• Korean Journal of Veterinary Research
• /
• v.46 no.4
• /
• pp.363-370
• /
• 2006

Porcine reproductive and respiratory syndrome (PRRS) is an economically important disease of swine that occurs all over the swine industry worldwide. It was first observed in the Unite States in 1987 then in Europe in 1990. It has been described in Japan and in Korea in 1993. PRRS virus is divided into two distinct types, North American and European, genetically. Based on our limited knowledge there has been no report on the existence of European PRRSV. But according to the government's Korea Customs Service there has been many importations of breeding pigs from Europe. These seem to make an estimate that European PRRSV could be introduced in Korea by inflow of European breeding pigs. We first detected the European PRRSV could be introduced in Korean pig farms by using polymerase chain reaction (PCR). Further, it is also identified that there are not only North American PRRSV antibody but also a European PRRSV antibody. According to the genetical and serological experiment results, the presence of established North American PRRSV in Korea is due to the use of live vaccines made of North American PRRSV strain as well field virus infection, and the European PRRSV is possibly introduced from imported breeding stock.

• Korean Journal of Veterinary Service
• /
• v.37 no.1
• /
• pp.1-9
• /
• 2014

Although it has been generally accepted that porcine reproductive and respiratory syndrome virus (PRRSV) induces weak and delayed protective immunity after infection, it is unclear that the same immunological features can be applicable to all PRRS viruses because huge genetic variation exists even among the same genotypes of PRRSV (Type 1 and 2). In the current study, two genetically distinct type 2 PRRSV strains (VR-2332 and JA142) which showed approximately 90% nucleotide homology based on ORF5 sequences were characterized by both in vitro and in vivo assessments to determine the immunological features of the viruses. For in vitro assessment, porcine alveolar macrophages (PAM) were infected with the viruses at $10^{-3}$ multiplicity of infection (MOI) and then supernatants and cells were collected separately at 36 hrs post infection to determine the relative expression levels of IL-$1{\alpha}$, IL-12, TNF-${\alpha}$ and INF-${\alpha}/{\beta}$ by quantitative RT-PCR. In addition, five PRRSV-free pigs were inoculated with either of JA142 or VR2332 for in vivo assessment. Serum samples were collected every week until 6 weeks post challenge. The serum samples were analyzed for the levels of viremia, PRRSV nucleocapsid-specific antibody and virus neutralizing antibody. Based on those assessments, the two viruses showed different patterns of cytokine expression in PAM and immune responses in pigs after infection. These results indicate that genetically distinct PRRSV strains have different immunological features, which might be criteria for virus classification and selection of candidate virus strains for vaccine development in the future.

• Korean Journal of Veterinary Research
• /
• v.39 no.1
• /
• pp.133-137
• /
• 1999

The 2,078 blood samples from 148 swine farms were collected and tested by IFA for porcine reproductive and respiratory syndrome(PRRS) virus antibody to know what type of PRRS prevails by the area. Clinically reproductive form of PRRS occurred in swine farms of 3/27, 3/87, and 2/34 in eastern, central and western areas, but the seroprevalence of those areas was different as 6.5%, 23.3%, and 17.6%, respectively. However, respiratory form of PRRS occurred more frequently, and the number of farms manifested with the respiratory form of PRRS in the eastern, central and western areas was 22/27, 71/87, and 30/34, respectively. The seroprevalence of that form of PRRS in the eastern, central and western areas was 52.2%, 67.1%, and 51.6%, respectively. Subsequently mixed form of PRRS occurred more frequently in the central area and the number of farms of eastern, central and western areas was 2/27, 13/87, and 2/34, respectively. The PRRS seroprevalence of the eastern, central and western areas was 58.6%, 54.0%, and 19.2%, respectively. Collectively the PRRS seroprevalence of eastern, central and western areas was 43.8%, 59.3%, and 38.2%, respectively. Overall seroprevalence of PRRS in Korea was 51.8%. In conclusion, the reproductive or the respiratory form of PRRS has been still in trouble in the Korean swine industry and PRRS control measures have to be taken in consideration.

• Journal of Veterinary Clinics
• /
• v.33 no.2
• /
• pp.102-106
• /
• 2016

More than 20 years after the first report of porcine reproductive and respiratory syndrome virus (PRRSV) in Korea, the disease is still having major impact on domestic pig health and relevant industries. Although ELISA tests are commonly used by veterinarians to guide herd management, data on diagnostic performance of the test in field settings are very limited. The objective of this study was to evaluate two commercially available PRRSV ELISA (IDEXX PRRS X3 ELISA and Bionote PRRSV ELISA 4.0) to detect antibodies against PRRSV on serum samples. To this end, a total of 1,108 sera were recruited from 35 swine farms located in Gyeonggi province and tested at the Gyeonggi Province Veterinary Service Center. All tests were performed according to the manufacturer's instructions, by laboratory technicians who routinely perform PRRS testing on blood samples. Samples were collected from two sources of swine populations with different PRRS prevalence; 60 samples (5.4%) were originated from breeding farms and the remaining 1,048 samples (94.6%) were from farrow-to-finish farms. We applied Bayesian latent class model (LCM) for two-tests in the two-population when the accuracy of the gold standard is not available. The model estimated that Bionote ELISA was a bit more specific but slightly less sensitive. The estimated sensitivity and specificity of the IDEXX ELISA were 99.8% (95% CI 98.1-100%) and 86.4% (95% CI 81.4-96.5%), respectively. Sensitivity, specificity, positive predictive value and negative predictive value for Bionote kit were 98.7% (95% CI 92.8-100%), 89.8% (95% CI 86.2-93.1%), 93.8% (95% CI 91.5-96.0%), and 97.8% (95% CI 87.1-100%), respectively. Based on the Bayesian 95% credible intervals, the sensitivity and specificity of the two ELISAs were not significantly different each other when assuming that two kits were imperfect, indicating that two kits performed equally well in terms of sensitivity and specificity in our filed setting.

• Korean Journal of Veterinary Research
• /
• v.48 no.1
• /
• pp.67-73
• /
• 2008

Porcine reproductive and respiratory syndrome (PRRS) is the most economically important viral infectious disease in pig populations worldwide. This study was conducted to better understand the epidemic and dynamics of PRRS virus (PRRSV) on each farm and to evaluate the risk of PRRSV infection in Korea. Interviews with pig farmers were carried out to obtain PRRS vaccination programmes in 60 pig farms throughout Korea. Blood samples were also collected from the 59 pig farms to investigate outbreak patterns of each farm. Vaccination against PRRS was performed in 16.7% farms for breeding pigs and 8.3% of farms for nursery pigs. According to the seroepidemiological analysis, 56 (94.9%) out of 59 farms were considered to be affected by PRRSV infection. The results revealed that 68.9% of sows tested were seroconverted and interestingly, gilt herds had the highest seropositive rate (73%), suggesting that gilts may play a key role in PRRSV transmission in sow herds. Among the PRRS-affected piglet herds, 33 (55.9%), 14 (23.7%) and 6 (10.2%) farms were initially infected with PRRSV during the weaning, suckling and nursery period, respectively. It seems likely, therefore, that PRRSV infection predominantly occurs around the weaning period in piglet herds. Based on antibody seroprevalence levels in both sow and piglet groups, we were able to classify patterns of PRRSV infection per farm unit into 4 categories; category 1 (stable sow groups and non-infected piglet groups), category 2 (unstable sow groups and non-infected piglet groups), category 3 (stable sow groups and infected piglet groups), and category 4 (unstable sow groups and infected piglet groups). Our data suggested that 43 (72.9%) farms were analysed to belong to category 4, which is considered to be at high-risk for PRRS outbreak. Taken together, our information from this study will provide insight into the establishment of an effective control strategy for PRRS on the field.

• Korean Journal of Veterinary Service
• /
• v.37 no.1
• /
• pp.11-18
• /
• 2014

Porcine reproductive and respiratory syndrome (PRRS) causes a significant economic loss in the swine industry not only in Korea but also all over the world. Andong and Hapcheon region were selected for Area Regional Control (ARC) programme to reduce the shedding of PRRS virus (PRRSV) and decrease PRRS outbreaks. Before conducting the PRRS ARC, sera of pigs were tested for both antibody using ELISA and antigen using RT-PCR, then phylogenetic classifications was analysed. Pigs of 138/275 (50.2%) in Andong and 352/425 (82.8%) in Hapcheon were seropositive. Also, the RT-PCR results revealed that 27 heads (8.2%) in Andong, 112 heads (22.0%) in Hapcheon were positive for PRRSV antigen. PRRSVs were mainly detected between the ages of 40 to 60 days. PRRSV ORF5 regions were used to determine genetic clusters based on previous report. All PRRSV type I detected in both Andong and Hapcheon were classified as Cluster I. The PRRSV type II isolates in Andong were assorted to Cluster II, whereas the PRRSV type II isolates in Hapcheon were the viruses were unassembled into any cluster except one identified to Cluster III. Phylogenetic analysis indicated that new clusters of PRRSVs type II were prevalent in Hapcheon.

• Korean Journal of Veterinary Service
• /
• v.24 no.4
• /
• pp.359-367
• /
• 2001

A serological survey was performed to establish basic data for the prevalence of antibodies to some major diseases of domesticated boar serum samples from January to December 2000. Sera collected in breeding farms in Gyeongbuk province were tested for Aujeszky's disease virus(ADV), Porcine reproductive and respiratory syndrome virus(PRRSV), Porcine parvovirus(PPV), Japanese encephalitis virus (JEV), Bordetella bronchiseptica(B bronchiseptica), Mycoplasma ; APP), Toxoplasma, and Brucella. There was no antibody to ADV in domesticated boars serum samples detected by Anti-ADV-gpI assay kit. Sero-positive samples to PRRS by IFA were 0.9%(3/330) The HI titers to PPV ranged variously from less than 10 to over 1,280. Two hundred ninety-four out of 330 tested sera showed HI titer of less than 10. In HI test to JEV, 90.3% of the sera (298/330) were below 10. The majority of the serum samples had low prevalence of the antibody B bronchiseptica. ELISA titers to M hyopneumoniae ranged variously from $\leq$ 10 to $\geq$ 1,280. Antibody titers to A pleuropneumoniae type 2(APP2) and type 5(APP5) were 58.2% and 52.7%, respectively, and the tested samples showing ELISA antibody titers of less than 20. There was no significant geographical difference between APP2 and APP5 in this study. In the antibody test of Toxoplasma, 11.5%(38/330) were positive and samples were all negative in sera test of Brucella.

• Korean Journal of Veterinary Service
• /
• v.37 no.3
• /
• pp.143-150
• /
• 2014

Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiological agent of PRRS characterized by reproductive losses in sows and respiratory disorders in piglets. The PRRSV is a small enveloped virus containing a positive-sense, single-stranded RNA genome and divided into two genotype, type 1 (European) and type 2 (North American), respectively, by nucleotide identity. In this study, ORF7 gene of the type 1 and type 2 PRRSV was cloned and expressed in Baculovirus expression system. Also, monoclonal antibodies (MAbs) against ORF7 were produced and characterized. The expressed ORF7 proteins in the recombinant virus were confirmed by indirect fluorescence antibody (IFA) test using His6 and PRRSV-specific antiserum. A total of eight MAbs were produced and characterized. One (3G12) MAb was type 1 PRRSV ORF7-specific and two (6B10 and 16H8) were type 2 PRRSV ORF7-specific. Other five (1A1, 2A4, 4B4, 12C4 and 13F11) MAbs reacted with both type 1 and type 2 PRRSV. Some PRRSV ORF7-specific MAbs recognized the porcine tissues infected with PRRSV by IFA or immunohistochemistry (IHC) assay. From this experiment, it was confirmed that MAbs produced in this study were PRRSV ORF7-specific and could be used as reliable reagents for type 1/type 2 PRRSV detection.

• Korean Journal of Veterinary Research
• /
• v.43 no.3
• /
• pp.463-469
• /
• 2003

Eight nursery to grower pigs exhibiting weight loss and sudden death were diagnosed as postweaning multisystemic wasting syndrome (PMWS) based on the results of gross findings, histopathology, immunohistochemistry, fluorescent antibody test, virus isolation, PCR, serology, and electron microscopy. Groosly, the pigs had a rough hair coats and were severely emaciated. And moot lymph nodes were pale and enlarged. Lungs were not fully collapsed and exhibited 10 to 40% pale red cranioventral consolidation. Histopathologically, typical lymphohistiocytic interstitial to bronchointerstitial pneumonia, chronic lymphadenitis, severe lymphoid depletion, and basophilic intracytoplasmic inclusions were noted in the most lymphoid tissues. Porcine circovirus panicles were observed in the inguinal lymph node of the pigs by electron microscopy. Porcine circovirus type 2 (PCV2) antigens or viral DNAs were detected in the lesions of all pigs using immunohistochemistry or PCR. Two PCV2 were isolated from a homogenate of pooled lung and lymph node in 2 of the 5 pigs. Additionally, antigens of porcine reproductive and respiratory syndrome virus (PRRSV) and Hemophilus (H.) parasuis were also detected by immunofluorescent antibody test. Serologically, 55% of randomly selected sows and fattening pigs was serum antibody positive to PCV2 by an indirect fluorescent antibody (IFA) test and approximately 18 % of animals in the herd were serologically pooitive by the ELISA kit for PRRSV. To our knowledge, this is the first report of PMWS co-infected with PCV-2, PRRS, and H. parasuis in Korea.

• Korean Journal of Veterinary Research
• /
• v.58 no.2
• /
• pp.73-79
• /
• 2018

Outbreaks of porcine reproductive and respiratory syndrome virus (PRRSV) in vaccinated sow herds from occurrence to stabilization were monitored and analyzed in terms of serology and reproductive performance. Three different conventional pig farms experienced severe reproductive failures with the introduction of a type 1 PRRSV. These farms had adopted mass vaccination of sows using a type 2 PRRSV modified live vaccine (MLV). Therefore, to control the type 1 PRRSV, an alternative vaccination program utilizing both type 1 and type 2 MLV was undertaken. Following whole herd vaccinations with both types of MLV, successful stabilization of PRRS outbreaks was identified based on serological data (no viremia and downward trends in ELISA antibody titers in both sows and suckling piglets) and recovery of reproductive performance. Additionally, through comparison of the reproductive parameters between outbreak and non-outbreak periods, it was identified that PRRSV significantly affected the farrowing rate and the number of suckling piglets per litter at all three pig farms. Comparison of reproductive parameters between periods when the different vaccination strategies were applied revealed that the number of piglets born in total and born dead per litter were significantly increased after the introduction of the type 1 PRRS MLV.