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Porcine circovirus type 3 has been circulating throughout the world and since their first report, various clinical signs and disease developments have been documented. The virus is similar to the closely related PCV2 and is associated with several clinical signs called porcine circovirus-associated diseases (PCVAD). PCV2 or PCV3 is occasionally reported with clinical signs such as PDNS, respiratory signs and reproductive failure. Retrospective research conducted in Thailand revealed that both PCV2 and PCV3 have been circulation for decades. However, awareness about PCV3 infection has just arisen in recent years because of the similarities observed in disease circulation and clinical signs that have led to concerns. This study was conducted to find the relationship between the quantity of PCV2 and PCV3 in Thai pigs displaying the clinical signs related to PCVAD. A total of 479 serum samples with different production phases and clinical signs were sent to Kamphaeng Saen Veterinary Diagnostic Center (KVDC) for qPCR to detect the presence of PCV2 or PCV3. There was no relationship between the PCV3 and PCVAD-related clinical signs. Also, the relationship between PCV2 and PCV3 with no clinical signs suggested that both viruses might come from the same reservoir or have been circulating in Thailand for a long time, leading to common incidents in finding. The viral load of PCV2 was significantly different among the pig groups with and without clinical signs. The capsid sequence analysis of PCV3 revealed that 22 capsid sequences obtained from this study were found as clusters within PCV3a with a minor variation. Additional control measures are further needed to reduce the findings of the viruses. A future study with a control experiment may be needed to clarify the pathogenesis of PCV3., (© 2021 Wiley-VCH GmbH.)

Porcine circovirus type 3 (PCV3) has recently been detected in pigs worldwide, with similar clinical manifestations to porcine circovirus-associated disease (PCVAD) from porcine circovirus type 2 (PCV2) infection. Here, we report the identification and molecular epidemiology of PCV3 in swine in Thailand from clinical samples retrieved from 2006 to 2017. The epidemiological data revealed co-infection with PCV2, PRRSV, and PCV2/PRRSV was common in our samples. Circulating PCV3 from this study shared a high similarity of nucleotide and deduced amino acid sequences of the partial capsid gene (96.7%-100% and 96.7%-100% respectively), indicated the genetic stability of PCV3 in Thailand. Phylogenetic analysis based on the capsid gene revealed scatter clustering with current PCV3 having no relation to the geographical origin of the virus strains. In this retrospective study, results have demonstrated that PCV3 has spread extensively within Thai swine from as early as 2006 and may also be involved in PRDC and PCVAD., (© 2018 Blackwell Verlag GmbH.)

Porcine circovirus type 2 (PCV2), the essential cause of porcine circovirus associated disease (PCVAD), has evolved rapidly and it has been reported worldwide. However, genetic information of PCV2 in Thailand has not been available since 2011. Herein, we studied occurrence and genetic diversity of PCV2 in Thailand and their relationships to the global PCV2 based on ORF2 sequences. The results showed that 306 samples (44.09%) from 56 farms (80%) were PCV2 positive by PCR. Phylogenetic trees constructed by both neighbor-joining and Bayesian Inference yielded similar topology of the ORF2 sequences. Thai PCV2 comprise four clusters: PCV2a (5.5%), PCV2b (29.41%), intermediate clade 1 (IM1) PCV2b (11.03%) and PCV2d (54.41%). Genetic shift of PCV2 in Thailand has occurred similarly to the global situation. The shift from PCV2b to PCV2d was clearly observed during 2013-2014. The viruses with genetically similar to the first reported PCV2 in 2004 have still circulated in Thailand. The first Thai PCV2b and PCV2d were closely related to the neighboring countries. The haplotype network analysis revealed the relationship of PCV2 in Thailand and other countries. These results indicate that genetic diversity of PCV2 in Thailand is caused by genetic drift of the local strains and intermittent introduction of new strains or genotypes from other countries. Genetic evolution of PCV2 in Thailand is similar to that occurs globally., (Copyright © 2017 Elsevier B.V. All rights reserved.)