• 대한수의학회지
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• 제47권2호
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• pp.175-185
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• 2007

This study was carried out to investigate the pathogenesis and pathogenicity of the porcine circovirus type 2 (PCV2) Korean isolate from weaned pigs. Twenty four weaned pigs, PCV2, porcine reproductive and respiratory syndrome virus (PRRSV) and porcine parvovirus (PPV) antibodies free, were allocated to 4 groups (n = 6). Six pigs were inoculated intranasally with PCV2 alone, 6 with PCV2 and PRRSV, 6 with the combined PCV2/PRRSV/PPV inoculum, and 6 were remained as a uninoculated negative control. Pigs were killed 3 and 6 weeks after inoculation and tissue samples examined for gross and microscopic lesions and for the presence of PCV2 antigens and nucleic acids. Experimentally inoculated pigs were evaluated for 3 considerations: 1. development of postweaning multisystemic wasting syndrome (PMWS), 2. distribution of viral antigens by immunohistochemistry and polymerase chain reaction (PCR), and 3. cytokine mRNA levels in lymph nodes. Pigs inoculated with PCV2/PRRSV/PPV showed typical clinical signs, gross findings, and histopathologic characteristics of PMWS. In the PCV2/PRRSV/PPV inoculated group, the PCV2 antigen was widely distributed in various parenchymal organs such as brain, spinal cord, tonsil, lymph nodes, lung, heart, liver, kidney, spleen, and peyer's patch. Lymph node mRNA expression of IL-$1{\alpha}$, IL-2R and IL-8 was determined by real-time PCR. The pigs of PCV2/PRRSV and PCV2/PRRSV/PPV inoculation group, the mRNA expression was characterized by a decrease of IL-$1{\alpha}$, IL-2R and IL-8. The decrease of cytokine mRNA represent the state of T cell immuno-suppression in pig, and nicely support the evidence for the impairment of immune system in pigs with PMWS. In conclusion, PCV2 infection and some additional infectious causes such as PRRSV and/or PPV are warranted for the presence of PMWS in weaned pigs in Korea.

• 대한수의학회지
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• 제37권4호
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• pp.755-763
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• 1997

Recently new technologies for the establishment of high health herds are becoming efficient tools in the control of PRRS virus and secondary infections. Medicated early weaning(MEW) and nursery depopulation(ND) have shown to be one of the most successful procedures in the eradication and control of pathogens. Indirect evidence of the role of PRRSV in precipitating secondary infection comes from successful improvement in growth and in decreasing mortality on farms that have eliminated PRRSV through ND. Hence the present experiments were conducted in an effort to compare ND with MEW procedures as a means of eliminating PRRSV controlling secondary pathogens and improving performance of pigs in endemically infected swine herds. Following MEW and ND procedures practiced in the farms, some benefits obtained were as follows: 1. A decrease in PRRSV circulation in the nursery, but no entire elimination. 2. Decrease in the frequency of secondary bacteria and in the use of antibiotics. 3. Mycoplasma hyopneumoniae infection was prevented during the nursery stage. 4. ND protocol had a lower cost and management changes than MEW techniques. 5. Nursery performance was improved after the depopulation, cleaning and disinfection procedures, even though PRRSV still being cycled in the old nursery rooms. These studies revealed that the MEW and ND protocols are not always successful for PRRS virus elimination but it's great effect on control of secondary pathogens and improvement of performance make MEW and ND an efficient tools for the establishment of healthier and more efficient herds.

• 한국동물위생학회지
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• 제24권4호
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• pp.343-346
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• 2001

During the period of January to December 2000, a total of 3,505 swine sera was collected from 208 farms, which are located throughout country, for the diagnosis of porcine reproductive and respiratory syndrome(PRRS). The antibody to porcine reproductive and respiratory syndrome virus(PRRS) was tested by indirect immunofluorescent antibody(IFA) test. Of 208 farms tested, at least one or more than one pigs was positive for PRRSV antibody in 188(90.4%) farms. The overall seroprevalence of PRRSV antibody was 45.1% (1581/3505). Most pigs were infected with PRRSV at around 50- to 60-day old. The seroprevalence of antibody varied with age. The highest seroprevalence of PRRSV antibody was observed in the growing pigs at around 80-day old. About one-thirds of adult pigs including boar, gilt and sow were positive to PRRSV antibody. In many farms, the infection of PRRSV was chronic and confined to grower and/or finisher. However, antibody was detected from all production phase in some farms.

• 한국동물위생학회지
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• 제39권1호
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• pp.41-49
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• 2016

In the present study, fast and robust methods for the next generation sequencing (NGS) were developed for analysis of PRRSV full genome sequences, which is a positive sensed RNA virus with a high degree of genetic variability among isolates. Two strains of PRRSVs (VR2332 and VR2332-R) which have been maintained in our laboratory were used to validate our methods and to compare with the sequence registered in GenBank (GenBank accession no. EF536003). The results suggested that both of strains had 100% coverage with the reference; the VR2332 had the coverage depth from minimum 3 to maximum 23,012, for the VR2332-R from minimum 3 to maximum 41,348, and 22,712 as an average depth. Genomic data produced from the massive sequencing capacities of the NGS have enabled the study of PRRSV at an unprecedented rate and details. Unlike conventional sequence methods which require the knowledge of conserved regions, the NGS allows de novo assembly of the full viral genomes. Therefore, our results suggested that these methods using the NGS massively facilitate the generation of more full genome PRRSV sequences locally as well as nationally in regard of saving time and cost.

• 한국임상수의학회지
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• 제32권1호
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• pp.78-84
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• 2015

Although researches have highlighted the important role of enhanced farm biosecurity to reduce the severity and prevalence of diseases in livestock, to date there has been little study in Korea on farmers' adoption of biosecurity measures to control porcine reproductive and respiratory syndrome virus (PRRSV) infection. To mitigate the risk of PRRSV infection in pigs, the risk factors by which PRRSV is introduced in pig farms must be determined. The primary aim of this study was to investigate pig producers' perceptions about on-farm biosecurity practices. We also analyzed data obtained from a cross-sectional study on 196 farrow-to-finish farms conducted between March 2013 and February 2014 to identify risk factors for PRRSV infection at farm level. Standardized questionnaires with information about basic demographical data and management practices were collected in each farm by on-site visit of trained veterinarians. Farms were classified as negative or positive through the use of infection profiles that combined data on PCR positive pigs and serological testing including antibody titer, sero-conversion pattern at each age category, and vaccination status. Data on biosecurity practices, farm management and environmental characteristics were analyzed using multivariate ordinal logistic regression. Generally, the biosecurity level in the pig farms included in this study were insufficient to reduce/prevent the risk of PRRSV infection given the high pig density areas and the considerable extent of vehicle movement. Factors associated with PRRSV infection were those where owners used on-farm vaccination programs had a lower risk of infection (OR = 0.19, 95% CI 0.06-0.61). The results from the analysis may guide to tailor biosecurity measures in the reduction or prevention of PRRS to the specific circumstances of pig farms in different localities of the world. To the best knowledge of the authors, this is the first study to report information on the biosecurity practices currently implemented on Korean pig farms.

• 대한수의학회지
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• 제39권2호
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• pp.318-326
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• 1999

Respiratory pathogenic effects of several porcine reproductive and respiratory syndrome virus(PRRSV) isolates were examined in swine tracheal ring(STR) cultures by examining their effect on ciliary activity. One high and one low pathogenic PRRSV isolates were then selected and their pathogenicity investigated in 3-week-old conventional PRRSV-seronegative pigs. Ten pigs each were inoculated intranasally with the high or low pathogenic PRRSV isolate and 6 pigs were sham inoculated as negative controls. Two pigs each from the inoculated group and one pig each from negative control group were killed on 4, 7, 14, 21 and 28 days postinoculation(pI). At necropsy, degrees of gross lung lesion was determined. Turbinate, tonsil, trachea and lung samples were collected for virus isolation or histopathology. Gross lung lesions were observed mainly on 14 days PI with high and low pathogenic isolates inducing moderate diffuse and mild gross lung lesions, respectively. Inoculation of either the high or low pathogenic virus resulted in loss of cilia in ciliated epithelium of turbinates and trachea between 7 and 28 days PI. High pathogenic virus caused increased number of Goblet cells in the tracheal epithelial layer between 4 and 21 days PI whereas the low pathogenic virus did it between 14 and 28 days PI and with a lesser degree. Although both viruses produced interstitial pneumonia, the lesion was less severe with the low pathogenic virus. The isolation of high pathogenic virus from tissues and sera was earlier and more consistent than that of the low pathogenic virus. The agreement between in vitro and in vivo tests indicates that STR cultures may be used as a routine method to determine the respiratory pathogenicity of PRRSV isolates.

• 대한수의학회지
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• 제39권2호
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• pp.294-300
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• 1999

In this study PRRSV was isolated from serum of an infected pig and designated as CNV-1, ORF4 gene was sequenced, and the nucleotide sequence, deduced amino acid sequence and the amino acid sequence of the neutralizing domain was compared with other PRRSV Strains. ORF4 gene of the Korean isolate PRRSV CNV-1 was shown to be 537bp in length, which is the same as US strain ISU55 but 21bp longer than another US strain MN1b, and 15bp shorter than European strain LV. The homologies of the nucleotide sequences between the Korean isolate CNV-1 and the US strains ISU55, MN1b and European strain LV were 91.8%, 88.1%, 67.6%, respectively, and the homologies of the deduced amino acid sequences were 94.4%, 84.4%, 68.5%, respectively. The neutralizing domain of the CNV-1 was shown to be 36 amino acids in length which is the same as ISU55, MN1b, but 4 amino acids shorter than that of the neutralizing domain reported in LV. The homologies of the amino acid sequences of the neutralizing domain between the Korean isolate CNV-1 and the US strains ISU55, MN1b and European strain LV were 92.5%, 85%, 57.5%, respectively. The molecular characteristics of ORF4 gene of the Korean isolate PRRSV CNV-1 shown in this study suggests that the CNV-1 is genetically closer to the US strains. Also the wide variation of the neutralizing domain between the CNV-1 and LV suggests that there is substantial immunogenic variation between the two strains.

• 한국동물위생학회지
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• 제32권1호
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• pp.27-32
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• 2009

We studied the seroprevalence of four respiratory pathogens in Korean swine farms located in Chungnam, Chungbuk, Gyeongnam and Gyeongbuk provinces during the period of spring of 2007 to winter of 2008. Serological tests were performed using commercial ELISA kits. A total of 530 serum samples were tested for the antibodies against porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (M. hyo) and Actinobacillus pleuropneumoniae (APP). Seroprevalence for four respiratory pathogens were estimated by ELISA-positive rates of the submitted samples. The overall seropositive rates of PRRSV, APP, M. hyo and PCV2 were 32.6%, 10.6%, 38.4% and 88.5%, respectively. By production stage, the seropositive rate for PRRSV was highest in nursery pig populations (46.2%). In contrast, the highest seropositive rates of APP and M. hyo were observed in sow and growing pigs. However, the seroprevalence of PCV2 was ranged from 85.7% to 89.6%, showing no significant difference among the production stages. In the seroprevalence by season, PRRSV, APP and M. hyo infections revealed typical seasonal patterns that the peaks of the seropositive rates were observed between early winter and late spring. In case of PCV2, no particular seasonal patterns were noticed. The pig herds in Gyeongbuk province where PMWS was endemic during the period of survey showed the highest seropositive rates for PRRSV (44.6%), M. hyo (47.5%), and PCV2 (92.7%). Seropositive rates for APP of four provinces were approximately 10%. These results might be valuable for control and prevention of the respiratory diseases and helpful to define strategies related to vaccine applications.

• Journal of Veterinary Science
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• 제21권5호
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• pp.79.1-79.12
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• 2020

Background: Recently, the pork industry of Thailand faced an epidemic of highly virulent strains of porcine reproductive and respiratory syndrome virus (PRRSV), which spread throughout Southeast Asia, including the Lao People's Democratic Republic and Cambodia. Hence, the rapid and on-site screening of infected pigs on a farm is essential. Objectives: To develop the new aptamer as a biosensor for detection PRRSV which are rapid and on-site screening of infected pig. Methods: New aptamers against PRSSV were identified using the combined techniques of capillary electrophoresis, colorimetric assay by gold nanoparticles, and quartz crystal microbalance (QCM). Results: Thirty-six candidate aptamers of the PRRSV were identified from the systematic evolution of ligands by exponential enrichment (SELEX) by capillary electrophoresis. Only 8 out of 36 aptamers could bind to the PRSSV, as shown in a colorimetric assay. Of the 8 aptamers tested, only the 1F aptamer could bind specifically to the PRSSV when presented with the classical swine fever virus and a pseudo rabies virus. The QCM was used to confirm the specificity and sensitivity of the 1F aptamer with a detection limit of 1.87 × 10¹⁰ particles. Conclusions: SELEX screening of the aptamer equipped with capillary electrophoresis potentially revealed promising candidates for detecting the PRRSV. The 1F aptamer exhibited the highest specificity and selectivity against the PRRSV. These findings suggest that 1F is a promising aptamer for further developing a novel PRRSV rapid detection kit.

• Journal of Veterinary Science
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• 제22권3호
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• pp.39.18-39.18
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• 2021

Background: Interferon lambda receptor 1 (IFNLR1) is a type II cytokine receptor that clings to interleukins IL-28A, IL29B, and IL-29 referred to as type III IFNs (IFN-λs). IFN-λs act through the JAK-STAT signaling pathway to exert antiviral effects related to preventing and curing an infection. Although the immune function of IFN-λs in virus invasion has been described, the molecular mechanism of IFNLR1 in that process is unclear. Objectives: The purpose of this study was to elucidate the role of IFNLR1 in the pathogenesis and treatment of porcine reproductive and respiratory syndrome virus (PRRSV). Methods: The effects of IFNLR1 on the proliferation of porcine alveolar macrophages (PAMs) during PRRSV infection were investigated using interference and overexpression methods. Results: In this study, the expressions of the IFNLR1 gene in the liver, large intestine, small intestine, kidney, and lung tissues of Dapulian pigs were significantly higher than those in Landrace pigs. It was determined that porcine IFNLR1 overexpression suppresses PRRSV replication. The qRT-PCR results revealed that overexpression of IFNLR1 upregulated antiviral and IFN-stimulated genes. IFNLR1 overexpression inhibits the proliferation of PAMs and upregulation of p-STAT1. By contrast, knockdown of IFNLR1 expression promotes PAMs proliferation. The G0/G1 phase proportion in IFNLR1-overexpressing cells increased, and the opposite change was observed in IFNLR1-underexpressing cells. After inhibition of the JAK/STAT signaling pathway, the G2/M phase proportion in the IFNLR1-overexpressing cells showed a significant increasing trend. In conclusion, overexpression of IFNLR1 induces activation of the JAK/STAT pathway, thereby inhibiting the proliferation of PAMs infected with PRRSV. Conclusion: Expression of the IFNLR1 gene has an important regulatory role in PRRSV-infected PAMs, indicating it has potential as a molecular target in developing a new strategy for the treatment of PRRSV.