Stability of recombinant vaccinia-rabies vaccine in veterinary use.

Wildlife vaccination depends on vaccines which can be orally administered by a baiting system. Therefore only two possibilities exist: either the use of attenuated strains of viruses, or recombinant vector viruses. As far as rabies is concerned, the choice of the recombinant vaccinia-rabies virus was made because it was safer and more stable. An in vitro stability study of the recombinant product compared to wild rabies virus at different temperatures (4 degrees C, 20 degrees C, 37 degrees C, 45 degrees C) showed that the recombinant virus was more stable. The stability of the recombinant virus was also tested under field conditions; besides natural freezing and thawing cycles, the virus titre remained unchanged in the bait for a month. Taking into account the fact that all baits are eaten by wild animals within this period, one can assume that the vaccine is efficacious for all baiting animals in field conditions. The stability of the recombinant vaccinia-rabies vaccine is of considerable interest in such uncontrolled conditions.