• Korean Journal of Veterinary Service
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• v.30 no.1
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• pp.85-93
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• 2007

The purpose of this study was to investigate the infection situation of several diseases (post-weaning atrophic pigs) such as porcine reproductive and respiratory syndrome (PRRS) in swine breeding complex in Jeonbuk-Iksan. From February to October in 2006, a total of 28 swine samples (6-10 week old) were collected from 6 farms and examined by polymerase chain reaction(PCR) and clinical signs. In the rate of single infection, pneumonia was top (32.1%), followed by salmonellosis (14.2%)and Glasser's disease (10.7%) and double infection pneumonia/Glasser's disease (17.8%) was detected. PCR was detected of PCV 2 from 28 (100.0%) and PPV 6 (21.4%), PRRS PORF6 10 (35.7%) and POR7 11 (39.2%), but HC and AD was not detected. The results suggest that PCV 2 is complex infection PRRS, PPV and bacterial disease.

• Korean Journal of Veterinary Service
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• v.36 no.2
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• pp.139-145
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• 2013

Porcine respiratory disease complex (PRDC) continues to be a significant economic problem to the swine industry. In order to elucidate the etiology of PRDC including porcine circovirus type 2 (PCV2), porcine reproductive and respiratory disease syndrome virus (PRRSV), swine influenza virus (SIV), Mycoplasma hyopneumoniae (MH), Pasteurella multocida (PM) and Actinobacillus pleuropneumoniae (APP) in Namwon, the 455 lung samples were randomly collected from slaughtered pigs, examined gross lesions indicative of respiratory disease of lung and classified the lung lesion according to the severity of lung lesions. Two hundred pigs lung tissues with pneumonic lesions were examined for pathogen by PCR. As a result, the numbers of pneumonic lesions were 357 (78.5%), mean pneumonic score ($mean{\pm}SD$) was $2.03{\pm}0.90$ and the highest gross lesion according to stages was 1 (11~20%). In detection of pathogens, PCV2, PRRSV, SIV, MH, APP and PM were positive in 76.5%, 5.0%, 6.0%, 9.0%, 4.5% and 6.0%, respectively and PCV2-MH was the most detected causative pathogens of PRDC in co-infection. In the serological test for PRRSV, PCV2, MH, APP2, APP5, HP and PM, showed high antibody positive rates 93% or more.

• Journal of Life Science
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• v.24 no.10
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• pp.1118-1124
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• 2014

Porcine respiratory disease complex (PRDC) is a common respiratory disease in nursery and grow-finishing pigs. A complex of viral and bacterial agents is known to be involved in the etiology of PRDC. The purpose of this study was to investigate common etiologic agents associated with PRDC in the field and compare detection methods for identifying these agents. To understand the mechanism of polymicrobial infection in PRDC, changes in the expression of cytokines were investigated. In 461 pig samples examined, most of the affected pigs ranged from 3 to 10 weeks old (73.4%), and 348 (75.4%) samples were confirmed as polymicrobial infection. Of the polymicrobial-infected cases, two (50.3%), three (32.2%), four (13.8%), five (3.2%), and six (0.5%) agents were detected. Two- or three-agent infections were the most common, with PRRSV/PCV-2 (44.6%) the most common two-agent infection. PRRSV/PCV-2/H. parasuis (11.0%) was the most common three-agent infection. Comparison of two detection methods (PCR and IHC) in the polymicrobial cases showed that 78.4% were PCV-2 positive with the PCR method, and 26.2% were PCV-2 positive with IHC. SIV was 7.8% by the PCR method and 3.7% positive by the IHC. This result indicates that the PCR method is more useful than IHC for detecting causative agents in PRDC. In the analysis of cytokines in the two- and three-agent infected samples, interleukin (IL)-$1{\alpha}$, IL-2, IL-4, IL-6, IL-10, and INF-${\alpha}$ showed the same expression pattern. All cytokines were suppressed, except IL-6. These findings indicate that changes in cytokine expression could be used to understand the mechanism of polymicrobial infection in PRDC.

• Journal of Microbiology and Biotechnology
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• v.18 no.10
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• pp.1709-1716
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• 2008

The porcine reproductive and respiratory syndrome Virus (PRRSV) is an infectious disease that causes abortions and respiratory disorders in swine. In this study, the interaction between PRRSV and porcine dendritic cells generated from $CD14^{+}$ monocytes in the presence of GM-CSF and IL-4 was examined. As a result, it was shown that immature and mature dendritic cells can be productively infected with PRRSV. When the expression of surface MHC molecules on infected dendritic cells was determined, MHC classes I and II were found to be downregulated when compared with un infected dendritic cells. With the exception of the IL-4 and IFN-$\gamma$ cytokines, the induction of the IL-10, IL-12, and TNF-$\alpha$ cytokines all increased in dendritic cells infected with PRRSV. A mixed lymphocyte reaction showed that peripheral blood mononuclear cells cocultured with PRRSV-infected dendritic cells were less stimulated than peripheral blood mononuclear cells cocultured with dendritic cells treated with PBS, LPS, or UV-inactivated PRRSV. Therefore, these results suggest that PRRSV would appear to modulate the immune stimulatory function of porcine dendritic cells.

• Korean Journal of Veterinary Service
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• v.24 no.2
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• pp.127-132
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• 2001

Porcine circoviruses(PCV) are the smallest nonenveloped DNA viruses containing a unique single-stranded circular genome. No recognized link was found between PCV infection of pig and disease. But the PCV consistently identified from postweaning multisystemic wasting syndrome(PMWS) and researches indicate that there are strong relationships between PCV and PMWS. Clinical signs were emaciation, dyspnea, high fever with normal appetite. Necropsy findings showed respiratory disease complex lesion and lymph node anomalities. An indirect-immunofluorescent antibody procedure was used to assay swine sera for the presence of PCV atibodies. Antibodies against PCV were found in an average of 20% of the samples tested. The PCV DNA was amplified from lymph nodes collected from pigs. PCV specific primers were successfully amplified PCV DNAs. Further studies are needed to determine the possible role this virus might have in disease.

• Korean Journal of Veterinary Service
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• v.34 no.4
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• pp.313-320
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• 2011

The purpose of this study was to investigate association with gross lesions and causative pathogens of porcine respiratory disease complex (PRDC) including porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), Mycoplasma hyopneumoniae (MH), Pasteurella multocida (PM), Actinobacillus pleuropneumoniae (APP), Haemophilus parasuis (HP) in slaughtered pigs. A total of 1,200 lung samples were collected randomly from slaughtered pigs in Korea during August of 2010 through July of 2011. The gross lesions were classified according to the six stages (0, 1~10, 11~20, 21~30, 31~40 and ${\geq}41$, unit=%) and 48 samples from each stage were selected to detect viral and bacterial pathogens. The results according to the six stages were 100 (8.3%), 259 (21.6%), 326 (27.2%), 213 (17.8%), 144 (12.0%) and 158 (13.2%) cases, respectively. Prevalence of pneumonia according to season was 87.0~96.7% and the highest prevalence was in spring. In detection of pathogens by PCR, 53 samples were not detected any causative pathogens of PRDC. PCV2, PRRSV, SIV, MH, PM, APP serotype 2, APP serotype 5 and HP were positive in 45.5%, 12.5%, 10.4%, 60.1%, 1.7%, 13.9%, 12.2% and 15.6%, respectively. In co-infection, PCV2-MH was the most detected causative pathogens of PRDC. The detection rate of PCV2 and PRRSV was the highest in spring, of SIV, MH and HP was in winter. The detection rate of APP-2 and APP-5 had no seasonal prevalence. The more severe gross lesions increased, the higher the detection rate showed.

• Korean Journal of Veterinary Service
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• v.42 no.4
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• pp.201-216
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• 2019

Porcine reproductive and respiratory syndrome (PRRS) is characterized by reproductive failure in sows and respiratory distress in all age pigs. Porcine respiratory disease complex (PRDC) is a disease caused by opportunistic bacterial infection secondary to a weakened immune system by a preceding respiratory infection. In this study, we tried to compare the immune responses in PRRS and PRDC groups to clearly characterize the disease severity. Eighty-five pigs were infected with various Korean field PRRS virus strains. Infected animals were classified into PRRS (n=32) and PRDC (n=53) groups based on lung lesions such as interstitial pneumonia, suppurative pneumonia, and pleuropneumonia. The immune cell population of bronchoalveolar lavage cells (BALc) was evaluated on 14 and 28 days post infection (dpi) and PMBC cytokine expression was measured on 0, 3, 7, 14 dpi to investigate early inflammatory reactions. Pulmonary lesion severity was negatively correlated with alveolar macrophage (AM) in both PRRS and PRDC groups on 14 and 28 dpi. AM in BALc was less populated in PRDC group on 28 dpi compared to PRRS group. AM in BALc was significantly less populated in PRDC group on 28 dpi compared to 14 dpi. In addition, cytotoxic T lymphocyte (CTL) in BALc was higher populated in PRDC group on 14 dpi and 28 dpi compared to PRRS group. In the case of PBMC cytokine TNF-α, IFN-α, IL-1β, IFN-γ, FoxP3, and IL-2, the PRRS group showed higher expression than the PRDC group on 7 dpi, 14 dpi, 7 dpi, 14 dpi, 14 dpi, and 14 dpi, respectively. On the other hand, in the case of IFN-β, IL-6, IL-8, IL-4, and IL-17, the PRDC group showed higher PBMC cytokine expression at 14 dpi, 7 dpi, 14 dpi, 3 dpi, and 3 dpi, respectively, than the PRRS group. Based on these results, our study could characterize differential immune responses in pigs with PRRS or PRDC.

• Korean Journal of Veterinary Service
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• v.34 no.2
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• pp.133-138
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• 2011

The prevention of porcine respiratory disease complex (PRDC) is very important because of its high infection-rates in the swine farms and the economic impact in swne industry in Korea. To control the prevalence of PRDC, it is important to know about infection patterns of it. Therefore, this study aimed to investigate the infection patterns of PRDC in the northern area of Gyeongsangnam-do. To this end, the infection of porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), Actinobacillus pleuropneumoniae (APP), Mycoplasma hyopneumoniae (MH), and Swine influenza virus (SIV) were examined using 120 pig lung tissues by PCR analysis. As a result, single pathogen positive specimens were 25.0% and the others (75.0%) were turned out to be PRDC with at least two pathogens. Among PRDCs, 50 specimens (41.7%) was infected with PRRSV, PCV2, MH and SIV. Ten specimens (8.3%) showed triple infections of PRRSV, PCV2 and MH. Double infected specimens for PRRSV and PCV2 were 10 (8.3%), and for PCV2 and APP were 20 (16.7%).

• Korean Journal of Veterinary Service
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• v.41 no.3
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• pp.203-210
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• 2018

Pasteurella multocida is an opportunistic organism that plays a significant role in porcine respiratory disease complex (PRDC). In the current study, we provide nationwide information of P. multocida isolates from pneumonic lungs of slaughter pigs by determining their prevalence, subspecies, biovars, capsular types, virulence-associated genes, and minimum inhibitory concentrations. P. multocida was the second most frequently confirmed (19.2%) bacterial pathogen and most of the isolates (88.9%) showed simultaneous infection with other respiratory pathogens, especially Mycoplasma hyopneumoniae (63.3%, P<0.001) and porcine circovirus type 2 (53.3%, P=0.0205). Of 42 isolates investigated, 41 (97.6%) were identified as P. multocida subspecies multocida, and only one isolate was identified as subspecies septica (biovar 5). All the isolates were capsular type A and the most prevalent biovar was biovar 3 (40.5%), followed by biovar 2 (31.0%). Comparing virulence-associated genes and biovars, all biovar 2 isolates exhibited $hgbB^-pfhA^+$ (P<0.001); all biovar 3 (P=0.0002) and biovar 13 (P=0.0063) isolates presented $hgbB^+pfhA^-$. Additionally, all biovar 2 (P=0.0037) isolates and most of biovar 3 (P=0.0265) isolates harbored tadD. P. multocida showed the highest resistance levels to oxytetracycline (73.8%), followed by florfenicol (11.9%). Continuous monitoring is required for surveillance of the antimicrobial resistance and new emerging strains of P. multocida in slaughter lines.

• Journal of Veterinary Clinics
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• v.22 no.4
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• pp.365-370
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• 2005

Enzootic pneumonia caused by Mycoplasma hyopneumoniae is responsible for major economic losses in pig herds of world wide. Mycoplasma hyopneumoniae can also act as a primary pathogen of porcine respiratory disease complex followed by bacterial or viral infection. This study was carried out to investigate the prevalence of mycoplasmal pneumonia of slaughtered pigs in Jeju for two years. The lungs and sera of 214 cases were examined for gross and microscopic lesions of the lungs, immunohistichemistry test for Mycoplasma hyopneumoniae antigen and enzyme-linked immunohistichemistry assay (ELISA) for serum antibody titer. Pulmonary consolidation was observed in the lungs of 163 pigs $(76.1\%)$ with average gross lesion score of $6.0\%$., Bronchointerstitial pneumonia was most frequently observed $(78.5\%)$. The incidence of pulmonary consolidation was decreased in vaccinated pigs compared to that of non-vaccinated pigs. The rate of consolidation in the lungs was significantly decreased in the vaccinated pigs (P<0.05). Antigen of Mycoplasma hyopneumoniae was identified by immunohistichemistry test in the lungs of 174 pigs $(81.3\%)$. ELISh antibodies to Mycoplasma hyopneumoniae were detected in 154 pigs $(72.0\%)$. These results showed the prevalence of swine pneumonia and the incidence of Mycoplasma hyopneumoniae in slaughtered pigs of Jeiu province. We expect that these results would be helpful for the control of swine mycoplasmal pneumonia and porcine respiratory disease complex in Jeju.