• Journal of Veterinary Science
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• v.23 no.4
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• pp.57.1-57.9
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• 2022

Background: Classical swine fever virus (CSFV), the causative agent of classical swine fever (CFS), is a highly contagious disease that poses a serious threat to Chinese pig populations. Objectives: Many provinces of China, such as Shandong, Henan, Hebei, Heilongjiang, and Liaoning provinces, have reported epidemics of CSFV, while the references to the epidemic of CSFV in Yunnan province are rare. This study examined the epidemic characteristics of the CSFV in Yunnan province. Methods: In this study, 326 tissue samples were collected from different regions in Yunnan province from 2015 to 2021. A reverse transcription-polymerase chain reaction (RT-PCR), sequences analysis, and phylogenetic analysis were performed for the pathogenic detection and analysis of these 326 clinical specimens. Results: Approximately 3.37% (11/326) of specimens tested positive for the CSFV by RT-PCR, which is lower than that of other regions of China. Sequence analysis of the partial E2 sequences of eleven CSFV strains showed that they shared 89.0-100.0% nucleotide (nt) and 95.0-100.0% amino acid (aa) homology, respectively. Phylogenetic analysis showed that these novel isolates belonged to the subgenotypes 2.1c and 2.1d, with subgenotype 2.1c being predominant. Conclusions: The CSFV was sporadic in China's Yunnan province from 2015 to 2021. Both 2.1c and 2.1d subgenotypes were found in this region, but 2.1c was dominant.

• Korean Journal of Veterinary Service
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• v.30 no.2
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• pp.205-209
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• 2007

A protein chip based on surface plasmon resonance (SPR) imaging was developed for measuring classical swine fever virus (CSFV) antibody using a recombinant gp55 protein as an antigen. The diagnostic potential of SPR imaging for detecting antibodies to the CSFV gp55 protein was compared with that of a enzyme -linked immunosorbent assay (ELISA) using 70 pig sera. There was a strong positive correlation between the SPR imaging and ELISA (n=70, r=0.916, p<0.01). Therefore, the SPR imaging, which is a label-free and high-through put method, is expected to be a valuable tool in the serodiagnosis of CSFV.

• Korean Journal of Veterinary Service
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• v.27 no.3
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• pp.239-247
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• 2004

Classical swine fever (CSF) was confirmed in 19 herds in Jeunbuk provence (Iksan, Gimje, Wanju, Buan, and Jangsu) in Korea between March and May, 2003 and 10,263 pigs were slaughtered. Pigs contacted with CSF virus in primary outbreak farm show fever, reduced appetite, arched back and chill in company with sever respirative sign and then most infected farms also were observed to fever, reduced appetite, sudden death, and leukopenia (101 pigs). In order to detecting infectious pig with CSF virus, A total of 555 pigs were inspected in 65 herds and blood samples were collected and serological test (ELISA), antigen ELISA, and reverse transcription-polymerase chain reaction (RT-PCR) had been done. Positive rate were $74\%$ (410 pigs) in antibody ELISA, $2\%$ (11 pigs) in antigen ELISA and $33\%$ (182 pigs) in RT-PCR, respectively. As shown that the RT-PCR was useful than the ELISA for determining CSF virus in blood, meat, and other organs.

• The Journal of Korean Society of Virology
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• v.28 no.4
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• pp.303-316
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• 1998

An attenuated classical swine fever virus (CSFV), Suri strain, is a variant derived from a vaccine virus, LOM strain. This study was performed to elucidate the molecular biologcal properties of CSFV Suri strain, and to obtain the basic data for molecular epidemiological approaches for the disease. The truncated form of gp55 gene without the C-terminal transmembrane domain, in size of 1,023bp, was amplified by RT-PCR and sequenced by dye terminator cyclic sequencing method, and inserted into BamHI site of pAcGP67B baculovirus vector, establishing a cloned pAcHEG plasmid. By the nucleotide sequences determined, 341 amino acid sequences were predicted. As compared the nucleotide and amino acid sequences of gp55 of Suri with the various CSFV, Suri strain showed the high homology over 99.1% with ALD and LOM strains, but comparably the lower homology with Alfort and Brescia. In comparison of amino acid sequence in variable domain of gp55 protein, the similar tendency of homology was observed. In hydrophobicity analysis, all of four CSFV strains revealed the analogous patterns of hydrophobicity. The numbers and locations of N-glycosylation site and cysteine residues in gp55 were analyzed, those of Suri strain being coincident with ALD and LOM strains. The results suggest that gp55 in Suri strain has the high similarity to those in ALD and LOM strains in terms of the nucleotide and amino acid sequences and the functional properties of gp55 protein.

• Journal of Veterinary Science
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• v.22 no.6
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• pp.87.1-87.12
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• 2021

Background: African swine fever virus (ASFV), classical swine fever virus (CSFV), and porcine reproductive and respiratory syndrome virus (PRRSV) are still prevalent in many regions of China. Co-infections make it difficult to distinguish their clinical symptoms and pathological changes. Therefore, a rapid and specific method is needed for the differential detection of these pathogens. Objectives: The aim of this study was to develop a multiplex real-time quantitative reverse transcription polymerase chain reaction (multiplex qRT-PCR) for the simultaneous differential detection of ASFV, CSFV, and PRRSV. Methods: Three pairs of primers and TaqMan probes targeting the ASFV p72 gene, CSFV 5' untranslated region, and PRRSV ORF7 gene were designed. After optimizing the reaction conditions, including the annealing temperature, primer concentration, and probe concentration, multiplex qRT-PCR for simultaneous and differential detection of ASFV, CSFV, and PRRSV was developed. Subsequently, 1,143 clinical samples were detected to verify the practicality of the assay. Results: The multiplex qRT-PCR assay could specifically and simultaneously detect the ASFV, CSFV, and PRRSV with a detection limit of 1.78 × 10⁰ copies for the ASFV, CSFV, and PRRSV, but could not amplify the other major porcine viruses, such as pseudorabies virus, porcine circovirus type 1 (PCV1), PCV2, PCV3, foot-and-mouth disease virus, porcine parvovirus, atypical porcine pestivirus, and Senecavirus A. The assay had good repeatability with coefficients of variation of intra- and inter-assay of less than 1.2%. Finally, the assay was used to detect 1,143 clinical samples to evaluate its practicality in the field. The positive rates of ASFV, CSFV, and PRRSV were 25.63%, 9.36%, and 17.50%, respectively. The co-infection rates of ASFV+CSFV, ASFV+PRRSV, CSFV+PRRSV, and ASFV+CSFV+PRRSV were 2.45%, 2.36%, 1.57%, and 0.17%, respectively. Conclusions: The multiplex qRT-PCR developed in this study could provide a rapid, sensitive, specific diagnostic tool for the simultaneous and differential detection of ASFV, CSFV, and PRRSV.

• Korean Journal of Veterinary Research
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• v.46 no.2
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• pp.107-117
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• 2006

This paper described the epidemiological characteristics of 2002 outbreak of classical swine fever (CSF) in Korea. A total of thirteen CSF-infected farms could be classified into two clusters according to the location and time of outbreak. Two farms located in the same county of Gangwon province and 11 farms located in several different districts of Incheon metropolitan/Gyeonggi province were identified as CSF-infected from April 16 to 30 and from October 7 to December 21 in 2002, respectively. As the result of epidemiological analysis, the two clusters of outbreaks were turned out to be independent epidemics which had different sources of virus introduction. Three farms were found to have been infected primarily; one located in Cheolwon county of Gangwon province and two located in Kangwha county of Incheon metropolitan area. The most likely factors of virus introduction into these primary infected farms were considered to be direct or indirect contact by foreign workers and/or owners of the infected farms who had come back from traveling in China before outbreaks. This was supported by the genetic typing of CSF viruses isolated from the pigs of infected farms. All the virus isolates of 2002 outbreak were found to be genetic type 2, whereas the viruses isolated before 2000 were type 3 and the reference strains, such as attenuated live vaccine virus (LOM strain) and high virulent challenge virus (ALD strain), were type 1. Accordingly, we concluded that the 2002 CSF outbreak must have been caused by a newly introduced virus from overseas and the type 3 virus must have been eradicated after the last outbreak of 1999 by the national CSF eradication campaign which were implemented since 1996. Based on the combined analysis of epidemiological data and genetic typing, the transmission routes of classical swine fever virus were found to be the movement of vehicles (60%) and persons (10%), neighbourhood spread (20%) and unknown (10%). It is expected that the analyzed data and findings of classical swine fever outbreak epidemic could be very useful to establish the disease control and eradication program for the country in the future.

• Journal of Microbiology and Biotechnology
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• v.27 no.9
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• pp.1701-1710
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• 2017

Classical swine fever virus (CSFV) is the etiologic agent of classical swine fever, a highly contagious disease that causes significant economic losses to the swine industry. The lapinized C-strain, a widely used vaccine strain against CSFV, has low growth efficiency in cell culture, which limits the productivity in the vaccine industry. In this study, a recombinant virus derived from C-strain was constructed and subjected to continuous passaging in PK-15 cells with the goal of acquiring a high progeny virus yield. A cell-adapted virus variant, RecCpp80, had nearly 1,000-fold higher titer than its parent C-strain but lost the ability to induce fever in rabbits. Sequence analysis of cell-adapted RecC variants indicated that at least six nucleotide changes were fixed in RecCpp80. Further adaption of RecCpp80 variant in swine testicle cells led to a higher virus yield without additional mutations. Introduction of each of these residues into the wild-type RecC backbone showed that one mutation, M979R (T3310G), located in the C-terminal region of E2 might be closely related to the cell-adapted phenotype. Rabbit inoculation revealed that $RecCpp40_{+10}$ failed to induce fever in rabbits, whereas $RecCpp80_{+10}$ caused a fever response similar to the commercial C-strain vaccine. In conclusion, the C-strain can be adapted to cell culture by introducing specific mutations in its E2 protein. The mutations in RecCpp80 that led to the loss of fever response in rabbits require further investigation. Continuous passaging of the C-strain-based recombinant viruses in PK-15 cells could enhance its in vitro adaption. The non-synonymous mutations at 3310 and 3531 might play major roles in the enhanced capacity of general virus reproduction. Such findings may help design a modified C-strain for improved productivity of commercial vaccines at reduced production cost.

• Korean Journal of Veterinary Research
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• v.52 no.4
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• pp.259-262
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• 2012

Classical swine fever (CSF) is a highly contagious disease among swine that has an important economic impact on worldwide. One clinical symptom of CSF is leukopenia, in particular lymphopenia, which is a characteristic event that occurs early in the course of CSF. Though lymphopenia associated with apoptosis, the pathogenic mechanism underlying the lymphopenia has not been well studied. To understand these mechanisms, we investigated the response of porcine B cell lines to infection with SW03, virulent strain isolated from swine tissue in Korea. This study demonstrated that SW03-infected L35 cell were induced apoptosis through the detection of activated caspase-3. In addition, SW03 infection leaded to alterations in pro-apoptotic, Bax, and anti-apoptotic, Bcl-xL proteins of Bcl-2 family. Our results would suggest that SW03-infected L35 cells induced apoptosis via intrinsic mitochondrial pathway.

• Korean Journal of Veterinary Research
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• v.43 no.2
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• pp.263-270
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• 2003

The objective of the present study was to investigate the use of fluid released from muscle samples as an alternative to serum for ELISA to detect classical swine fever(CSF) virus antibodies in slaughter pigs. The optimal correspondence between serum 1:20 OD values and muscle fluid OD values was achieved at a muscle fluid dilution of 1:2. Significant correlation was found between serum and neck muscle ELISA ($r_s=0.880$, p<0.0001, ${\kappa}=0.82$; specificity of 97.0% and sensitivity 90.6%). The semimembranous muscle showed similar correlation in CSF ELISA($r_s=0.877$, p<0.0001, ${\kappa}=0.75$; specificity of 94.1% and sensitivity 89.1%). High correlation was obtained between serum and mesenteric lymph node in the CSF ELISA ($r_s=0.937$, p<0.0001, ${\kappa}=0.87$; specificity of 97.1% and sensitivity 93.0%). Measmement agreement between serum ELISA and muscle fluid ELISA was calculated and expressed as limits of agreement. The correspondence of ELISA of serum and muscle fluid indicated limits of agreement. Above 95% of all muscle fluid values were distributed within this limits of agreement. Among the samples used for ELISA for detecting CSFV antibodies, mesenteric lymph node had the most correlation and agreement with serum ELISA. F-test for comparison of variances showed no significant difference between the serum and muscle fluid. In conclusion, muscle fluid is a useful postmortem alternative to serum to detect CSFV antibodies.

• Korean Journal of Veterinary Service
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• v.26 no.1
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• pp.1-9
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• 2003

The aim of this survey was to investigate the characteristics of outbreak farm determined as the classical swine fever(CSF) at Gangwha-gun and Seo-gu, Incheon metropolitan area from October 7 to November 25 in 2002. Sixty pigs in six different farms were confirmed to the CSF and a total of 9,106 pigs containing 3,194 related epidemiologically was slaughtered to stop spreading of the disease. Clinical signs of pigs diagnosed with the CSF were high fever, anorexia, depression, paralysis of hindlimbs, cyanosis, etc and gross lesions were typically represented with hemorrhage of submandibular and superficial lymph node, infarction of spleen, and petechial (ecchymotic) hemorrhage of kidney and skin. But some outbreak farms had not shown remarkable symptoms, so they were confused with other bacterial diseases. White blood cell (WBC) counts, the classical swine fever virus(CSFV) antigen and antibody enzyme linked immunosorbent assay(ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR) results about six farms indicated that total 60 pigs were infected with the CSFV. Although the origin and infection route of the CSFV were not clear, but the transmissions between farms were mainly through indirect contact such as the movement of farm personal and vehicles from outbreak farm.