Detection And Genetic Evolution Analysis Of Pigeon Circovirus In A Large-scale Pigeon Farm

Pigeon circovirus(PiCV),a new member of the circoviridae family,is now considered young pigeon pathogenic cause of disease syndrome(YPDS).Like most circoviruses,pigeon circoviruses can accelerate its replication in proliferating cells and immune system cells,resulting in low lymphocyte ratio and low immunity,damaging to pigeon immune system,which can be followed by secondary infection with other pathogens.In order to understand the infection situation of PiCV in a large-scale pigeon farm in Hotan,Xinjiang,716 feces samples were collected from the farm.According to the published sequences of PiCV in GenBank,the detection primers were designed to amplify the sequences of PiCV in the farm by PCR.That was consistent with the expected size of 317 bp were obtained,which were confirmed as PiCV specific sequence by sequencing.The positive rate of picv was 69.97%(501/716).The results showed that there was a serious infection of PiCV in the pigeon farm.In order to analyze the possible source of PiCV of the farm,the two main ORFs of PiCV detected,namely OFR V1(Rep)and ORF C1(Cap)genes,and the entire virus genes of the virus were analyzed in this study.Three pairs of primers were designed to amplify the PiCV Cap,Rep gene and the entire virus gene sequence in the liver tissue sample of diseased pigeon,to obtain DNA fragments with the expected sizes of 898 bp,992 bp and 2 031 bp,respectively.The genes were cloned and sequenced,after sequencing of the genome sequences by BLASTn,identified as PiCV Cap,Rep and complete gene.Sequence alignment analysis showed that the positive samples tested had the same source of pathogen,so it was named PiCV-XJ2018.And MEGA5.0 was applied to carry out genetic and evolutionary analysis of PiCV-XJ2018 and over 30 PiCV sequences at home and abroad to explore the possible source of PiCV-XJ2018.The results showed that the nucleotide homology of Cap gene between picv-xj2018 and GF82/guangdong/2014(KX108805)strain was 94.98%,and that the nucleotide homology of Rep gene between picv-xj2018 and GF71/guangdong/2014(KX108799)strain was 97.17%.The phylogenetic analysis showed that the PiCV-XJ2018 strain was closely related to the Guangdong and Shanghai strains detected in 2014.Then,the complete gene sequence of the strain PiCV-xj1/2018 was compared and analyzed with that of 36 PiCV strains at home and abroad.The results showed that the nucleotide homology and amino acid homology of PiCV-xj1/2018 strain and GF17/Guangdong/2014(KX108806)were 94.7%and 94.6%respectively.The nucleotide homology of 37 whole genes ranged from 85.2%to 94.7%.The results of genes genetic evolution analysis showed that the strain of PiCV-xj1/2018 was closely related to the strains from guangdong,Shanghai and Jiangsu in 2014,and the closest to the guangdong strain in 2014.In summary,PiCV in the large-scale pigeon farm was investigated,and the results showed that a certain proportion of PiCV(positive rate of 69.97%)existed in the investigated pigeon group.This was the first time that circovirus was detected and confirmed in the pigeon group in xinjiang.Sequence analysis showed that the strain of PiCV in xinjiang had the highest homology and the closest relationship with the guangdong strain.The study will provide data reference for the prevention and control of pigeon circovirus in Xinjiang.Analysis of virus gene sequence lays a foundation for the establishment of diagnosis method and the study of pathogenic mechanism of PiCV.