The Prevalence, Coinfection, and Evolutionary and Molecular Characteristics of Prevalent Goose Circovirus in Guangdong, China

To understand the prevalence, coinfection with other viruses, underlying genetic evolution, recombination, and molecular biological characteristics of goose circovirus (GoCV) in Guangdong, China, from December 2019 to August 2020, 310 tissue samples of geese showing stunted growth and feather disorder syndrome were collected from this region and analyzed. GoCV, Tembusu virus, waterfowl paramyxovirus, avian influenza virus, fowl adenovirus type 4, and duck plague virus were detected with PCR or real-time PCR. Thirty-one complete GoCV viral genomes were obtained from 164 PCR-verified GoCV nucleotide-positive samples and subjected to phylogenetic analysis, gene recombination analysis, and genome secondary structure prediction. The results showed that more than half of the samples were GoCV positive, and 31.1% of the GoCV-positive samples were from coinfections with at least one of the other viruses. The phylogenetic analysis showed that the GoCVs could be divided into three genome types. The genes of most main epidemic strains now circulating in Guangdong belonged to the Ia subtype, and some strains gradually formed a new Ib subtype. The secondary structure of the viral genome was similar to that of other known circoviruses. Furthermore, B cell linear epitope prediction and protein structure homology modeling of the viral capsid protein were performed based on the viral amino acid sequences. The results showed that the spatial structure of the capsid protein of the 31 sequenced strains was similar to that of duck circovirus and consisted of two β-sandwich conformations. A total of five B cell linear epitopes were predicted, and four of them were mapped on the predicted model of the capsid protein of GoCVs. This report provides a reference for the epidemiology of GoCV in Guangdong, understanding the elemental composition of the virus genes and proteins, selecting representative vaccine strains, constructing targeted immune preparations for GoCV, and strengthening prevention and control of the disease.