Protective antibody response in Korean raccoon dogs (Nyctereutes procynoide koreensis) administered a new rabies bait vaccine containing the ERAGS-GFP strain.

Abstract

Purpose: Rabies is a deadly zoonotic disease affecting many mammals, including humans. Oral rabies bait vaccines induce an immune response without direct inoculation, and are crucial for controlling rabies in wildlife. This study evaluated the safety and immunogenicity of a new rabies bait vaccine containing a recombinant rabies virus expressing green fluorescent protein (ERAGS-GFP) in wild raccoon dogs.

Materials and methods: To confirm the safety of the ERAGS-GFP vaccine, reversion to virulence was evaluated in 1-day-old suckling mice. The uptake, minimum effective dose, and immunogenicity of the bait vaccine were assessed in raccoon dogs, as was the persistence of post-vaccine immunity. Serum rabies virus neutralizing antibody (VNA) titers were measured using fluorescent antibody virus neutralization.

Results: No adverse effects were noted in mice, guinea pigs, dogs, or raccoon dogs administered the ERAGS-GFP vaccine orally during the test period. The glycoprotein gene of the ERAGS-GFP strain remained unchanged after five reverse passages in 1-day-old mice. Uptake of the bait vaccine was 75.8% in raccoon dogs. The minimum effective dose was at least 10^5.0 TCID₅₀/mL. Forty-three raccoon dogs administered the ERAGS-GFP bait vaccine developed an average VNA titer of 4.23 IU/mL 28 days post-administration. Protective antibody levels were maintained for 4 months.

Conclusion: The ERAGS-GFP bait vaccine showed high uptake and strong immunogenicity in raccoon dogs, and protective antibody levels were maintained for at least 4 months. These results indicate the vaccine's potential for effective rabies control in wildlife, which can reduce the risk of transmission to humans and domestic animals.