Rapid clearance of SAG-2 rabies virus from dogs after oral vaccination

This study investigated the safety, efficacy, and clearance of SAG-2. an at tentuated rabies virus, after oral vaccination in dogs. Nineteen dogs consu med baits containing lyophilized vaccine, but residual SAG-2 virus was reco vered in only one of 57 oral swabs, collected one hour post-vaccination. Se ven vaccinates were euthanized between 24 and 96 h after consuming a bait. Rabies virus RNA was detected in tonsils from all seven dogs by nested RT-P CR, with primers to the viral glycoprotein. Genomic, sense-transcripts. and m-RNAs were detected in five of seven tonsil samples using primers to the rabies virus nucleoprotein gene, as well as in four of seven samples from t he buccal mucosa and one of seven from the tongue. Rabies virus antigen was detected in all tonsils by an immunohistochemistry test, confirming the RT -PCR results. In addition, virus was isolated from one tonsil sample collec ted at 96 h. providing supportive evidence of viral replication. Ten of 12 (83%) of the vaccinated dogs demonstrated an anamnestic response, with vira l neutralizing antibody titers (greater than or equal to 0.5 IU/ml), after rabies virus challenge. These ten dogs survived., whereas all control dogs succumbed to rabies. Attenuated rabies viruses, such as SAG-2. replicate in local tissues of the oral cavity and can be cleared relatively quickly, wi thout viral excretion, leading to protective immunity against the disease. Published by Elsevier Science Ltd.