The place of marker vaccines in control and eradication of animal diseases : aspects of comparative interest

Smallpox is the first viral infection to have been eradicated world-wide. This remarkable success is due to several factors including the availability of an efficacious vaccine and the absence of a wildlife reservoir. The only animal virus disease sharing these characteristics is rinderpest, for which there are several efficacious vaccines. Other animal viral infections do not share the same characteristics, either due to the lack of an efficacious vaccine (African swine fever), or to the existence of wildlife reservoirs such as the wild boar for classical swine fever, the African buffalo for foot-and-mouth disease, bats for lyssavirus infections, etc. These diseases are more prone to regional elimination than a complete worldwide eradication. Two methods are used to eliminate an animal viral infection, either vaccination or the strict application of hygienic measures including stamping out and incineration, or the combination of both methods. Public opinion is more and more concerned about stamping out, even when necessary such as when dealing with emerging zoonoses. On the other hand, generalised vaccination (i.e. against foot-and-mouth disease, classical swine fever, etc.) may be discontinued despite its efficacy, for macro-economical reasons. The solution may come from the use of marker vaccines associated with companion diagnostic tests to make a distinction between infected and immunised animals by serological examination. Current control and eradication programmes against these and other diseases, the role of marker vaccines, and the limitations of such programmes are being discussed.