Abstract
To trace the evolution of canine coronavirus (CCoV), 201 stool samples from diarrheic dogs in northeast China were subjected to reverse transcription-polymerase chain reactions (RT-PCRs) targeting the partial M and S genes of CCoV, followed by an epidemiological analysis. M gene RT-PCRs showed that 28.36% (57/201) of the samples were positive for CCoV; of the 57 positive samples, CCoV-I and CCoV-II accounted for 15.79% (9/57) and 84.21% (48/57), respectively. A sequence comparison of the partial M gene revealed nucleotide homologies of 88.4%–100% among the 57 CCoV strains, and 88.7%–96.2% identity between the 57 CCoV strains and the Chinese reference strain HF3. The CCoV-I and CCoV-II strains exhibited genetic diversity when compared with reference strains from China and other countries. The 57 CCoV strains exhibited high co-infection rates with canine kobuvirus (CaKV) (33.33%) and canine parvovirus-2 (CPV-2) (31.58%). The CCoV prevalence in diarrheic dogs differed significantly with immunization status, regions, seasons, and ages. Moreover, 28 S genes were amplified from the 57 CCoV-positive samples, including 26 CCoV-IIa strains, one CCoV-IIb strain, and one CCoV-I strain. A sequence comparison of the partial S gene revealed 86.3%–100% nucleotide identity among the 26 CCoV-IIa strains, and 89.6%–92.2% identity between the 26 CCoV-IIa strains and the Chinese reference strain V1. The 26 CCoV-IIa strains showed genetic diversity when compared with reference strains from China and other countries. Our data provide evidence that CCoV-I, CCoV-IIa, and CCoV-IIb strains co-circulate in the diarrhoetic dogs in northeast China, high co-infection rates with CaKV and CPV-2 were observed, and the CCoV-II strains exhibited high prevalence and genetic diversity.
Highlights
Canine coronavirus (CCoV) was first recognized as an enteric pathogen of dogs in 1971 [1]
Of the 201 samples, 57 samples (28.36%) were positive for CCoV following reverse transcription-polymerase chain reaction (RT-PCR) amplification of the partial M gene, and the CCoV-positive rates of the Harbin, Daqing, and Mudanjiang districts were 26.95%, 50%, and 22.5%, respectively (Table 1)
Age 0< Age 1M 1M< Age 2M 2M< Age 3M 3M< Age 4M Coinfection of CCoV with other enteric viruses Single infection canine parvovirus-2 (CPV-2) canine kobuvirus (CaKV) canine bocavirus (CBoV) Mixed infection CPV-2+CaKV CPV-2+CBoV+CaKV Total co-infection CaKV, CPV-2, CBoV, CPV-2+CaKV or CPV-2+CBoV+CaKV Identity of partial M gene of CCoV identified in our study Nuleotides I II I+II Amino acids I II I+II Compared with M gene of the HF3 strain from China (AY864661) Nuleotides I+II Amino acids I+II Identity of partial S gene of CCoV identified in our study Nuleotides IIa Amino acids IIa
Summary
Canine coronavirus (CCoV) was first recognized as an enteric pathogen of dogs in 1971 [1]. CCoV is a common infection in young dogs, those housed in large groups [2,3,4,5]. Accumulating reports attributed that the increase in the severity of CCoV infections in dogs and the emergence of CCoV variants to potential recombination events within the S gene, which occur when a host is co-infected with different CCoV types [8,9,10]. CCoV has received much attention as an emerging cause of infectious disease in dogs [4, 11,12,13,14,15,16]
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