Genetic characterization and recombination analysis of atypical porcine pestivirus

Atypical porcine pestivirus (APPV) is recognised as the etiology of congenital tremor (CT) Type A-II and poses a challenge to pig production. Here, we described a CT case in piglets caused by APPV infection in central China in 2017. Interestingly, different from a previous report, more CT litters were observed in the second and third parity sows compared to the first and fourth parity. Evolutionary analysis and recombination evaluation were conducted for the isolate and 61 APPV genomes were available in GenBank. Phylogenetic analysis revealed a high level of genetic variation of APPV and the coexistence of three clades (Clades I-III) in China. The isolate was clustered into Clade I, which seemed to be prevalent worldwide and displayed higher genetic variability (Subgroups 1-4) compared with Clade II and Clade III, both of which were only reported in China. Notably, three putative recombinants were identified and characterized in APPV. The recombination events occurred in interclades (Clade II and III) or intra-clades (Clade I). To the best of our knowledge, this study presents the first evidence of homologous recombination within Pestivirus K. These results provide new clinical presentations of APPV infection and may be helpful in better understanding the large amount of genetic variations in this genus.