Investigating the Presence and Genetic Variability of Porcine Circovirus Types 2 and 3 in Live Markets in Border Cities of Northeast China

Bordering cities and farms serve as potential hotspots for the transboundary spread of animal infectious agents. This study aimed to investigate the presence and genetic variability of porcine circovirus types 2 (PCV2) and 3 (PCV3) in live markets across six border cities (Dandong, Ji'an, Hunchun, Mishan, Fuyuan, and Heihe) in northeast China. Samples from pork (<i>n</i> = 44), cutting boards (<i>n</i> = 46), and meat stall floors (<i>n</i> = 42) were collected in 46 meat stalls. Quantitative PCR analysis detected PCV2 in 75.0% (95% CI: 59.7%-86.8%) of pork samples, 73.9% (95% CI: 58.9%-85.7%) of cutting board swabs, and 64.3% (95% CI: 48.0%-78.4%) of meat stall floor swabs. For PCV3, the detection rates in pork, cutting board swabs, and meat stall floor swabs were 31.8% (95% CI: 18.6%-47.6%), 67.4% (95% CI: 52.0%-80.5%), and 54.7% (95% CI: 38.7%-70.2%), respectively. Subsequent sequencing of positive samples identified five open reading frame (ORF)2 sequences of PCV2 from markets in Dandong, Fuyuan, and Hunchun, with one sequence from Dandong shared 99.4% homology with a Russia sequence. Similarly, five ORF2 sequences of PCV3 were obtained from samples in Hunchun, Heihe, and Ji'an, including a sequence from Hunchun showing 99.6% homology to a sequence from a pig farm in Changchun in Jilin Province. These findings suggest that border market pork trade may contribute to the introduction and dissemination of PCV2 and PCV3. The observed genetic similarities highlight potential transboundary transmission routes, emphasizing the need for active surveillance and control measures to mitigate the risks associated with the transboundary transmission of emerging swine pathogens.