Recombinant rabies vaccines: efficacy assessment in free-ranging animals

With the advancement of recombinant DNA techniques, a number of potent biologicals are available for the oral vaccination of free-ranging animals. Once oral immunogenicity and vaccine safety have been demonstrated, efficacy then becomes of paramount importance. Classical assessment of efficacy is conducted under carefully controlled laboratory conditions, whereas efficacy of oral wildlife rabies vaccination programs, to date, have been assessed by the lack (or occurrence) of field cases of rabies in a vaccinated area. This communication describes an intermediate vaccine efficacy strategy in which self-vaccinated, free-ranging animals from a study site were captured seven months after vaccine-laden bait distribution for laboratory rabies challenge. This technique is specifically reviewed in the context of available recombinant products for the consideration of extension towards dog rabies control.