Prevalence and genetic characterization of Porcine Circoviruses in Thai swine farms during 2019-2020

Abstract

To date, porcine circoviruses (PCVs), particularly PCV2 and PCV3, have been identified globally, while PCV4 is mainly found in Asia. This study aimed to investigate the prevalence and genetic characterization of PCVs in Thai swine farms during 2019-2020. Results showed PCV2 is the predominant species, followed by PCV3 and PCV4. For genetic analysis, the dominant novel PCV2d cluster with amino acid mutation (133HDAM136) in ORF2 was found in Thai swine farms that had not been detected in Thailand before. Moreover, inter-genotypic recombinant PCV2b/d was first identified in Thailand. The genetic analysis of PCV3 showed that PCV3 was grouped into PCV3a with high genetic stability among Thai PCV3 strains. Notably, this study presents the first report of PCV4 in Thailand. Genetic analysis revealed that Thai PCV4 strains belong to the PCV4b classification and are closely related to PCV4 strains from China. Furthermore, our research identified the viral tropism of PCV4 in bronchial epithelial cells using in situ hybridization, shedding light on its pathogenesis. Furthermore, we developed a triplex real-time PCR assay (tqPCR) for simultaneous detection. The tqPCR assay offers several advantages, including reduced testing time, high sensitivity and specificity, and the ability to conduct quantitative analyses, making it a valuable tool for clinical diagnostics and epidemiological studies of PCV2, PCV3, and PCV4 in the future. In conclusion, our study confirms the presence of PCV2, PCV3, and PCV4 in Thai swine farms. These findings emphasize the importance of ongoing surveillance and research efforts to gain a deeper understanding of these viruses and to develop effective prevention and control strategies for the swine industry.