Molecular detection and phylogenetic analysis ofPorcine circovirus4 in Henan and Shanxi Provinces of China

Porcine circovirus4 (PCV4), a new circovirus with a distinct relationship to other circoviruses, was identified in 2019 in several pigs with severe clinical disease in Hunan Province, China. To investigate the epidemic profile and genetic diversity of the virus, 63 clinical samples were collected from 24 different pig farms in 14 cities in Henan and Shanxi Provinces, China, between February 2018 and December 2019, and the partialCapgene of PCV4 was amplified by PCR. Among the 63 samples, 16 (25.40%) were positive for PCV4, and 50% (12/24) of the pig farms were positive for PCV4. PCV4 was detected in samples from pigs with different clinical presentations. One PCV4 strain (Henan-LY1-2019) was sequenced in this study, and shared 98.4% genomic nucleotide identity with PCV4 strain HNU-AHG1-2019 (accession no. MK986820) detected on a pig farm in Hunan Province in 2019. A phylogenetic analysis based on the genomes of Henan-LY1-2019 and 31 reference strains showed that the Henan-LY1-2019 strain together with PCV4 strain HNU-AHG1-2019 was grouped in a relatively independent sub-branch, and separated from other viruses in the genusCircovirus. The results of this study extend our understanding of the molecular epidemiology of PCV4.