Effects of modified live-virus canine distemper vaccines in Gray Foxes

Thirty Gray Foxes (Urocyon cineroargenteus) were inoculated with a modified live-virus canine distemper vaccine of avian and canine cell origin to determine the efficacy of such vaccines in Gray Foxes. Five additional Gray Foxes were used as controls and received a placebo containing 5% dextrose solution in place of the vaccine. Foxes were considered normal, adult animals prior to inoculation; titers of serum antibody to canine distemper virus were less than or equal to 1:64 for each fox. Serum antibody titers were considered significant at greater than or equal to 1:100. Within 5 days post-vaccination, Gray Foxes within the vaccinated groups began exhibiting symptoms vaccine-induced canine distemper virus infection. All foxes that received modified live-virus distemper vaccines died within 17 days post-vaccination. Control animals remained healthy throughout the S-week postvaccination period. It is not advisable to vaccinate Gray Foxes with modified live-virus distemper vaccines, regardless of cell origin.