in black-footed ferrets, but until additional studies of efficacy and safety are completed, use of the inactivated vaccine is appropriate.