The Pigeon circovirus (PiCV) containing a circular single stranded DNA (approximately 2 kb) genome belongs to the genus Circovirus of the family Circoviridae. PiCV infections in pigeons ( Columba livia) have been reported worldwide. Currently, pigeon racing is becoming increasingly popular and considered to be a national sport in China, and even, the greatest competitions of racing pigeons are taking place in China. However, there are still no epidemiologic data regarding PiCV infections among racing pigeons in China. To trace the prevalence, genetic variation and evolution of PiCV in sick and healthy racing pigeons, 622 samples were collected from 11 provinces or municipalities in China from 2016 to 2019. Samples were tested by polymerase chain reaction. The results showed that the positive rate of PiCV was 19.3% (120/622) at the sample level and 59.0% (23/39) at the club level, thus suggesting that the virus was prevalent in Chinese racing pigeons. A sequence analysis revealed that the cap genes of the PiCV strains identified in our study displayed a high genetic diversity and shared nucleotide homologies of 71.9%–100% and amino acid homologies of 71.7%–100%. 28 and 36 unique amino acid substitutions were observed in the Cap and Rep proteins derived from our PiCV strains, respectively. Furthermore, The ATT and GTG were highly suspected to be the start codons of the Cap protein. A cap-gene-based phylogenetic analysis showed that the strains in this study could be further divided into seven clades (A, B, C, E, G, H, and I) and some of them were closely related to worldwide strains from different types of pigeons. A large number of recombination events (31 events) were also detected in the PiCV genomes from Chinese racing pigeons. These findings indicate that PiCV strains circulating in China exhibit a high genetic diversity.

The Pigeon circovirus (PiCV) which contains a circular single stranded DNA (approximately 2 kb) belongs to the genus Circovirus and the family Circoviridae. PiCV infections in pigeons (Columba livia) have been reported worldwide. Nowadays, pigeon racing is becoming increasingly popular and considered to be a national sport in China, and even, the greatest competitions of racing pigeons are stake place in China. However, there is no epidemiologic data on PiCV infections among racing pigeons in China. To trace the prevalence, genetic variation and evolution of PiCV in sick and healthy racing pigeons, 622 samples were collected from 11 provinces or municipalities of China from 2016 to 2019. Samples were tested by polymerase chain reaction. The results showed that the positive rate of PiCV was 19.3% (120/622) at the sample level; 59.0% (23/39) at the club level, suggesting that the virus was prevalent in Chinese racing pigeons. A sequence analysis revealed that the cap genes of the PiCV strains identified in our study display high genetic diversity and shared nucleotide homologies of 71.9%–100% and amino acid homologies of 71.7%–100%. 28 and 37 unique amino acid substitutions were observed among the cap proteins and rep proteins of our PiCV strains, respectively. Furthermore, two initiation codons (GTG and ATT) of cap gene were newly found. A cap-gene-based phylogenetic analysis showed that the strains in this study could be further divided into six groups (A, B, C, E, G, H and I) and some of our strains are closely related to worldwide strains from different types of pigeons. A large number of recombination events (31 events) were also detected in the PiCV genomes from Chinese racing pigeons. These findings suggest that PiCV strains circulating in China exhibits higher genetic diversity.