Recent Progress on Epidemiology and Pathobiology of Porcine Circovirus 3

Abstract

The recently discovered porcine circovirus 3 (PCV3) belongs to the Circovirus genus of the Circoviridae family together with the other three PCVs, PCV1, PCV2, and PCV4. As reported, PCV3 can infect pig, wild boar, and several other intermediate hosts, resulting in single or multiple infections in the affected animal. The PCV3 infection can lead to respiratory diseases, digestive disorders, reproductive disorders, multisystemic inflammation, and immune responses. Up to now, PCV3 infection, as well as the disease caused by PCV3, has been reported in many swine farms worldwide with high positive rates, which indicates that the virus may be another important pathogen in the swine industry. Therefore, we reviewed the current progress on epidemiology and pathobiology of PCV3, which may provide the latest knowledge of the virus and PCV3-related diseases.

Advances in Crosstalk between Porcine Circoviruses and Host

“…PCVs are non-enveloped DNA viruses with a diameter of about 20 nm, belonging to the genus Circovirus in the family Circoviridae [ 1 , 2 , 3 , 4 ]. The genome of PCV is a single-stranded, positive-circular DNA of about 1.7–2.0 kb in length, encoding structural protein capsid (Cap), replicase (Rep), and/or other non-structural proteins ( Figure 1 A) [ 1 , 2 , 3 , 4 ]. The genome of PCV2 contains at least 11 open reading frames (ORFs), of which five ORFs encode proteins with known or partially known functions.…”

“…Porcine circoviruses (PCVs) are viruses isolated from diseased pigs or porcine cells, which include PCV1 to PCV4 to date [ 1 , 2 , 3 , 4 ]. PCV1 was first identified and isolated from porcine kidney cells and considered contamination due to its non-pathogenic characteristics in vivo and in vitro [ 5 ].…”

“…PCVD/PCVAD includes PMWS, porcine respiratory disease complex (PRDC), porcine dermatitis and nephropathy syndrome (PDNS), enteric disease, and reproductive disease [ 4 ]. PCV3 was first detected in domestic pigs with cardiac and multi-organ inflammation in 2015–2016 in the USA and then in other countries [ 3 , 7 ]. Further studies showed that PCV3 infection could induce PDNS, respiratory diseases, diarrhea, and reproductive failure [ 8 , 9 ].…”

“…PCV2 was recognized as one of the most critical economic viruses in the swine industry. Although the pathogenesis of PCV, especially PCV3 and PCV4, remains to be clarified, the widespread distribution of PCV2, PCV3, and PCV4 in pigs (including diseased and healthy pigs), wild boar, and/or other animals has been confirmed [ 3 , 4 , 15 , 16 , 17 , 18 , 19 ]. Notably, both PCV2 and PCV3 are closely related to bat circovirus in genome and protein levels, whereas PCV4 has higher homology to mink circovirus [ 1 , 3 , 20 ], which suggests that the host spectrum of PCVs may be broader than what we have already determined.…”

“…Although the pathogenesis of PCV, especially PCV3 and PCV4, remains to be clarified, the widespread distribution of PCV2, PCV3, and PCV4 in pigs (including diseased and healthy pigs), wild boar, and/or other animals has been confirmed [ 3 , 4 , 15 , 16 , 17 , 18 , 19 ]. Notably, both PCV2 and PCV3 are closely related to bat circovirus in genome and protein levels, whereas PCV4 has higher homology to mink circovirus [ 1 , 3 , 20 ], which suggests that the host spectrum of PCVs may be broader than what we have already determined. Therefore, it is still urgent and necessary to prevent and control the transmission and infection of PCVs in pigs, which depends on an in-depth understanding of the interaction between the virus and the host.…”