Classical Swine Fever

A special issue of Pathogens (ISSN 2076-0817).

Deadline for manuscript submissions: closed (31 August 2020) | Viewed by 58848

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School of Veterinary Medicine, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
Interests: veterinary pathology; diagnostic pathology; pathogenesis of viral diseases and of swine diseases
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Guest Editor
School of Veterinary Medicine, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
Interests: pestiviruses; virulence; pathogenesis; viral glycoprotein structure and function; epitope mapping
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Classical swine fever (CSF) is an ancient disease caused by the classical swine fever virus (CSFV), one member of the genus Pestivirus of the family Flaviviridae.  Now after more than a century since its first recognition, our battle with this virus/disease is far from over.  While some parts of the world have been CSF-free, reemergence from a previous CSF-free area is not unprecedented.  In parts of the world where the disease is well-under-control, the virus/disease still lingers around, poses a potential threat, and colleagues there are striving for a CSF-free status. In those CSF-free areas, we would be interested to know what is their regular practice in order not to miss any reemerging cases in its earliest time, both clinically and by the laboratory practice.  When striving for a CSF-free status or in reemergence, we would be interested to know the view of colleagues on vaccination and what measures they take in the endeavor.  In those endemic areas, we would be interested to know how CSF is expressed clinically, how it is recognized and diagnosed, and how our colleagues handle it, particularly for the prevention.  So we have much to learn and share in the veterinary community.

Been a single virus with a single serotype, the CSFV is constantly tangled with the immunity and pressure that the hosts and the environment imposed on them. Antigenic variations are constantly being selected. Cross reactivity with other related viruses and vaccine viruses needs to be differentiated. In the meantime, newer generation DIVA vaccines are being developed.  It would be interesting to know how the virus establish itself in the animal body, how the virus signals itself to gain control or co-exist within the cells, and what are the consequences in different types of cells and cellular organelles. Over the years, CSFV may disguise and express itself with other common swine pathogens clinically, for example, those also causing fever, hemorrhages, lymphoid depletion, abortion or stillbirth etc. Under various circumstances, for example, the use of vaccines or the presence of partial or non-neutralizing immunity, they may express themselves in unusual forms that are different from those the textbook tells of, and it often requires the laboratory practices to confirm its expression.

Nowadays in the wake of other currently prevailing swine diseases, the CSF/CSFV seem raises little attention on the veterinary forum.  In spite of this, veterinarians and scientists in all corners of the world are continually working, silently and diligently, trying to gain grounds on this battle.  We would like to take this opportunity, that the MDPI Inc. creates for us, to welcome colleagues to share their experience and results, whether clinical or basic, whether low tech or high tech.

Prof. Dr. Fun-In Wang
Dr. Chia-Yi Chang
Guest Editors

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Keywords

  • epidemiology
  • reemergence
  • endemic
  • wild boar
  • pathogenesis
  • atypical form
  • chronic form
  • late-onset form
  • congenital form
  • virulence
  • antigen
  • cross-reaction
  • vaccine
  • cross-protection
  • diagnosis
  • detection
  • DIVA
  • phylogenetics
  • prevention
  • control

Published Papers (16 papers)

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Editorial

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3 pages, 198 KiB  
Editorial
Classical Swine Fever: A Truly Classical Swine Disease
by Fun-In Wang and Chia-Yi Chang
Pathogens 2020, 9(9), 745; https://doi.org/10.3390/pathogens9090745 - 10 Sep 2020
Cited by 2 | Viewed by 1967
Abstract
Recent reemergence of classical swine fever (CSF) in previous CSF-free areas reminds the veterinary community of this old disease [...] Full article
(This article belongs to the Special Issue Classical Swine Fever)

Research

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11 pages, 2862 KiB  
Article
Comparison of the Pathogenicity of Classical Swine Fever Virus Subgenotype 2.1c and 2.1d Strains from China
by Genxi Hao, Huawei Zhang, Huanchun Chen, Ping Qian and Xiangmin Li
Pathogens 2020, 9(10), 821; https://doi.org/10.3390/pathogens9100821 - 07 Oct 2020
Cited by 6 | Viewed by 2013
Abstract
Classical swine fever (CSF) caused by classical swine fever virus (CSFV) is a highly contagious and devastating disease. The traditional live attenuated C-strain vaccine is widely used to control disease outbreaks in China. Since 2000, subgenotype 2.1 has become dominant in China. Here, [...] Read more.
Classical swine fever (CSF) caused by classical swine fever virus (CSFV) is a highly contagious and devastating disease. The traditional live attenuated C-strain vaccine is widely used to control disease outbreaks in China. Since 2000, subgenotype 2.1 has become dominant in China. Here, we isolated subgenotype 2.1c and 2.1d strains from CSF-suspected pigs. The genetic variations and pathogenesis of subgenotype 2.1c and 2.1d strains were investigated experimentally. We aimed to evaluate and compare the replication characteristics and clinical signs of subgenotype 2.1c and 2.1d strains with those of the typical highly virulent CSFV SM strain. In PK-15 cells, the three CSFV isolates exhibited similar replication levels but significantly lower replication levels compared with the CSFV SM strain. The experimental animal infection model showed that the pathogenicity of subgenotype 2.1c and 2.1d strains was less than that of the CSFV SM strain. According to the clinical scoring system, subgenotype 2.1c (GDGZ-2019) and 2.1d (HBXY-2019 and GXGG-2019) strains were moderately virulent. This study showed that the pathogenicity of CSFV field strains will aid in the understanding of CSFV biological characteristics and the related epidemiology. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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10 pages, 1584 KiB  
Article
Serodynamic Analysis of the Piglets Born from Sows Vaccinated with Modified Live Vaccine or E2 Subunit Vaccine for Classical Swine Fever
by Yi-Chia Li, Ming-Tang Chiou and Chao-Nan Lin
Pathogens 2020, 9(6), 427; https://doi.org/10.3390/pathogens9060427 - 29 May 2020
Cited by 5 | Viewed by 2406
Abstract
Classical swine fever (CSF) caused by the CSF virus (CSFV) is one of the most important swine diseases, resulting in huge economic losses to the pig industry worldwide. Systematic vaccination is one of the most effective strategies for the prevention and control of [...] Read more.
Classical swine fever (CSF) caused by the CSF virus (CSFV) is one of the most important swine diseases, resulting in huge economic losses to the pig industry worldwide. Systematic vaccination is one of the most effective strategies for the prevention and control of this disease. Two main CSFV vaccines, the modified live vaccine (MLV) and the subunit E2 vaccine, are recommended. In Taiwan, CSF cases have not been reported since 2006, although systemic vaccination has been practiced for 70 years. Here, we examined the sero-dynamics of the piglets born from sows that received either the CSFV MLV or the E2 vaccine and investigated in the field the correlation between the porcine reproductive and respiratory syndrome virus (PRRSV) loads and levels of CSFV antibody. A total of 1398 serum samples from 42 PRRSV-positive farms were evaluated to determine the PRRSV loads by real-time PCR and to detect CSFV antibody levels by commercial ELISA. Upon comparing the two sow vaccination protocols (CSFV MLV vaccination at 4 weeks post-farrowing versus E2 vaccination at 4–5 weeks pre-farrowing), the lowest levels of CSFV antibody were found in piglets at 5–8 and 9–12 weeks of age for the MLV and E2 groups, respectively. Meanwhile, the appropriate time window for CSFV vaccination of offspring was at 5–8 and 9–12 weeks of age in the MLV and E2 groups, respectively. There was a very highly significant negative correlation between the PRRSV load and the level of CSFV antibody in the CSFV MLV vaccination group (P < 0.0001). The PRRSV detection rate in the pigs from the MLV group (27.78%) was significantly higher than that in pigs from the E2 group (21.32%) (P = 0.011). In addition, there was a significant difference (P = 0.019) in the PRRSV detection rate at 5–8 weeks of age between the MLV (42.15%) and E2 groups (29.79%). Our findings indicate that the vaccination of CSFV MLV in piglets during the PRRSV susceptibility period at 5–8 weeks of age may be overloading the piglet’s immune system and should be a critical concern for industrial pork production in the field. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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18 pages, 2297 KiB  
Article
Foetal Immune Response Activation and High Replication Rate during Generation of Classical Swine Fever Congenital Infection
by José Alejandro Bohórquez, Sara Muñoz-González, Marta Pérez-Simó, Iván Muñoz, Rosa Rosell, Liani Coronado, Mariano Domingo and Llilianne Ganges
Pathogens 2020, 9(4), 285; https://doi.org/10.3390/pathogens9040285 - 14 Apr 2020
Cited by 10 | Viewed by 2310
Abstract
Classical swine fever virus (CSFV) induces trans-placental transmission and congenital viral persistence; however, the available information is not updated. Three groups of sows were infected at mid-gestation with either a high, moderate or low virulence CSFV strains. Foetuses from sows infected with high [...] Read more.
Classical swine fever virus (CSFV) induces trans-placental transmission and congenital viral persistence; however, the available information is not updated. Three groups of sows were infected at mid-gestation with either a high, moderate or low virulence CSFV strains. Foetuses from sows infected with high or low virulence strain were obtained before delivery and piglets from sows infected with the moderate virulence strain were studied for 32 days after birth. The low virulence strain generated lower CSFV RNA load and the lowest proportion of trans-placental transmission. Severe lesions and mummifications were observed in foetuses infected with the high virulence strain. Sows infected with the moderately virulence strain showed stillbirths and mummifications, one of them delivered live piglets, all CSFV persistently infected. Efficient trans-placental transmission was detected in sows infected with the high and moderate virulence strain. The trans-placental transmission occurred before the onset of antibody response, which started at 14 days after infection in these sows and was influenced by replication efficacy of the infecting strain. Fast and solid immunity after sow vaccination is required for prevention of congenital viral persistence. An increase in the CD8+ T-cell subset and IFN-alpha response was found in viremic foetuses, or in those that showed higher viral replication in tissue, showing the CSFV recognition capacity by the foetal immune system after trans-placental infection. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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13 pages, 1274 KiB  
Article
In Vivo Demonstration of the Superior Replication and Infectivity of Genotype 2.1 with Respect to Genotype 3.4 of Classical Swine Fever Virus by Dual Infections
by Yu-Liang Huang, Kuo-Jung Tsai, Ming-Chung Deng, Hsin-Meng Liu, Chin-Cheng Huang, Fun-In Wang and Chia-Yi Chang
Pathogens 2020, 9(4), 261; https://doi.org/10.3390/pathogens9040261 - 03 Apr 2020
Cited by 7 | Viewed by 2032
Abstract
In Taiwan, the prevalent CSFV population has shifted from the historical genotype 3.4 (94.4 strain) to the newly invading genotype 2.1 (TD/96 strain) since 1996. This study analyzed the competition between these two virus genotypes in dual infection pigs with equal and different [...] Read more.
In Taiwan, the prevalent CSFV population has shifted from the historical genotype 3.4 (94.4 strain) to the newly invading genotype 2.1 (TD/96 strain) since 1996. This study analyzed the competition between these two virus genotypes in dual infection pigs with equal and different virus populations and with maternally derived neutralizing antibodies induced by a third genotype of modified live vaccine (MLV), to simulate that occurring in natural situations in the field. Experimentally, under various dual infection conditions, with or without the presence of maternal antibodies, with various specimens from blood, oral and fecal swabs, and internal organs at various time points, the TD/96 had consistently 1.51−3.08 log higher loads than those of 94.4. A second passage of competition in the same animals further widened the lead of TD/96 as indicated by viral loads. The maternally derived antibodies provided partial protection to both wild type CSFVs and was correlated with lower clinical scores, febrile reaction, and animal mortality. In the presence of maternal antibodies, pigs could be infected by both wild type CSFVs, with TD/96 dominating. These findings partially explain the CSFV shift observed, furthering our understanding of CSFV pathogenesis in the field, and are helpful for the control of CSF. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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11 pages, 3147 KiB  
Article
Rapid Spread of Classical Swine Fever Virus among South Korean Wild Boars in Areas near the Border with North Korea
by SeEun Choe, Ra Mi Cha, Dae-Sung Yu, Ki-Sun Kim, Sok Song, Sung-Hyun Choi, Byung-Il Jung, Seong-In Lim, Bang-Hun Hyun, Bong-Kyun Park and Dong-Jun An
Pathogens 2020, 9(4), 244; https://doi.org/10.3390/pathogens9040244 - 25 Mar 2020
Cited by 13 | Viewed by 3190
Abstract
There has been a rapid increase in the number of classical swine fever (CSF) sero-positive wild boars captured near the demilitarized zone (DMZ), located the border with North Korea. In 2015–2016, few CSFV-positive antibody boars were detected; however, the number has increased steeply [...] Read more.
There has been a rapid increase in the number of classical swine fever (CSF) sero-positive wild boars captured near the demilitarized zone (DMZ), located the border with North Korea. In 2015–2016, few CSFV-positive antibody boars were detected; however, the number has increased steeply since 2017. Most occurred in the northern region of Gyeonggi before spreading slowly to Gangwon (west to east) in 2018–2019. Multi-distance spatial cluster analysis provided an indirect estimate of the time taken for CSFV to spread among wild boars: 46.7, 2.6, and 2.49 days/km. The average CSF serum neutralization antibody titer was 4–10 (log 2), and CSFV Ab B-ELISA PI values ranged from 65.5 to 111.5, regardless of the age and sex of wild boars. Full genome analysis revealed that 16 CSFV strains isolated from wild boars between 2017 and 2019 were identical to the YC16CS strain (sub-genotype 2.1d) isolated from an outbreak in breeding pigs near the border with North Korea in 2016. The rapid increase in CSF in wild boars may be due to a continuously circulating infection within hub area and increased population density. The distribution pattern of CSFV in Korean wild boars moves from west to southeast, affected by external factors, including small-scale hunting, geographical features and highways. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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13 pages, 1080 KiB  
Article
Development of a High-Throughput Serum Neutralization Test Using Recombinant Pestiviruses Possessing a Small Reporter Tag
by Madoka Tetsuo, Keita Matsuno, Tomokazu Tamura, Takasuke Fukuhara, Taksoo Kim, Masatoshi Okamatsu, Norbert Tautz, Yoshiharu Matsuura and Yoshihiro Sakoda
Pathogens 2020, 9(3), 188; https://doi.org/10.3390/pathogens9030188 - 04 Mar 2020
Cited by 11 | Viewed by 5103
Abstract
A serum neutralization test (SNT) is an essential method for the serological diagnosis of pestivirus infections, including classical swine fever, because of the cross reactivity of antibodies against pestiviruses and the non-quantitative properties of antibodies in an enzyme-linked immunosorbent assay. In conventional SNTs, [...] Read more.
A serum neutralization test (SNT) is an essential method for the serological diagnosis of pestivirus infections, including classical swine fever, because of the cross reactivity of antibodies against pestiviruses and the non-quantitative properties of antibodies in an enzyme-linked immunosorbent assay. In conventional SNTs, an immunoperoxidase assay or observation of cytopathic effect after incubation for 3 to 7 days is needed to determine the SNT titer, which requires labor-intensive or time-consuming procedures. Therefore, a new SNT, based on the luciferase system and using classical swine fever virus, bovine viral diarrhea virus, and border disease virus possessing the 11-amino-acid subunit derived from NanoLuc luciferase was developed and evaluated; this approach enabled the rapid and easy determination of the SNT titer using a luminometer. In the new method, SNT titers can be determined tentatively at 2 days post-infection (dpi) and are comparable to those obtained by conventional SNTs at 3 or 4 dpi. In conclusion, the luciferase-based SNT can replace conventional SNTs as a high-throughput antibody test for pestivirus infections. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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12 pages, 3197 KiB  
Article
Pathogenicity and Genetic Characterization of Vietnamese Classical Swine Fever Virus: 2014–2018
by SeEun Choe, Van Phan Le, Jihye Shin, Jae-Hoon Kim, Ki-Sun Kim, Sok Song, Ra Mi Cha, Gyu-Nam Park, Thi Lan Nguyen, Bang-Hun Hyun, Bong-Kyun Park and Dong-Jun An
Pathogens 2020, 9(3), 169; https://doi.org/10.3390/pathogens9030169 - 28 Feb 2020
Cited by 16 | Viewed by 3313
Abstract
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, [...] Read more.
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). Full article
(This article belongs to the Special Issue Classical Swine Fever)
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11 pages, 3781 KiB  
Article
Dynamics of Classical Swine Fever Spread in Wild Boar in 2018–2019, Japan
by Norikazu Isoda, Kairi Baba, Satoshi Ito, Mitsugi Ito, Yoshihiro Sakoda and Kohei Makita
Pathogens 2020, 9(2), 119; https://doi.org/10.3390/pathogens9020119 - 13 Feb 2020
Cited by 31 | Viewed by 3572
Abstract
The prolongation of the classic swine fever (CSF) outbreak in Japan in 2018 was highly associated with the persistence and widespread of the CSF virus (CSFV) in the wild boar population. To investigate the dynamics of the CSF outbreak in wild boar, spatiotemporal [...] Read more.
The prolongation of the classic swine fever (CSF) outbreak in Japan in 2018 was highly associated with the persistence and widespread of the CSF virus (CSFV) in the wild boar population. To investigate the dynamics of the CSF outbreak in wild boar, spatiotemporal analyses were performed. The positive rate of CSFV in wild boar fluctuated dramatically from March to June 2019, but finally stabilized at approximately 10%. The Euclidean distance from the initial CSF notified farm to the farthest infected wild boar of the day constantly increased over time since the initial outbreak except in the cases reported from Gunma and Saitama prefectures. The two-month-period prevalence, estimated using integrated nested Laplace approximation, reached >80% in half of the infected areas in March–April 2019. The area affected continued to expand despite the period prevalence decreasing up to October 2019. A large difference in the shapes of standard deviational ellipses and in the location of their centroids when including or excluding cases in Gunma and Saitama prefectures indicates that infections there were unlikely to have been caused simply by wild boar activities, and anthropogenic factors were likely involved. The emergence of concurrent space–time clusters in these areas after July 2019 indicated that CSF outbreaks were scattered by this point in time. The results of this epidemiological analysis help explain the dynamics of the spread of CSF and will aid in the implementation of control measures, including bait vaccination. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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15 pages, 2304 KiB  
Article
Adverse Effects of Classical Swine Fever Virus LOM Vaccine and Jeju LOM Strains in Pregnant Sows and Specific Pathogen-Free Pigs
by SeEun Choe, Jae-Hoon Kim, Ki-Sun Kim, Sok Song, Ra Mi Cha, Wan-Choul Kang, Hyeun-Ju Kim, Gyu-Nam Park, Jihye Shin, Hyoung-Nam Jo, In-Soo Cho, Bang-Hun Hyun, Bong-Kyun Park and Dong-Jun An
Pathogens 2020, 9(1), 18; https://doi.org/10.3390/pathogens9010018 - 23 Dec 2019
Cited by 13 | Viewed by 3239
Abstract
In Jeju island of South Korea, a classical swine fever (CSF) non-vaccinated region, many pig farmers insisted on abortion and stillbirth in pregnant sows and high mortality of suckling/weaning piglets by circulating CSF virus from 2014 to 2018. We investigated whether CSF viruses [...] Read more.
In Jeju island of South Korea, a classical swine fever (CSF) non-vaccinated region, many pig farmers insisted on abortion and stillbirth in pregnant sows and high mortality of suckling/weaning piglets by circulating CSF virus from 2014 to 2018. We investigated whether CSF viruses isolated from pigs in Jeju Island (Jeju LOM) have recovered their pathogenicity by conducting experiments using pregnant sows and specific pathogen-free (SPF) pigs. The CSF modified live LOM vaccine (MLV-LOM) and Jeju LOM strains induced abortion and stillbirth in pregnant sows. Viral antigens were detected in the organs of fetuses and stillborn piglets in the absence of specific pathological lesions associated with the virulent CSF virus in both groups (MLV-LOM and Jeju LOM strain). However, antigen was detected in one newborn piglet from a sow inoculated with a Jeju LOM strain, suggesting that it may cause persistent infections in pigs. SPF pigs inoculated with the MLV-LOM or Jeju LOM strains were asymptomatic, but virus antigen was detected in several organ and blood samples. Virus shedding in both groups of animals was not detected in the feces or saliva until 21 days post inoculation. The serum concentration of the three major cytokines, IFN-α, TNF-α, and IL-10, known to be related to lymphocytopenia, were similar in both groups when the MLV-LOM or Jeju LOM strains were inoculated into SPF pigs. In conclusion, Jeju LOM strains exhibited most of the characteristics of the MLV-LOM in pigs and resulted in the same adverse effects as the MLV-LOM strain. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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13 pages, 2756 KiB  
Article
Inactivation of Classical Swine Fever Virus in Porcine Serum Samples Intended for Antibody Detection
by Denise Meyer, Anja Petrov and Paul Becher
Pathogens 2019, 8(4), 286; https://doi.org/10.3390/pathogens8040286 - 05 Dec 2019
Cited by 6 | Viewed by 3648
Abstract
Shipping of serum samples that were taken from pigs infected with classical swine fever (CSF) virus is frequently requested with the objective of serological analyses, not only for diagnostic purposes but also for exchange of reference materials that are used as control material [...] Read more.
Shipping of serum samples that were taken from pigs infected with classical swine fever (CSF) virus is frequently requested with the objective of serological analyses, not only for diagnostic purposes but also for exchange of reference materials that are used as control material of diagnostic assays. On the basis of the fact that an outbreak with CSF is associated with enormous economic losses, biological safety during the exchange of reference material is of great importance. The present study aimed to establish a pragmatic approach for reliable CSF virus (CSFV) inactivation in serum without impairing antibody detection. Considering the fact that complement inactivation through heating is routinely applied, the basic idea was to combine heat treatment with the dilution of serum in a detergent containing buffer in order to facilitate the inactivation process. The results show that treatment of serum samples with phosphate buffered saline-Tween20 (final concentration = 0.15%) along with incubation at 56 °C for 30 min inactivated CSFV and such treatment with ≤ 0.25% PBS-Tween20 does not impair subsequent antibody detection by ELISA or virus neutralization test. This minimizes the risk of virus contamination and represents a valuable contribution to a safer CSF diagnosis on a national and international level. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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14 pages, 2574 KiB  
Article
Impact of a Live Attenuated Classical Swine Fever Virus Introduced to Jeju Island, a CSF-Free Area
by SeEun Choe, Jae-Hoon Kim, Ki-Sun Kim, Sok Song, Wan-Choul Kang, Hyeon-Ju Kim, Gyu-Nam Park, Ra Mi Cha, In-Soo Cho, Bang-Hun Hyun, Bong-Kyun Park and Dong-Jun An
Pathogens 2019, 8(4), 251; https://doi.org/10.3390/pathogens8040251 - 20 Nov 2019
Cited by 15 | Viewed by 3251
Abstract
Here, we examine the effects of LOM(Low virulence of Miyagi) strains isolated from pigs (Jeju LOM strains) of Jeju Island, where vaccination with a live attenuated classical swine fever (CSF) LOM vaccine strain was stopped. The circulation of the Jeju LOM strains was [...] Read more.
Here, we examine the effects of LOM(Low virulence of Miyagi) strains isolated from pigs (Jeju LOM strains) of Jeju Island, where vaccination with a live attenuated classical swine fever (CSF) LOM vaccine strain was stopped. The circulation of the Jeju LOM strains was mainly caused by a commercial swine erysipelas (Erysipelothrix rhusiopathiae) vaccine mixed with a LOM vaccine strain, which was inoculated into pregnant sows of 20 pig farms in 2014. The Jeju LOM strain was transmitted to 91 pig farms from 2015 to 2018. A histopathogenic investigation was performed for 25 farms among 111 farms affected by the Jeju LOM strain and revealed pigs infected with the Jeju LOM strain in combination with other pathogens, which resulted in the abortion of fetuses and mortality in suckling piglets. Histopathologic examination and immunohistochemical staining identified CSF-like lesions. Our results also confirm that the main transmission factor for the Jeju LOM strain circulation is the vehicles entering/exiting farms and slaughterhouses. Probability estimates of transmission between cohabiting pigs and pigs harboring the Jeju LOM strain JJ16LOM-YJK08 revealed that immunocompromised pigs showed horizontal transmission (r = 1.22). In a full genome analysis, we did not find genetic mutation on the site that is known to relate to pathogenicity between Jeju LOM strains (2014–2018) and the commercial LOM vaccine strain. However, we were not able to determine whether the Jeju LOM strain (2014–2018) is genetically the same virus as those of the commercial LOM vaccine due to several genetic variations in structure and non-structure proteins. Therefore, further studies are needed to evaluate the pathogenicity of the Jeju LOM strain in pregnant sow and SPF pigs and to clarify the characteristics of Jeju LOM and commercial LOM vaccine strains. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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12 pages, 3478 KiB  
Article
Role of Wild Boar in the Spread of Classical Swine Fever in Japan
by Satoshi Ito, Cristina Jurado, Jaime Bosch, Mitsugi Ito, José Manuel Sánchez-Vizcaíno, Norikazu Isoda and Yoshihiro Sakoda
Pathogens 2019, 8(4), 206; https://doi.org/10.3390/pathogens8040206 - 24 Oct 2019
Cited by 39 | Viewed by 5228
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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Review

Jump to: Editorial, Research

17 pages, 653 KiB  
Review
Recent Advances in the Diagnosis of Classical Swine Fever and Future Perspectives
by Lihua Wang, Rachel Madera, Yuzhen Li, David Scott McVey, Barbara S. Drolet and Jishu Shi
Pathogens 2020, 9(8), 658; https://doi.org/10.3390/pathogens9080658 - 15 Aug 2020
Cited by 19 | Viewed by 5472
Abstract
Classical swine fever (CSF) is a highly contagious viral disease of pigs, including wild boar. It is regarded as one of the major problems in the pig industry as it is still endemic in many regions of the world and has the potential [...] Read more.
Classical swine fever (CSF) is a highly contagious viral disease of pigs, including wild boar. It is regarded as one of the major problems in the pig industry as it is still endemic in many regions of the world and has the potential to cause devastating epidemics, particularly in countries free of the disease. Rapid and reliable diagnosis is of utmost importance in the control of CSF. Since clinical presentations of CSF are highly variable and may be confused with other viral diseases in pigs, laboratory diagnosis is indispensable for an unambiguous diagnosis. On an international level, well-established diagnostic tests of CSF such as virus isolation, fluorescent antibody test (FAT), antigen capture antibody enzyme-linked immunosorbent assay (ELISA), reverse-transcription polymerase chain reaction (RT-PCR), virus neutralization test (VNT), and antibody ELISA have been described in detail in the OIE Terrestrial Manual. However, improved CSF diagnostic methods or alternatives based on modern technologies have been developed in recent years. This review thus presents recent advances in the diagnosis of CSF and future perspectives. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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19 pages, 3931 KiB  
Review
Classical Swine Fever Virus Biology, Clinicopathology, Diagnosis, Vaccines and a Meta-Analysis of Prevalence: A Review from the Indian Perspective
by Yashpal Singh Malik, Sudipta Bhat, O. R. Vinodh Kumar, Ajay Kumar Yadav, Shubhankar Sircar, Mohd Ikram Ansari, Dilip Kumar Sarma, Tridib Kumar Rajkhowa, Souvik Ghosh and Kuldeep Dhama
Pathogens 2020, 9(6), 500; https://doi.org/10.3390/pathogens9060500 - 22 Jun 2020
Cited by 17 | Viewed by 4897
Abstract
Classical swine fever (CSF) is an economically significant, multi-systemic, highly contagious viral disease of swine world over. The disease is notifiable to the World Organization for Animal Health (OIE) due to its enormous consequences on porcine health and the pig industry. In India, [...] Read more.
Classical swine fever (CSF) is an economically significant, multi-systemic, highly contagious viral disease of swine world over. The disease is notifiable to the World Organization for Animal Health (OIE) due to its enormous consequences on porcine health and the pig industry. In India, the pig population is 9.06 million and contributes around 1.7% of the total livestock population. The pig industry is not well organized and is mostly concentrated in the eastern and northeastern states of the country (~40% of the country’s population). Since the first suspected CSF outbreak in India during 1944, a large number of outbreaks have been reported across the country, and CSF has acquired an endemic status. As of date, there is a scarcity of comprehensive information on CSF from India. Therefore, in this review, we undertook a systematic review to compile and evaluate the prevalence and genetic diversity of the CSF virus situation in the porcine population from India, targeting particular virus genes sequence analysis, published reports on prevalence, pathology, and updates on indigenous diagnostics and vaccines. The CSF virus (CSFV) is genetically diverse, and at least three phylogenetic groups are circulating throughout the world. In India, though genotype 1.1 predominates, recently published reports point toward increasing evidence of co-circulation of sub-genotype 2.2 followed by 2.1. Sequence identities and phylogenetic analysis of Indian CSFV reveal high genetic divergence among circulating strains. In the meta-analysis random-effects model, the estimated overall CSF prevalence was 35.4%, encompassing data from both antigen and antibody tests, and region-wise sub-group analysis indicated variable incidence from 25% in the southern to nearly 40% in the central zone, eastern, and northeastern regions. A country-wide immunization approach, along with other control measures, has been implemented to reduce the disease incidence and eliminate the virus in time to come. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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13 pages, 1352 KiB  
Review
Apoptosis, Autophagy, and Pyroptosis: Immune Escape Strategies for Persistent Infection and Pathogenesis of Classical Swine Fever Virus
by Sheng-ming Ma, Qian Mao, Lin Yi, Ming-qiu Zhao and Jin-ding Chen
Pathogens 2019, 8(4), 239; https://doi.org/10.3390/pathogens8040239 - 16 Nov 2019
Cited by 16 | Viewed by 6072
Abstract
Classical swine fever (CSF) is a severe acute infectious disease that results from classical swine fever virus (CSFV) infection, which leads to serious economic losses in the porcine industry worldwide. In recent years, numerous studies related to the immune escape mechanism of the [...] Read more.
Classical swine fever (CSF) is a severe acute infectious disease that results from classical swine fever virus (CSFV) infection, which leads to serious economic losses in the porcine industry worldwide. In recent years, numerous studies related to the immune escape mechanism of the persistent infection and pathogenesis of CSFV have been performed. Remarkably, several independent groups have reported that apoptosis, autophagy, and pyroptosis play a significant role in the occurrence and development of CSF, as well as in the immunological process. Apoptosis, autophagy, and pyroptosis are the fundamental biological processes that maintain normal homeostatic and metabolic function in eukaryotic organisms. In general, these three cellular biological processes are always understood as an immune defense response initiated by the organism after perceiving a pathogen infection. Nevertheless, several viruses, including CSFV and other common pathogens such as hepatitis C and influenza A, have evolved strategies for infection and replication using these three cellular biological process mechanisms. In this review, we summarize the known roles of apoptosis, autophagy, and pyroptosis in CSFV infection and how viruses manipulate these three cellular biological processes to evade the immune response. Full article
(This article belongs to the Special Issue Classical Swine Fever)
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