Porcine Circovirus Type 3: Diagnostics, Genotyping, and Challenges in Vaccine Development.

Porcine circovirus (PCV) comprises four distinct species, namely, PCV1-4, with considerable differences between them, resulting in limited crossprotection. PCV2 inflicts substantial economic losses on the swine industry. PCV3 was found to have been circulating before its discovery in 2015. PCV3 is suspected of having a comparable impact to PCV2; however, its characterization studies are still underway. The symptoms of PCV3 infection are similar to those of PCV2 infection. However, PCV2 and PCV3 share a maximum amino acid identity of only 37%, which partially explains the inadequacy of the PCV2 vaccine in protecting against PCV3 infection. Swift measures must be taken to control PCV3, including vaccine development, as it also poses a threat to swine populations. This review synthesizes the recent findings on PCV3 in comparison with PCV2 and highlights the prevailing challenges encountered in vaccine development. Various strategies and innovative approaches to producing PCV3 vaccines, such as using RNA particle technology and baculovirus vectors, are also discussed. Addressing research gaps in diagnostic methods, viral isolation, and vaccine development is crucial to controlling this virus, which poses a threat to swine populations.