Investigation of the epidemiology, pathogenicity and immunogenicity of Bordetella bronchiseptica isolated from cats and dogs in China from 2021 to 2023

Abstract

AbstractBordetella bronchiseptica (Bb) is recognized as a leading cause of respiratory diseases in dogs and cats. However, epidemiological data on Bb in dogs and cats in China are still limited, and there is no commercially available vaccine. Live vaccines containing Bb that are widely used abroad are generally effective but can establish latency and potentially reactivate to cause illness in some immunodeficient vaccinated recipients, raising safety concerns. In this study, 34 canine-derived and two feline-derived Bb strains were isolated from 1809 canine and 113 feline nasopharyngeal swab samples collected from eight provinces in China from 2021 to 2023. The PCR results showed that the percentage of positive Bb was 22.94% (441/1922), and more than 90% of the Bb isolates had four virulence factor-encoding genes (VFGs), namely, fhaB, prn, betA and dnt. All the isolated strains displayed a multidrug-resistant phenotype. The virulence of 10 Bb strains isolated from dogs with respiratory symptoms was tested in mice, and we found that eight isolates were highly virulent. Furthermore, the eight Bb isolates with high virulence were inactivated and intramuscularly injected into mice, and three Bb strains (WH1218, WH1203 and WH1224) with the best protective efficacy were selected. Dogs immunized with these three strains exhibited strong protection against challenge with the Bb field strain WH1218. Ultimately, the WH1218 strain with the greatest protection in dogs was selected as the vaccine candidate. Dogs and cats that received a vaccine containing 109 CFU of the inactivated WH1218 strain showed complete protection against challenge with the Bb field strain WH1218. This study revealed that Bb is an important pathogen that causes respiratory diseases in domestic dogs and cats in China, and all the isolates exhibited multidrug resistance. The present work contributes to the current understanding of the prevalence, antimicrobial resistance, and virulence genes of Bb in domestic dogs and cats. Additionally, our results suggest that the WH1218 strain is a promising candidate safe and efficacious inactivated Bb vaccine.