Assessment of the immunogenicity of rabies vaccine preserved by vaporization and delivered to the duodenal mucosa of gray foxes (Urocyon cinereoargenteus).

Abstract

OBJECTIVE To assess the immunogenicity of thermostable live-attenuated rabies virus (RABV) preserved by vaporization (PBV) and delivered to the duodenal mucosa of a wildlife species targeted for an oral vaccination program. ANIMALS 8 gray foxes (Urocyon cinereoargenteus). PROCEDURES Endoscopy was used to place RABV PBV (n = 3 foxes), alginate-encapsulated RABV PBV (3 foxes), or nonpreserved RABV (2 foxes) vaccine into the duodenum of foxes. Blood samples were collected weekly to monitor the immune response. Saliva samples were collected weekly and tested for virus shedding by use of a conventional reverse-transcriptase PCR assay. Foxes were euthanized 28 days after vaccine administration, and relevant tissues were collected and tested for presence of RABV. RESULTS 2 of 3 foxes that received RABV PBV and 1 of 2 foxes that received nonpreserved RABV seroconverted by day 28. None of the 3 foxes receiving alginate-encapsulated RABV PBV seroconverted. No RABV RNA was detected in saliva at any of the time points, and RABV antigen or RNA was not detected in any of the tissues obtained on day 28. None of the foxes displayed any clinical signs of rabies. CONCLUSIONS AND CLINICAL RELEVANCE Results for this study indicated that a live-attenuated RABV vaccine delivered to the duodenal mucosa can induce an immune response in gray foxes. A safe, potent, thermostable RABV vaccine that could be delivered orally to wildlife or domestic animals would enhance current rabies control and prevention efforts.