The quest for a safe and effective canine distemper virus vaccine for black-footed ferrets

Canine distemper virus (CDV) causes a systemic disease that is highly virulent to mustelids and other carnivore (Order Carnivora) species and is found worldwide. Endemic canine distemper in wild and domestic carnivores in the United States has made reintroduction of endangered black-footed ferrets (Mustela nigripes) difficult in the absence of safe and effective CDV vaccines and vaccination practices. Toward this end, researchers have explored appropriate animal models and vaccine preparations in highly susceptible species. Published studies involving domestic ferrets (M. putorius furo) using Galaxy-D® and evaluating a recombinant canarypox-vectored vaccine for oral administration are reviewed. In addition, we present new findings in domestic and black-footed ferrets and Siberian polecats (M. eversmannii) that have extended our understanding of CDV in the black-footed ferret and other at-risk carnivore species. Original research presented here includes trials that determined an effective challenge dose (by route) of virulent CDV in domestic ferrets and Siberian polecats; the low likelihood of collateral vaccination with Galaxy-D; the adverse effect of modified-live virus boostering in black-footed ferrets receiving killed vaccine previously and the response of Siberian polecats receiving canarypoxvectored recombinant CDV vaccine (reCDV); the absence of an effect of reCDV vaccination on conception, pregnancy, and neonatal growth in Siberian polecats; and the apparent inefficacy of active reCDV vaccination during the period of passive immunity in young Siberian polecats. In the final section, we discuss emerging concerns and avenues for disease intervention that may present new opportunities to solve problems in vaccine safety, vaccine availability, field vaccine delivery, and other therapeutic modalities.