Evaluation of the immunobiological properties of an oral briquette rabies vaccine in foxes

Rabies remains one of the most dangerous zoonotic infections maintained in natural reservoirs among wild carnivorous animals. Despite the high efficacy of inactivated vaccines in domestic animals, rabies control in wildlife requires the use of oral vaccines capable of providing mass immunization of naturally susceptible species. The aim of the present study was to evaluate the immunogenicity, safety, and protective efficacy of an oral briquetted rabies vaccine tested in naturally susceptible carnivorous animals. Clinically healthy rabies-seronegative foxes were used in the experiment. To assess immunogenicity, animals received a single oral administration of a briquetted vaccine containing a fixed rabies virus strain. Vaccine safety was evaluated using an increased dose (10 baits per animal). The dynamics of the humoral immune response were assessed using the mouse neutralization test and ELISA. Protective efficacy was determined by challenge infection with the CVS test strain. The results demonstrated that the vaccine was readily consumed by the animals and did not cause clinical adverse reactions or deviations from physiological norms. Vaccinated animals developed a pronounced humoral immune response, with mean virus-neutralizing antibody titers exceeding the protective level of 0.5 IU/ml and reaching peak values on day 21 post-immunization. Following challenge infection, all vaccinated animals survived and showed no clinical signs of rabies, whereas control animals developed the paralytic form of the disease with a fatal outcome. Thus, the obtained data demonstrate the high immunogenicity, safety, and protective efficacy of the oral briquetted rabies vaccine and confirm its potential for use in oral immunization programs targeting carnivorous wildlife species and the control of natural rabies foci.