Avirulent mutants of rabies virus and their use as live vaccine

Oral vaccination of foxes against rabies began in Switzerland some 20 years ago and was later extended to several European countries. The vaccine strains, which were derivatives of the SAD strain of rabies, retain a non-negligible pathogenicity for rodents and nontarget species. Antigenic mutants of the SAD Bern vaccine strain, which are avirulent for adult mice, foxes and dogs, have been isolated and are presently under trial.