Prevalence of Classical Swine Fever Virus in Domestic Pigs in South Korea: 1999-2011

Song, Jae‐Young; Lim, Suk-Kyung; Jeoung, Hye-Young; Choi, Eui Yul; Hyun, Bang-Hun; Kim, B.; Kim, J.; Shin, Yeun Kyung; Pena, R. C. dela; Kim, J. B.; Joo, H.S.; An, Dong-Jun

doi:10.1111/j.1865-1682.2012.01371.x

Cited by 19 publications

(18 citation statements)

References 9 publications

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“…A mandatory vaccination policy, using the LOM strain of CSFV, has been implemented in the mainland of South Korea since 2003. Based on the high levels of seropositivity, it has been recognized that herd immunity against CSFV was established in domestic swine herds (Song et al., ). However, sporadic CSF outbreaks have occurred continuously.…”

Section: Discussionmentioning

confidence: 99%

Genetic evolution of classical swine fever virus under immune environments conditioned by genotype 1-based modified live virus vaccine

Yoo

Kwon

Kang³

et al. 2018

Transbound Emerg Dis

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Modified live vaccines (MLVs) based on genotype 1 strains, particularly C-strain, have been used to prevent and control classical swine fever virus (CSFV) worldwide. Nevertheless, a shift in the predominant CSFV strains circulating in the field from genotype 1 or 3 to genotype 2 is seen. Genotype 2 is genetically distant from the vaccine strains and was recently reported during outbreaks after vaccine failure; this has raised concerns that vaccination has influenced viral evolution. In Korea in 2016, there was an unexpected CSF outbreak in a MLV-vaccinated commercial pig herd. The causative CSFV strain was genetically distinct from previously isolated Korean strains but similar to recent Chinese strains exhibiting enhanced capacity to escape neutralization; this suggests the need for global cooperative research on the evolution of CSFV. We analysed global E2 sequences, using bioinformatics tools, revealing the evolutionary pathways of CSFV. Classical swine fever virus genotypes 1 and 2 experienced different degrees and patterns of evolutionary growth. Whereas genotype 1 stayed relatively conserved over time, the genetic diversity of genotype 2 has progressively expanded, with few fluctuations. It was determined that genotype 2 evolved under lower immune pressures and at a higher evolutionary rate than genotype 1. Further, several selected codons, under diversifying selection in genotype 1 but under purifying selection in genotype 2, correspond to antigenic determinants, which could lead to evasion of vaccine-induced immunity. Our findings provide evidence that evolutionary changes in CSFV are the result of the disproportionate usage of the CSF MLVs in endemic areas; this underscores the need to develop mitigation strategies to minimize the substantial risk associated with the emergence of vaccine-escaping mutants.

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Section: Discussionmentioning

confidence: 99%

Genetic evolution of classical swine fever virus under immune environments conditioned by genotype 1-based modified live virus vaccine

Yoo

Kwon

Kang³

et al. 2018

Transbound Emerg Dis

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“…CSF has been controlled and eradicated from most of the countries using vaccination campaigns (Van Oirschot ; Greiser‐Wilke & Moennig ; Song et al . ; Luo et al . ).…”

Section: Introductionmentioning

confidence: 99%

“…CSF has been controlled and eradicated from most of the countries using vaccination campaigns (Van Oirschot 2003;Greiser-Wilke & Moennig 2004;Song et al 2013;Luo et al 2014). However, CSF remains a threat to pigs raised in South Asia, including India, Nepal and Bhutan (Gatenby & Chemjong 1992;Dukpa et al 2011;Prasad et al 2011).…”

Section: Introductionmentioning

confidence: 99%

An outbreak of classical swine fever in pigs in Bangladesh, 2015

Sarkar

Hossain

Gurley

et al. 2017

Veterinary Medicine & Sci

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In a group of 22 healthy pigs aged between 4 and 6 months, 2 pigs became ill with high fever, complete anorexia, cough and abnormal swaying movements on 22 June 2015. One of them died on June 24 and the second died on July 3. Shortly after, the remaining pigs also fell ill and died from the same illness by 10 August 2015. We investigated the aetiology, epidemiological and clinical features of the outbreak. We recorded the clinical signs and symptoms for each pig with the date of onset of illness. Veterinarians conducted post‐mortem examinations on the 12 dead pigs, they collected tissue samples from the dead pigs and placed them in a tube containing 1 mL of nucleic acid extraction buffer (lysis buffer). We tested all the tissue samples by real‐time reverse transcription polymerase chain reaction (rRT‐PCR) to detect classical swine fever virus (CSFV) because the animals’ symptoms matched those of this disease. We also conducted a phylogentic analysis of the nucleotide sequence of the E2 gene segment of CSFV detected in a lung tissue sample. The attack rate (22/22) and the case fatality were 100%. The predominant symptoms of the disease included high fever, cough, diarrhoea and swaying movements of the hind legs prior to death. Of the 12 pigs tissue samples tested, all had evidence of the presence of CSFV RNA by rRT‐PCR. The phylogenetic analysis indicated that the virus belongs to genotype 2.2, which is closely related to CSFV genotype 2.2 reported in India. Our investigation suggests that CSF is circulating in pigs, posing a risk for communities in Bangladesh that rely on pigs for economic income and dietary protein. Future research could focus on estimating the disease and economic burden of CSFV in pig rearing areas to determine if interventions might be warranted or cost‐effective.

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“…In contrast, the national government‐driven CSF eradication program has succeeded in Jeju Province, the largest island in South Korea that is 80 and 304‐km away from the mainland at the closest and farthest points respectively. Consequently, Jeju Island banned vaccination in 1998 and became a CSF‐free region in 1999, and since then, had maintained a CSFV‐naïve status for over a decade (Song et al., ). However, CSFV simultaneously re‐emerged on Jeju Island in 2014 in areas with extensive pig production.…”

Section: Introductionmentioning

confidence: 99%

Endemic outbreaks due to the re‐emergence of classical swine fever after accidental introduction of modified live LOM vaccine on Jeju Island, South Korea

Jang

Kim²,

Kang³

et al. 2019

Transbound Emerg Dis

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Summary After the unintentional vaccination of the LOM vaccine strain in 2014, classical swine fever virus (CSFV) reemerged in naïve pig herds on Jeju Island, South Korea, which had been a CSF‐free region with a non‐vaccination policy for a decade. Since the re‐emergence, endemic outbreaks of CSFV have occurred in the island, causing enormous damage to provincial pig farms. The present study reports the complete genome sequences and molecular characterization of the LOM‐derived field CSFV strains responsible for the current outbreaks on Jeju Island. The emergent Jeju LOM‐derived isolates shared 98.9%–99.7% and 98.7%–99.0% nucleotide sequence identity at the E‐gene and whole‐genome levels compared to the LOM vaccine strain respectively. Genetic and phylogenetic analyses indicated that the CSFV field isolates were closest to the LOM strains, but appeared to have undergone substantial evolution. The total number of nucleotide and amino acid differences between the LOM vaccine strain and LOM‐derived field isolates ranged from 111 and 28 to 148 and 42. These variations were found to be widely distributed throughout the genome and particularly accumulated in non‐structural proteins, which might be associated with the potential for LOM to revert to its original low pathogenic form and subsequent horizontal transmission in Jeju swine herds. These data improve our knowledge regarding safety of the LOM vaccine and inherent risk of reversion to natural virulence in host animals.

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Prevalence of Classical Swine Fever Virus in Domestic Pigs in South Korea: 1999-2011

Cited by 19 publications

References 9 publications

Genetic evolution of classical swine fever virus under immune environments conditioned by genotype 1-based modified live virus vaccine

Genetic evolution of classical swine fever virus under immune environments conditioned by genotype 1-based modified live virus vaccine

An outbreak of classical swine fever in pigs in Bangladesh, 2015

Endemic outbreaks due to the re‐emergence of classical swine fever after accidental introduction of modified live LOM vaccine on Jeju Island, South Korea

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