Investigation of circulating infectious agents in experimental Beagle dogs of a production colony and three research facilities in China from June 2021 to May 2022

To understand the epizootiologic characteristics of pathogens and opportunistic infections in one Beagle dog production colony and three research facilities, viruses and mycoplasma were detected in 1777 samples collected from Beagle dogs in China by polymerase chain reaction/reverse transcription polymerase chain reaction, and bacteria were isolated and identified by 16S rRNA sequence analysis. In addition, genotyping of the major circulating viruses was carried out by amplification of gene fragments and homology analysis. Canine coronavirus (CCoV), Escherichia coli, canine parvovirus (CPV), Bordetella bronchiseptica, Clostridium perfringens, Mycoplasma cynos, Klebsiella pneumoniae, Streptococcus canis, canine astrovirus (CaAstV), canine kobuvirus (CaKV), Pseudomonas aeruginosa, Proteus mirabilis, Macrococcus canis, Pasteurella canis, canine bocavirus (CBoV) and canine adenovirus (CAdV) were detected in the samples. Single, double, triple and quadruple infections accounted for 6.6%, 1.4%, 1.2% and 0.96% of samples, respectively. CCoV strains in 81 samples included three genotypes, CCoV-I, CCoV-IIa and CCoV-IIb, by analysis of S gene. The rate of single infection of CCoV-I, CCoV-IIa or CCoV-IIb was 19%, 38% or 7.4% respectively. The double and triple infection rates of CCoV were 32.8% and 2.5% respectively. All CPV strains in 36 samples belonged to CPV-2c. There were three amino acid differences in the Fiber protein of CAdV-positive sample QD2022, compared with the reference strain Toronto A26/61 and the vaccine strain YCA-18. These results suggest that CCoV and CPV are primary infectious agents, and that these two viruses were often identified in mixed infections, or coinfections alongside mycoplasma or other bacteria. These results will provide the basis for improvements in prevention and control of naturally occurring infectious diseases in Beagle dog production colonies and research facilities.