Molecular Epidemiological Investigation And Gene Characteristic Anaiysis Of Bovine PCV3 In Xinjiang

Objective: Porcine circovirus type 3(PCV3)had been identified in domestic pigs for the first time by US researchers since 2016.PCV3 infection had also been reported in many provinces of China.At present,PCV3 has been detected in cattle,dogs,mice and ticks and other animals except natural host.However,the infection of PCV3 to cattle in Xinjiang has not been known.In order to find out the infection situation and gene characteristics of PCV3 in cattle in Xinjiang,this study investigated the infection of PCV3 in large-scale cattle farms in Xinjiang.Methods: In this study,670 samples from 13 representative regions in Xinjiang were detected for PCV3 gene by nested PCR,and the nucleotide sequence was analyzed.At the same time,combined with rose bengal test(RBT)and ordinary PCR detection,the positive samples of PCV3 were detected brucellosis antibody and gene of diseases related to bovine reproductive disorders,and analyzed the relationship between PCV3 and other pathogens.The representative PCV3 positive samples were selected for whole gene amplification,sequencing and splicing,and the whole genomic sequence was analyzed.Using recombinat PCV3 capsid protein provided by the laboratory as antigen,an indirect ELISA-PCV3 antibody detection method was established to detect the antibody of bovine serum samples infected with PCV3,and the results were statistically counted.Results:(1)A total of 131 positive samples of PCV3 were detected in 670 samples from 13 regions,with an average positive rate of 19.55%(131/670).The presence of PCV3 was detected in large-scale cattle farms in various regions,with a positive rate of 5.00%-35.00%;the positive rate of PCV3 in different tissues of 30 cattle was found to be 10.00%-26.67%,the positive rate of lymphoid infection was the highest of 26.67%(8/30);The average positive rate of PCV3 in different growing stages 12.50%(15/120),one year old cattle had the highest positive infection rate of 33.33%(4/12).By investigating the coinfection between PCV3 and other pathogens,it was found that PCV3 was isolated in cattle,the positive rate was 61.83%(81/131);the positive rate of double infection between PCV3 and BVDV? BHV-1?BPIV-3 was 10.69%-33.59%;the positive rate of multiple infection between PCV3 and BVDV?BHV-1?BPIV-3 was 5.34%-9.16%.(2)The whole genomic sequences of the 10 PCV3 strains obtained in this study had a high homology of 98.4%-99.8% and 96.3%-99.7% with other PCV3 reference strains at home and abroad.It was found that five PCV3 whole genomic sequences were in the same branch as PCV3-US-MN2016,belonging to 3a subgroup;two of them were in the same branch as PCV3-KU-1607,belonging to 3b subgroup;the remaining three whole genomic sequences were in the same branch as PCV3-CN-FuJian-318-2017,belonging to 3c subgroup.The prevalence of PCV3 in Xinjiang cattle population showed genotype diversity.The physical and chemical properties of 10 capsid proteins were similar,all of them had no signal peptide and belonged to hydrophilic protein,and the predicted phosphorylation sites were the same.(3)The preliminary indirect ELISA-PCV3 antibody test results showed that the average positive rate was 63.75%(408/640).The average positive rate of PCV3 antibody in different growth stages was 57.50%(69/120),indicating the possibility of PCV3 infection in cattle.Conclusion: The results showed that PCV3 was detected in Xinjiang cattle for the first time.It was found that PCV3 had been existed in cattle in Xinjiang,and it could be distributed in different tissues of infected bovine.At the same time,it was possible to infect PCV3 in different growth stages of cattle.PCV3 had single,double and multiple infection with the pathogens related to bovine reproductive disorders in cattle,It indicated that PCV3 might be a potential threat to bovine health;The whole genomic sequences of PCV3 obtained in this study had high homology and certain genotype diversity;The preliminary established indirect ELISA-PCV3 antibody detection method had certain reliability,which provided convenience for serological detection.