Identification and genetic characterization of porcine circovirus 3 on pig farms in Serbia.

Backgroud: The presence of PCV3 genome has been detected in pigs affected by different clinical and pathological conditions as well as in healthy animals. Its presence has been reported in many countries of North and South America, Asia and Europe. However, there is no evidence of the presence and genetic characteristics of PCV3 in many European countries and especially the countries of the Balkan Peninsula.

Purpose: The major objective of this study was to investigate the presence and obtain further genetic characterization of PCV-3 in the pig populations in Serbia.

Methods: To demonstrate the presence of PCV-3 DNA a conventional PCR assay was performed. The samples where no PCR product was observed (n=32), were further tested with a real-time PCR assay. The six PCR samples that were strongly positive for PCV-3 were subjected to amplification and sequencing of their entire cap genes and complete viral genome.

Results: We report on the first identification, genetic diversity and potential association in pathogenesis of some systemic and respiratory swine diseases of PCV-3 in Serbia.

Conclusion: The results imply that PCV-3 circulates widely in the pig population and has a high similarity with previously reported isolates. Detected PCV-3 can be associated with some swine systemic and respiratory diseases but these associations are strongly influenced by the clinical or pathological condition of the animals. Our findings demonstrate that there are certain PCV-3 loads in pigs suffering from active PRRSV infection, Glässer's disease, APP pleuropneumonia, pneumonic pasteurellosis and PRDC; however, the significance of this viral load, as well as the mechanism by which PCV-3 may act as a secondary agent in aggravating the severity during co-infections of these pathogens, requires further research.