Development of a Recombinant Vaccinia-Rabies Vaccine for Oral Vaccination of Foxes against Rabies

To improve both safety and stability of the vaccines used in the field to vaccinate foxes against rabies by the oral route, a recombinant vaccinia virus, expressing the immunizing G protein of rabies virus (VVTGg RAB-26D3 187 X P strain) has been developed. The c-DNA corresponding to the glycoprotein of the ERA strain of rabies virus has been inserted into the thymidine kinase (TK) gene of the vaccinia virus (Copenhagen strain). The efficacy of this recombinant strain was tested by the oral route, primarily in foxes. The duration of immunity conferred by the VVTGg RAB, a minimum of 12 months in cubs and 18 months in adult animals, corresponds to the length of protection required for fox vaccination in the field. VVTGg RAB innocuity was tested in foxes and in domestic animals as well as in numerous wild animal species that could compete with the red fox in consuming vaccine baits in Europe. During a minimum of 28 days post vaccination, neither clinical signs nor lesions were observed in any of the vaccinated animals. Moreover no transmission of immunizing amounts of the recombinant occurred in the red fox or the other species tested. To study the stability of the vaccine strain, baits containing the vaccine were placed in the field. Despite considerable variations of environmental temperatures, the VVTGg RAB titre remained stable after one month in the field. Since all the baits are taken within one month, it can be assumed that most of the animals taking the baits are effectively vaccinated.