• Korean Journal of Veterinary Service
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• v.45 no.2
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• pp.87-99
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• 2022

A novel porcine circovirus 4 (PCV4) was recently emerged in Chinese and Korean pig herds, which provided epidemiological situation where three pathogenic PCVs, PCV2, PCV3, and newly emerged PCV4, could co-infect pig herds in these countries. In this study, a new triplex quantitative real-time polymerase chain reaction (tqPCR) method was developed for the rapid and differential detection of these viruses. The assay specifically amplified each viral capsid gene, whereas no other porcine pathogenic genes were detected. The detection limit of the assay was below 10 copies/µL and the assay showed high repeatability and reproducibility. In the clinical evaluation using 1476 clinical samples from 198 Korean pig farms, the detection rates of PCV2, PCV3 and PCV4 by the tqPCR assay were 13.8%, 25.4%, and 3.8%, respectively, which were 100% agreement with those of previously reported monoplex qPCR assays for PCV2, PCV3, and PCV4, with a κ value (95% CI) of 1 (1.00~1.00). The prevalence of PCV2, PCV3, and PCV4 at the farm levels were 46.5%, 63.6%, and 19.7%, respectively. The co-infection analysis for tested pig farms showed that single infection rates for PCV2, PCV3, and PCV4 were 28.8%, 44.4%, and 9.6%, respectively, the dual infection rates of PCV2 and PCV3, PCV2 and PCV4, and PCV3 and PCV4 were 12.6%, 3.5%, and 5.1%, respectively, and the triple infection rate for PCV2, PCV3, and PCV4 was 1.5%. These results demonstrate that three pathogenic PCVs are widely spread, and their co-infections are common in Korean pig herds, and the newly developed tqPCR assay will be useful for etiological and epidemiological studies of these pathogenic PCVs.

• Korean Journal of Veterinary Research
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• v.51 no.1
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• pp.7-14
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• 2011

This study was focused on the genotyping and quantification of Porcine circovirus type 2 (PCV2) in thirty PCV2-positive pigs with different clinical symptoms (PCV2-infected without wasting, PCV2-infected with wasting, PCV2-infected with wasting and lymphoid depletion). The quantity of PCV2 DNA in diverse tissues was significantly differed among these groups. (One-way ANOVA test, p<0.001) Interestingly, PCV2-DNA load in tissues of PCV2-infected pigs without wasting and PCV2-infected pigs with wasting and lymphoid depletion were not significantly differed (p = 0.38), while they were all significantly higher when compared with PCV2-infected pigs with wasting-only. PCV2 DNA quantity in tissues was significantly higher in PCV2a and 2b co-infected pigs compared to the PCV2b only-infected pigs (Wilcoxon test, p = 0.039). The PCV2a and 2b co-infected pigs had increased wasting and lymphoid depletion rate but it was not statistically significant. Therefore, this cross-sectional study suggested that PCV2 DNA load in tissues was diverse by clinical and histological findings. Furthermore, co-infection of PCV2a and 2b affected to the PCV2 DNA load in tissues with increased rate of wasting and lymphoid depletion.

• Korean Journal of Veterinary Service
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• v.27 no.2
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• pp.139-146
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• 2004

This study was carried out to investigate the prevalence of pocine circovirus type 2(PCV2) infection and post-weaning multi systemic wasting syndrome(PMWS) of swine in Gyeongbuk province from June to December in 2003. Gyeongbuk Veterinary Service Laboratory had tested PCV1 and PCV2 by the PCR method against 210 infected pigs of 105 farms, which were requested diagnosis of disease and investigate compositive infections with bacterial disease. The following results were obtained; 1. Among 210 pigs, The pigs infected with PCV1 were 134(63.8%) heads and with PCV2 were 143(68.1%) heads. 2. Using PCR, the rate of PCV1 infection of 105 farms which were requested of diagnosis of disease is positive in 75(71.4%) farms and 78(74.3%) farms were positive in PCV2, and compositive infections of PCV1 and PCV2 were 75(71.4%) farms. 3. According to age of requested pig, the frequency of PCV infection rate was following, the pig under 4 weeks of age were 28.6% in PCV1 and PCV2, respectively, and the pig of 4-7 weeks of age were 58.6% in PCV1 and PCV2, respectively. The pig of 8-11 weeks of age were 73.1% in PCVl and 74.6% in PCV2, the pig of 12-18 weeks of age were 80.9% in PCV1 and 88.1% in PCV2. 4. In the distribution of compositive infection with bacterial disease related to PCV2 among requested samples, PCV2 infection was 39.7% in 78 cases, two kinds of compositive infection was 38.5%, three kinds of compositive infection was 18.1% and four kinds of complex infection was 3.9%.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.259-268
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• 2004

Porcine circovirus type 2 (PCV-2) has been associated with various disease in pigs worldwide including postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS). In this study, monoclonal antibodies (MAbs) against PCV were produced, characterized and applications of MAbs as diagnostic reagents were described. Spleen or lymph node cells from BALB/c mouse immunized respectively with PCV-1, PCV-2 or expressed PCV-2/ORF2 proteins in baculovirus were fused with SP2/0 myeloma cells using polyethylene glycol (PEG) and hybridoma cells producing PCV-1 or PCV-2-specific antibody were screened by an indirect immunofluorescence (IIF) test. A total of fifteen MAbs were produced against PCV. Six MAbs were PCV-1-specific and nine were PCV-2-specific. All PCV-1-specific MAbs reacted with only PCV-1 and all PCV-2-specific MAbs were reactive with only PCV-2 by IIF test. None of the MAbs was reactive with porcine reproductive and respiratory syndrome virus (PRRSV), porcine parvovirus (PPV), porcine rotavirus (PRV), and transmissible gastroenteritis virus (TGEV). Some PCV-2-specific MAbs recognized the PCV-2 infected porcine tissues by IIF or immunohistochemistry (IHC) assay. From this experiment, it was confirmed that MAbs produced in this study were PCV-specific and could be used as reliable diagnostic reagents for PCV-1/PCV-2 detection and differentiation.

• Journal of Animal Science and Technology
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• v.65 no.4
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• pp.698-719
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• 2023

Postweaning multisystemic wasting syndrome (PMWS) is caused by a systemic inflammation after porcine circovirus type 2 (PCV2) infection. It was one of the most economically important pathogens affecting pig production worldwide before PCV2 vaccine was first introduced in 2006. After the development of a vaccine against PCV2a type, pig farms gradually restored enormous economic losses from PMWS. However, vaccine against PCV2a type could not be fully effective against several different PCV2 genotypes (PCV2b - PCV2h). In addition, PCV2a vaccine itself could generate antigenic drift of PCV2 capsid. Therefore, PCV2 infection still threats pig industry worldwide. PCV2 infection was initially found in local tissues including reproductive, respiratory, and digestive tracks. However, PCV2 infection often leads to a systemic inflammation which can cause severe immunosuppression by depleting peripheral lymphocytes in secondary lymphoid tissues. Subsequently, a secondary infection with other microorganisms can cause PMWS. Eleven putative open reading frames (ORFs) have been predicted to encode PCV2 genome. Among them, gene products of six ORFs from ORF1 to ORF6 have been identified and characterized to estimate its functional role during PCV2 infection. Acquiring knowledge about the specific interaction between each PCV2 ORF protein and host protein might be a key to develop preventive or therapeutic tools to control PCV2 infection. In this article, we reviewed current understanding of how each ORF of PCV2 manipulates host cell signaling related to immune suppression caused by PCV2.

• Journal of Veterinary Clinics
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• v.27 no.6
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• pp.704-712
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• 2010

Porcine circovirus-2 (PCV2) has been implicated in many clinical diseases/syndromes that are now referred to as PCV-associated diseases (PCVAD). Due to significant economic losses caused by PCVAD, many swine operations have launched extensive monitoring programs for PCV2. Traditional serum sampling is, however, rather expensive and laborious, hampering effective large scale pathogen surveillance. A field-based longitudinal study was conducted to assess the utility of pen-based oral fluid sample as an alternative to serum for herd PCV2 testing. Six pens (25 pigs/pen) at each of 3 different sites were used in the study. One oral fluid and 5 random serum samples per pen were collected at 3, 5, 8, 12, and 16 weeks of age, and the sera were pooled by pen for testing. All samples were tested for PCV2 by real-time PCR and for antibodies by indirect fluorescent antibody test (for both anti-PCV2 IgG and IgA) and 3 ELISA assays (blocking ELISA, indirect ELISA, and IgG/IgM sandwich ELISA). PCV2 DNA was detected in oral fluid samples sporadically until 8 weeks and in all pens at 16 weeks. PCV2-specific IgG was detected in oral fluid samples at 3 weeks and persisted until 5 to 8 weeks in all sites. Anti-PCV2 IgG and IgA were detectable in oral fluid samples collected at 16 weeks from all of the pens at 1 site. The detection of PCV2 and anti-PCV2 antibody in oral fluid samples correlated positively with results on pooled sera, suggesting that oral fluids can be a cost-effective alternative to serum for herd monitoring of PCV2 infection.

• Korean Journal of Veterinary Service
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• v.46 no.4
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• pp.315-324
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• 2023

This study was carried out to investigate the genotypic diversity of PCV2 and co-infection of PCV3 in the hilar lymph nodes of 700 randomly-selected slaughter pigs. Fourteen samples per each farm were obtained from 50 farms between February and August in 2022. Of the 50 farms, 44 farms that had been positive for PCV2 by RT-PCR were genotyped. As a result of PCV2 genotyping, positive rate of PCV2 DNA was 62.3% (436/700). Among the PCV2 DNA-positive samples, positive rate of a single PCV2 genotype was 79.1% (345/436), while multiple PCV2 genotypes were only detected in 20.9% (91/436). Of the 436 single infection cases, PCV2d genotype was most prevalent. Positive rates of PCV2 and PCV3 were 53.6% and 26.0% at the sample level, 5.1% and 8.0% at the farm level, respectively. And the co-positive rate of two viruses was 8.7% (61/700) at the sample level, 62.0% (31/50) at the farm level. These results demonstrate that PCV2 prevalence in slaughter pigs is very high and co-infection between different PCV2 genotypes and between PCV2 and PCV3 is relatively common. Therefore, genetic diversity and co-infection between other porcine circoviruses should be consistently monitored in the future.

• Korean Journal of Veterinary Service
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• v.32 no.1
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• pp.1-10
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• 2009

In order to obtain the genetic information of the Korean isolates of porcine circovirus 2 (PCV2), complete genomes of five isolates from Korean PCVD weaned pigs with wasting syndromes were sequenced and compared with those of other published PCV2 isolates. Of the five PCV2 isolates, four (1767 nucleotides) were classified into PCV2b, and one (1,768 nucleotides) was PCV2a. Moreover, it appeared that PCV2b is now the dominant genotype circulating in Korea herds. Total complete genomes of four PCV2b isolates shared $99.1{\sim}99.4%$ nucleotide sequence homology each other, and were only $95.4{\sim}96.2%$ similar to one PCV2a isolate. ORF2 genome of four PCV2b isolates shared over 99% nucleotide sequence and deduced amino acid sequence identity to each other. Nevertheless, those were much divergent with the PCV2a isolate of this study and ranged from $92.3{\sim}92.7%$ nucleotide homology and $91.9{\sim}92.3%$ deduced amino acid sequence homology, respectively. The amino acid sequence alignments of the putative capsid protein identified three major regions of amino acid heterogeneity at residues $59{\sim}91$, $121{\sim}136$ and $190{\sim}210$. Two of those correspond with dominant immunoreactive areas. Phylogenetic analysis based on the complete genome of PCV2 isolates showed that four PCV2b isolates of this study existed the closest relationship with European strains (Netherland, UK and France). One PCV2a isolate was closely related to Japan and North America strains.

• Korean Journal of Veterinary Service
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• v.28 no.3
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• pp.267-273
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• 2005

The present study was conducted to investigate the prevalence of PCV2 infection of the aborted pigs in Gyeongbuk province from April in 2004 to March in 2005. The prevalence of PCV1 and PCV2 infection was confirmed by the PCR method against 32 aborted pigs of 19 farms, which were requested of diagnosis of disease. Among 32 aborted pigs, abortions caused by PCVI were $7(21.9\%)$ heads and by PCV2 were $9(28.1\%)$ heads. Using PCR, the rate of PCV1 infection of 19 farms which were requested of diagnosis of disease is positive in $2(10.5\%)$ farms and $5(26.3\%)$ farms were positive in PCV2, and compositive infections of PCVI, PCV2 is $1(5.3\%)$ farms. Among 32 aborted the pigs, only PCV2 infection was one case $(3.1\%)$, compositive infections with abortion disease were 8 cases $(25\%)$, Compositive infections with abortion disease were most of the parvovirus infection $(84.2\%)$.

• Journal of Life Science
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• v.27 no.3
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• pp.283-288
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• 2017

Porcine circovirus type 2 (PCV2) is a notorious and ubiquitous virus in the swine industry. The susceptibility of the host to PCV2 infection is considered to be one factor associated with the dynamics of PCV2. The objective of this study was to verify the criteria for host susceptibility to PCV2, using blood parameters of post-weaned pigs naturally infected with the virus. The PCV2 DNA viral load, antibody titer, and leukopenia characteristics were measured in the serum extracted from the pigs at the 10th week. We classified the pigs into high (>5.0), intermediate (3.0 to 5.0), and low (<3.0) groups on the basis of the PCV2 viral load (log copies/ml), or as positive (${\leq}0.50$) and negative (>0.50) groups on the basis of antibody titer (sample-to-negative corrected ratio). Moreover, using these two categorized parameters, we suggested the criteria for classification into the susceptible and resistant groups. Statistical analyses revealed that pigs in the susceptible group had a significantly higher viral load (p<0.001) and negative antibody titer (p<0.001), as well as significantly lower leukocyte counts (p=0.018) and lower amounts of several leukocyte components (p<0.05), than pigs in the resistant group. We concluded that the susceptible group could be considered to have PCV2-induced leukopenia. Therefore, we suggest that the combined classifications of viral loads and anti-PCV2 antibodies can be used to determine PCV2-induced leukopenia in the subclinical PCV2 infection of post-weaned pig populations.