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Detection of viral RNA and virus shedding in Classical swine fever virus-infected pigs by reverse transcriptase-polymerase chain reaction
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Classical swine fever (CSF), a highly contagious disease that affects domestic pigs and wild boar, has serious economic implications. The present study examined the virulence and transmission of CSF virus strain YC11WB (isolated from a wild boar in 2011) in breeding wild boar. Virulence of strain YC11WB in domestic pigs was also examined. Based on...
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... was performed to detect viremia and viral shedding in pigs after challenge with strains YC11WB or SW03. Virus were detected in blood samples from two breeding wild boar (W26 and W28) at 3 DPI, and another two (NW35 and NW32 Journal of Veterinary Science in Group 2) wild boar at 3 and 5 DPI, respectively ( Table 2). Analysis of blood, nasal, fecal, and salivary fluid samples from animals in Group 3 revealed that all pigs were positive at 5 DPI (Table 2). ...
Context 2
... were detected in blood samples from two breeding wild boar (W26 and W28) at 3 DPI, and another two (NW35 and NW32 Journal of Veterinary Science in Group 2) wild boar at 3 and 5 DPI, respectively ( Table 2). Analysis of blood, nasal, fecal, and salivary fluid samples from animals in Group 3 revealed that all pigs were positive at 5 DPI (Table 2). At 5 DPI, blood samples from pigs in Group 4 showed evidence of viremia and fecal samples showed evidence of viral shedding. ...
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Classical swine fever (CSF) is an important viral disease of domestic pigs and wild boar. The structural proteins E2 and Erns of classical swine fever virus (CSFV), which participate in the attachment of the virion to the host cell surface and its subsequent entry, are immunogenic. The E2 and Erns proteins are used for diagnosis and the development...
Classical swine fever (CSF) is a systemic hemorrhagic disease affecting domestic pigs and wild boars. The modified live vaccine (MLV) induces quick and solid protection against CSF virus (CSFV) infection. Maternally derived antibodies (MDAs) via colostrum could interfere with the MLV’s efficacy, leading to incomplete protection against CSFV infecti...
Classical swine fever virus (CSFV) causes one of the most critical diseases in the porcine industry worldwide. In Brazil, the first description of the infection was reported in 1888, and the national recognition of the first free zone (FZ) occurred in 2001. Brazil has been recently recognized (2015–2016) by the World Organisation for Animal Health...
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... Interestingly, the YC16CS strain in 2016 was the first suspected case of infection between wild boars and domestic pigs (because GG province is where CSF was detected in wild boars in 2011) [4]. The wild boar YC11WB strain (CSFV subgenotype 2.1d) isolated in 2011 is highly pathogenic in domestic pigs [34]. However, the recently isolated CSFV subgenotype 2.1d from Japan showed moderate pathogenicity [32,33]. ...
Classical swine fever virus (CSFV) is one of the major pathogens that causes severe economic damage to the swine industry. Circulation of CSFV in wild boars carries the potential risk of reintroducing the virus into CSFV-free pig farms. This study carried out a genetic analysis of CSFV isolates from wild boars and analyzed the mtDNA haplotypes of the wild boars. Blood samples (n = 2140) from wild Korean boars captured in 2020 were subjected to qRT-PCR to detect CSFV, which was classified as subgenotype 2.1d based on phylogenetic analysis. CSFV had been detected in wild boars only in northern regions (Gangwon and Gyeonggi) of South Korea between 2011 and 2019. However, CSFV was identified in wild boars in the more southern regions (Chungbuk and Gyeongbuk) in 2020. Based on mitochondrial DNA analysis, all wild boars with CSFV were haplotype 01 (H01). Thus, we presume that the H01 haplotype is more susceptible to CSFV. In the future, infection of wild boars by CSFV is expected to occur intermittently every year, and we predict that most wild boars infected with CSFV will be haplotype H01.
... Despite the mandatory vaccination policy ruled for several years, sporadic CSF outbreaks have occurred in mainland South Korea [42][43][44] suggesting either an evolutionary process of circulating strains toward an escaping lineage of CSFV or a potential reversion to virulence by the vaccine strain. In addition, it has been informed that since 2002, CSF in Korea has undergone an antigenic shift from genotype 3 to genotype 2 [226]. In 2014, CSF reemerged in naïve pig herds on Jeju Island, South Korea, caused by the reversion to the virulence by the LOM vaccine strain [46]. ...
Classical swine fever (CSF) is, without any doubt, one of the most devasting viral infectious diseases affecting the members of Suidae family, which causes a severe impact on the global economy. The reemergence of CSF virus (CSFV) in several countries in America, Asia, and sporadic outbreaks in Europe, sheds light about the serious concern that a potential global reemergence of this disease represents. The negative aspects related with the application of mass stamping out policies , including elevated costs and ethical issues, point out vaccination as the main control measure against future outbreaks. Hence, it is imperative for the scientific community to continue with the active investigations for more effective vaccines against CSFV. The current review pursues to gather all the available information about the vaccines in use or under developing stages against CSFV. From the perspective concerning the evolutionary viral process, this review also discusses the current problematic in CSF-endemic countries.
... The NA5 strain showed high sequence similarity with seven Korean CSFV strains (KSB06N01, YJB08B2, LSG03N46, SW03N8, CW02N13, MBG07N01, and KH2002N1): 96.7%-99.5% at the nucleotide level and 97.3%-99.5% at the amino acid level. The Korean sub-genotype 2.1b strains showed moderate pathogenicity when inoculated into pigs and did not show high pathogenicity, even in field CSF outbreaks [16,17]. One of two landrace pigs infected with strain SW03 (10 6.0 TCID50/ml) died at 18 dpi, but one lived until 21 dpi [17]. ...
... The Korean sub-genotype 2.1b strains showed moderate pathogenicity when inoculated into pigs and did not show high pathogenicity, even in field CSF outbreaks [16,17]. One of two landrace pigs infected with strain SW03 (10 6.0 TCID50/ml) died at 18 dpi, but one lived until 21 dpi [17]. The viral RNA copy number in organs/tissues from the two pigs infected with the SW03N8 strain was somewhat lower (10 1.08-4.82 ...
... The viral RNA copy number in organs/tissues from the two pigs infected with the SW03N8 strain was somewhat lower (10 1.08-4.82 log10) in tonsil, lung, heart, mesenteric lymph node, and cecum than that with the YC11WB strain [17]. Therefore, we think that based on its genetic similarity with the Korean CSFV sub-genotype 2.1b, the Vietnamese NA5 strain has moderate virulence. ...
Here, we examined the pathogenicity and genetic differences between classical swine fever viruses (CSFV) isolated on pig farms in North Vietnam from 2014–2018. Twenty CSFV strains from 16 pig farms were classified as genotype 2 (sub-genotypes 2.1b, 2.1c, and 2.2). The main sub-genotype, 2.1c, was classified phylogenetically as belonging to the same cluster as viruses isolated from the Guangdong region in South China. Strain HY58 (sub-genotype 2.1c), isolated from pigs in Vietnam, caused higher mortality (60%) than the Vietnamese ND20 strain (sub-genotype 2.2). The Vietnamese strain of sub-genotype 2.1b was estimated to have moderate virulence; indeed, genetic analysis revealed that it belongs to the same cluster as Korean CSFV sub-genotype 2.1b. Most CSFVs circulating in North Vietnam belong to sub-genotype 2.1c. Geographical proximity means that this genotype might continue to circulate in both North Vietnam and Southern China (Guangdong, Guangxi, and Hunan).
... The virulence of CSFV is categorized via a clinical score into highly virulent, moderately virulent, low virulent, and avirulent [6,7]. Although the CSFV genotype 2.1b isolated from the Republic of Korea was highly virulent, the same genotype isolated in Mongolia was moderately virulent [8,9]. Moreover, the recently classified CSFV genotype 2.1d from China was moderately virulent compared to different variants and antigenicity from field strains identified in China in the past [10]. ...
Since September 2018, nearly 900 notifications of classical swine fever (CSF) have been reported in Gifu Prefecture (Japan) affecting domestic pig and wild boar by the end of August 2019. To determine the epidemiological characteristics of its spread, a spatio-temporal analysis was performed using actual field data on the current epidemic. The spatial study, based on standard deviational ellipses of official CSF notifications, showed that the disease likely spread to the northeast part of the prefecture. A maximum significant spatial association estimated between CSF notifications was 23 km by the multi-distance spatial cluster analysis. A space-time permutation analysis identified two significant clusters with an approximate radius of 12 and 20 km and 124 and 98 days of duration, respectively. When the area of the identified clusters was overlaid on a map of habitat quality, approximately 82% and 75% of CSF notifications, respectively, were found in areas with potential contact between pigs and wild boar. The obtained results provide information on the current CSF epidemic, which is mainly driven by wild boar cases with sporadic outbreaks on domestic pig farms. These findings will help implement control measures in Gifu Prefecture.
... In east Asia, virulence of two field subgenotype 2.1b isolates from south Korea and Mongolia were recently evaluated. Results showed that the south Korean isolate, from a wild boar, caused death of all experimentally infected domestic pigs by 16 DPI, but pigs infected with the Mongolian isolate displayed no overt clinical signs and all survived the challenge during a 21-day observation period (Enkhbold et al., 2017;Lim et al., 2017). Most recently in China two laboratories have reported the virulence evaluation of two field CSFV isolates of subgenotype 2.1b from Heilongjiang province Zhang et al., 2018). ...
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.
