Oral vaccination of dogs (Canis familiaris) with baits containing the recombinant rabies-canine adenovirus type-2 vaccine confers long-lasting immunity against rabies.

Rabies is a reemerging and fatal infectious disease in Asia mainly caused by exposure to rabid dogs. Prevention of dog rabies would be the most effective way to stop rabies transmission to humans. However, vaccinating stray dogs in urban and rural areas using conventional vaccines is always difficult and is not cost-effective for use in most areas including China. Further to previous studies from our laboratory, we developed a bait containing the recombinant rabies vaccine and performed a non-parenteral trial in dogs. This vaccine was intranasally administrated once to 46 dogs in solution form with 1 x 10(8.5) PFU and orally to 90 dogs in specially designed baits with 3 x 10(8.5) PFU of the recombinant canine adenovirus. Results showed that about 87.5% (119/136) of the immunized dogs developed virus neutralizing antibodies (VNA). The immune response against rabies in dogs was detectable at 2-3 weeks after administration, reaching a peak by 5-6 weeks. Among the seroconverted animals, 90.8% (108/119) elicited a VNA response for over 24 months. The antibody titer during the 2 years was above 0.5IU /ml while showing a gradual but slow decline from the 6th week after vaccination. In a challenge experiment of 10 dogs with 60,000 mouse LD(50) of CVS-24 2 years after the vaccination, all the dogs survived. This demonstrated that the recombinant vaccine could be orally administrated and the bait was effective for the oral vaccination of dogs.