PCV3 in Thailand: Molecular epidemiology and relationship with PCV2

Abstract

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.

Molecular detection and phylogenetic analysis of porcine circovirus type 3 in Tibetan pigs on the Qinghai-Tibet Plateau of China

“…Several studies have previously shown that PCV3 has spread widely around the world, infecting mainly domestic pigs [11,12,16,17,[25][26][27]. This virus has also been shown to have high prevalence in wild boars in Germany [12] and Sardinia [25].…”

“…Currently, PCV3 can be divided into at least three clades (PCV-3a, PCV-3b and PCV-3c) based on evolutionary analysis of cap genes [11]. After the first report of PCV3 infection in the United States [7], its prevalence was determined in pigs suffering from clinical digestive or respiratory diseases in several other countries, including Germany [12], Korea [13], Sweden [14], China [15], Russia [16] and Thailand [17]. However, to date, no epidemiological study of PCV3 has been conducted with healthy pigs as a control group on the same farm.…”

Genotype Shift of Malaysian Porcine Circovirus 2 (PCV2) from PCV2b to PCV2d within a Decade

“…Porcine circovirus 3 (PCV3) and porcine circovirus 4 (PCV4) are two newly emerging viruses in the swine industry, first reported in 2016 and 2019 [ 6 , 7 ]. Reports of co-infection of PCV2 with these two relatively new PCV species have surfaced, with the clinical implication of their co-existence in the swine host still being debated [ 85 , 86 , 87 , 88 ]. PCV3-positive clinical samples were frequently found to be co-infected with PCV2 with co-infection rates of 27.6% to 69.74%, suggesting the common occurrence of mixed PCV2 and PCV3 infection [ 86 , 89 , 90 ].…”

Detection of Porcine Circovirus Type 3 in Serum, Semen, Oral Fluid, and Preputial Fluid Samples of Boars

“…PCV3 can be detected in pigs of different ages and causes clinical symptoms similar to those caused by PCV2. PCV3 infection can cause several clinical-pathological outcomes, such as respiratory disease, digestive disorders, congenital tremors, rectal prolapse, reproductive problems, and multisystemic inflammation, which are no less harmful to the pig industry than PCV2 [ 16 ]. However, the transmission characteristics of PCV3 in infected pigs are unclear.…”