The prevalence and genetic characteristics of porcine circovirus type 2 and 3 in Korea

Abstract

BackgroundPorcine circovirus-associated diseases (PCVAD), caused by porcine circovirus type 2 (PCV2), threaten the pig industry worldwide. Five genotypes of PCV2 were recently identified: PCV2a, PCV2b, PCV2c, PCV2d and PCV2e. In addition, a novel porcine circovirus from a case of a sow with dermatitis, nephropathy syndrome and reproductive failure has been identified based on metagenomic analysis and classified as porcine circovirus type 3 (PCV3). Therefore, the current study was conducted to determine the prevalence and genetic characteristics of PCV2 and PCV3 in clinical samples.ResultsA total of 471 samples (161 tissue samples of lungs and lymph nodes from 34 farms and 310 serum samples from 47 farms) were tested for PCV2. Among them, 171 samples from 59 farms that had been positive for PCV2 were genotyped. Another 690 samples (296 tissue samples of lungs and lymph nodes from 91 farms, 108 samples of aborted foetuses from 26 farms, and 286 serum samples from 47 farms) were tested for PCV3. Based on PCV2 genotyping results, PCV2d was the most prevalent genotype (107 of 171 samples), and co-infections with combinations of PCV2a, 2b and 2d were identified in 48 samples from 17 farms. A total of 14 samples from 11 farms were also positive for both PCV2 and PCV3. For PCV3, 57 samples (9.8%) from 32 farms (23.2%) were positive. Among the 108 aborted foetuses from 26 farms, only 2 samples were positive for PCV3. Based on sequence comparisons, PCV2d shares 89.6–91.0% and 93.2–94.3% homology with PCV2a and PCV2b, respectively; 98.6–100% homology is shared among PCV2d strains. The PCV3 strains identified in this study share 98.0–99.5% homology.ConclusionsOur study concludes that PCV2d has become the most predominant genotype in Korea. PCV3 was also identified in clinical samples, though no significant association with clinical symptoms was observed in PCV3-positive cases.

Genetic diversity and prevalence of porcine circovirus type 3 (PCV3) and type 2 (PCV2) in the Midwest of the USA during 2016–2018

“…Also, higher PCV3 infection rates have been reported in animals with digestive and respiratory diseases (Qi et al, ). However, not all studies support the putative role of PCV3 as a major threat to swine health (Franzo et al, ; Kim et al, ; Saporiti et al, ). Prevalence data presented here do not support the positive association of PCV3 infection with enteric‐disease‐causing or respiratory‐disease‐causing viral infections.…”

Does porcine circovirus type 3 (PCV3) interfere with porcine circovirus type 2 (PCV2) vaccine efficacy?

“…Biological properties of PCV3 and the way the virus interacts with the immune system of pigs are still not known. However, PCV3 was identified in lymphoid tissue and lungs of clinically affected pigs (Chen et al, ; Fu et al, ; Kedkovid et al, ; Kim et al, ; Li, Qiao, Sun, & Tian, ; Palinski et al, ; Ye et al, ). Thus, PCV3 seems to have similar cellular tropism as PCV2 and can also have similar immunocompromising characteristics.…”

“…The lack of concurrent PCV2 and PCV3 viremia in almost all pigs from 11 farms does not exclude existing co‐infection of some tissues or transient viremia that was not detected in this study. There are several reports about detection of concurrent PCV2 and PCV3 infections in tissue samples (Chen et al, , ; Fu et al, ; Kim et al, , ; Ku et al, ; Li et al, ; Zhang et al, ), but only one of them described also PCV2 and PCV3 concurrent viremia (Kim et al, ). In the latter study, concurrent infections with PCV2 and PCV3 were found only in 1.9% (6 out of 310) and 1.4% (4 out of 286) serum samples (Kim et al, ).…”

Self-assembly into virus–like particles of the recombinant capsid protein of porcine circovirus type 3 and its application on antibodies detection

“…PCV2 can cause clinical symptoms including postweaning multisystemic wasting syndrome (PMWS), pneumonia, porcine dermatitis, nephropathy syndrome (PDNS), and reproductive failure (Madson and Opriessnig 2011). PCV3 was identified as a new member of PCV in 2015 (Palinski et al 2017), additional studies showed that PCV3 appeared in other countries (China, Poland, Brazil, Korea, Denmark, Italy and Spain) (Franzo et al 2018a;Kim et al 2018b;Shen et al 2018;Stadejek et al 2017;Tochetto et al 2018). Specifically, the existence of PCV3 in pigs can be traced back to as early as 1996 in China according to early studies .…”