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Yamashita M, Iwamoto S, Ochiai M, Yamamoto A, Sudo K, Narushima R, Nagasaka T, Saito A, Oba M, Omatsu T, Mizutani T, Yamamoto K. Pathogenicity of genotype 2.1 classical swine fever virus isolated from Japan in 2019 in pigs. Microbiol Immunol 2024; 68:267-280. [PMID: 38946035 DOI: 10.1111/1348-0421.13160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Revised: 05/13/2024] [Accepted: 06/09/2024] [Indexed: 07/02/2024]
Abstract
Classical swine fever (CSF) re-emerged in Japan in 2018 for the first time in 26 years. The disease has been known to be caused by a moderately pathogenic virus, rather than the highly pathogenic virus that had occurred in the past. However, the underlying pathophysiology remains unknown. This study conducted an experimental challenge on specific pathogen-free (SPF) pigs in a naïve state for 2, 4, and 6 weeks and confirmed the disease state during each period by clinical observation, virus detection, and pathological necropsy. We revealed the pathological changes and distribution of pathogens and virus-specific antibodies at each period after virus challenge. These results were comprehensively analyzed and approximately 70% of the pigs recovered, especially at 4- and 6-week post-virus challenge. This study provides useful information for future countermeasures against CSF by clarifying the pathogenicity outcomes in unvaccinated pigs with moderately pathogenic genotype 2.1 virus.
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Affiliation(s)
- Maiko Yamashita
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
- Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology (Cooperative Division of Veterinary Sciences), Tokyo, Japan
| | - Shoko Iwamoto
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
| | - Mariko Ochiai
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
| | - Atsushi Yamamoto
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
| | - Kasumi Sudo
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
- Livestock Industry Bureau, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
| | - Rie Narushima
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
| | - Takao Nagasaka
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
| | - Akito Saito
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
- Exotic Diseases Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, Tokyo, Japan
| | - Mami Oba
- Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology (Cooperative Division of Veterinary Sciences), Tokyo, Japan
| | - Tsutomu Omatsu
- Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology (Cooperative Division of Veterinary Sciences), Tokyo, Japan
| | - Tetsuya Mizutani
- Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology (Cooperative Division of Veterinary Sciences), Tokyo, Japan
| | - Kinya Yamamoto
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan
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Hayama Y, Sawai K, Murato Y, Yamaguchi E, Kondo S, Yamamoto T. Analysis of effective spatial range of oral vaccination against classical swine fever for wild boar. Prev Vet Med 2023; 221:106080. [PMID: 38029645 DOI: 10.1016/j.prevetmed.2023.106080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 11/15/2023] [Accepted: 11/20/2023] [Indexed: 12/01/2023]
Abstract
Classical swine fever (CSF) re-emerged in Gifu Prefecture, central Japan, in September 2018 and is currently widespread in wild boar populations. Due to its widespread in wild boars, an oral mass vaccination strategy was initiated in March 2019, employing a commercial bait vaccine that is a live attenuated vaccine. To enhance the effectiveness of oral vaccination, it is crucial to determine the vaccine's effective spatial range. This understanding is essential for devising a comprehensive vaccination strategy, which should also include a preliminary investigation of wild boar habitats before vaccination. This study aimed to estimate the effective range of oral vaccination for wild boars against CSF by analyzing the geographical relationship between immune wild boars and vaccination points within the vaccination areas in Gifu Prefecture. This study utilized oral vaccination data from April 2021 to March 2022. The prevalence of CSF infections in wild boars remained below 5% in this period, suggesting limited disease transmission and immune wild boars were considered to be induced by the effect of vaccination. Two vaccination campaigns were conducted during this period, with almost 2000 vaccination points each. To investigate the factors associated with the intensity (i.e., density) of immune wild boar, the nearest distances to a vaccination point and to a susceptible wild boar were evaluated as explanatory variables. The Rhohat procedure and point process model were utilized to analyze the relationship between the intensity of immune wild boars and the explanatory variables. The point process model revealed a significant decrease in the intensity of immune wild boars when the distance from the nearest vaccination point exceeded 500 m, indicating that the effective spatial range of bait vaccination is within 500 m of the vaccination point. Although the distance to the nearest susceptible animal did not show significance in the model, Rhohat plots indicated that the intensity of immune wild boars decreased at distances greater than 1200 m from the nearest susceptible wild boar. This finding highlights the importance of investigating susceptible wild boar populations within a range of at least 1200 m from a vaccination point before implementation. The present study revealed the effective range of oral vaccination for wild boars against CSF and indicated the importance of investigating susceptible wild boar habitats around vaccination points before the implementation of vaccination. These findings may help improve the effectiveness of oral vaccinations.
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Affiliation(s)
- Yoko Hayama
- Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
| | - Kotaro Sawai
- Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Yoshinori Murato
- Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Emi Yamaguchi
- Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Sonoko Kondo
- Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Takehisa Yamamoto
- Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
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Fukai K, Nishi T, Masujin K, Yamada M, Ikezawa M. Quantitative analysis of viremia and viral shedding in pigs infected experimentally with classical swine fever virus isolates obtained from recent outbreaks in Japan. Vet Res 2023; 54:81. [PMID: 37759265 PMCID: PMC10523739 DOI: 10.1186/s13567-023-01215-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/04/2023] [Indexed: 09/29/2023] Open
Abstract
Although classical swine fever occurred in September 2018 for the first time in 26 years, its virulence is thought to be moderate based on field observations by veterinary authorities and our previous experimental infections. We quantified viremia and viral shedding in pigs infected with recent Japanese classical swine fever virus isolates, as well as a highly virulent strain. The results show that pigs infected with the Japanese strains exhibited lower viremia and viral shedding than those infected with the highly virulent strain. However, horizontal transmission occurred in pigs infected with the Japanese strains, similar to those infected with the highly virulent strain. Additionally, viremia and neuralization antibodies coexisted in pigs infected with the Japanese strains, presenting challenges for control measures.
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Affiliation(s)
- Katsuhiko Fukai
- WOAH Reference Laboratory for Classical Swine Fever, Kodaira Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1 Josui-Honcho, Kodaira, Tokyo, 187-0022, Japan.
| | - Tatsuya Nishi
- WOAH Reference Laboratory for Classical Swine Fever, Kodaira Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1 Josui-Honcho, Kodaira, Tokyo, 187-0022, Japan
| | - Kentaro Masujin
- WOAH Reference Laboratory for Classical Swine Fever, Kodaira Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1 Josui-Honcho, Kodaira, Tokyo, 187-0022, Japan
| | - Manabu Yamada
- National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan
| | - Mitsutaka Ikezawa
- National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan
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Haplotype of Wild Korean Boars Infected by Classical Swine Fever Virus Subgenotype 2.1d. Animals (Basel) 2022; 12:ani12192670. [PMID: 36230411 PMCID: PMC9559489 DOI: 10.3390/ani12192670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 09/29/2022] [Accepted: 10/01/2022] [Indexed: 11/05/2022] Open
Abstract
Simple Summary Classical swine fever is a highly contagious disease that infects both domestic pigs and wild boars. Classical swine fever virus (CSFV) has not been detected in domestic pigs in South Korea since 2016, but has been increasing in wild boars since 2017. Two cases of CSFV subgenotype 2.1d were detected in wild Korean boars in 2011, but then no cases were detected until 2016; however, 16 cases of CSFV were detected between 2017 and 2019. In this study, we report seven CSFV-positive samples obtained from wild boars in 2020. In addition, although 13 mtDNA haplotypes were detected in wild boars in South Korea, all 25 cases of CSFV that occurred in wild boars between 2011 and 2020 were detected in animals with haplotype 01. Abstract 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.
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Yao J, Su L, Wang Q, Gao L, Xie J, He Y, Shu X, Song C, Chai J, Zhang Y, Yang S. Epidemiological investigation and phylogenetic analysis of Classical Swine Fever virus in Yunnan province from 2015 to 2021. J Vet Sci 2022; 23:e57. [PMID: 35920121 PMCID: PMC9346530 DOI: 10.4142/jvs.22042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 05/06/2022] [Accepted: 05/13/2022] [Indexed: 11/20/2022] Open
Abstract
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.
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Affiliation(s)
- Jun Yao
- Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory, Yunnan Animal Science & Veterinary Institute, Kunming 650224, China
| | - Linlin Su
- College of Animal Medicine, Yunnan Agricultural University, Kunming 650201, China
| | - Qiaoping Wang
- College of Animal Medicine, Yunnan Agricultural University, Kunming 650201, China
| | - Lin Gao
- Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory, Yunnan Animal Science & Veterinary Institute, Kunming 650224, China
| | - Jiarui Xie
- Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory, Yunnan Animal Science & Veterinary Institute, Kunming 650224, China
| | - Yuwen He
- Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory, Yunnan Animal Science & Veterinary Institute, Kunming 650224, China
| | - Xianghua Shu
- College of Animal Medicine, Yunnan Agricultural University, Kunming 650201, China
| | - Chunlian Song
- College of Animal Medicine, Yunnan Agricultural University, Kunming 650201, China
| | - Jun Chai
- College of Animal Medicine, Yunnan Agricultural University, Kunming 650201, China
| | - Yifang Zhang
- College of Animal Medicine, Yunnan Agricultural University, Kunming 650201, China
| | - Shibiao Yang
- Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory, Yunnan Animal Science & Veterinary Institute, Kunming 650224, China
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Matsuyama R, Yamamoto T, Hayama Y, Omori R. Estimation of the Lethality Rate, Recovery Rate, and Case Fatality Ratio of Classical Swine Fever in Japanese Wild Boar: An Analysis of the Epidemics From September 2018 to March 2019. Front Vet Sci 2021; 8:772995. [PMID: 34977211 PMCID: PMC8714742 DOI: 10.3389/fvets.2021.772995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 11/11/2021] [Indexed: 11/13/2022] Open
Abstract
Understanding the morbidity and lethality of diseases is necessary to evaluate the effectiveness of countermeasure against the epidemics (e.g., vaccination). To estimate them, detailed data on host population dynamics are required; however, estimating the population size for wildlife is often difficult. We aimed to elucidate the morbidity and lethality of classical swine fever (CSF) currently highly prevalent in the wild boar population in Japan. To this end, we estimated lethality rate, recovery rate, and case fatality ratio (CFR) of CSF without detailed data on the population estimates of wild boar. A mathematical model was constructed to describe the CSF dynamics and population dynamics of wild boar. We fitted the model to the (i) results of the reverse transcription polymerase chain reaction (RT-PCR) test for the CSFV gene and the (ii) results of the enzyme-linked immunosorbent assay (ELISA) test for the antibody against CSFV in sampled wild boar. In the 280 wild boar sampled from September 2018 to March 2019 in the major CSF-affected area in Japan, the lethality rate and recovery rate of CSF per week were estimated as 0.165 (95% confidence interval: 0.081–0.250) and 0.004 (0–0.009), respectively. While the estimate of lethality rate of CSF was similar with the estimates in previous studies, the recovery rate was lower than those reported previously. CFR was estimated as 0.959 (0.904–0.981) using our estimate of recovery rate. This study is the first to estimate lethality rate of CSF from the dynamics of CSF epidemics in the wild boar population. Since the value of CFR is sensitive to the value of recovery rate, the accuracy in the estimate of recovery rate is a key for the accurate estimation of CFR. A long-term transmission experiment of moderately virulent strains may lead to more accurate estimation of the recovery rate and CFR of CSF.
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Affiliation(s)
- Ryota Matsuyama
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Takehisa Yamamoto
- Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Yoko Hayama
- Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Ryosuke Omori
- International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan
- *Correspondence: Ryosuke Omori
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Oki M, Ikezawa M, Nishi T, Fukai K, Yamada M. Immunohistochemical analysis of the distribution of classical swine fever (CSF) viral antigen in boar-pig hybrids and pigs four weeks after infection. J Vet Med Sci 2021; 84:48-52. [PMID: 34789589 PMCID: PMC8810325 DOI: 10.1292/jvms.21-0226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We detected the classical swine fever virus (CSFV) antigen in three boar-pig hybrids (hybrids) and three pigs. All animals were experimentally infected with CSFV strain JPN/27/2019 to optimize diagnostic sampling and risk assessment of virus dissemination. Two hybrids died 17- and 19-days post-inoculation (dpi). The other animals were euthanized at 28 dpi. The detection of CSFV antigen at 28 dpi in epithelial cells of the apocrine sweat and sebaceous glands in the skin, salivary glands, mucosal epithelial cells in the rectum, and epithelial cells in the kidney and urinary bladder, suggests that CSFV persists in these tissues and spreads via sweat, saliva, feces, and urine for at least 4 weeks. These findings reveal that hybrids and pigs represent a high risk of virus dissemination four weeks after infection with CSFV strain JPN/27/2019. Prominent CSFV antigens were also detected in hair follicles of the skin. These results suggest that postmortem sampling of animal skin may be effective for CSF diagnosis and can be used to develop a rapid and easy diagnostic method using hair follicles.
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Affiliation(s)
| | - Mitsutaka Ikezawa
- National Institute of Animal Health, National Agriculture and Food Research Organization
| | - Tatsuya Nishi
- National Institute of Animal Health, National Agriculture and Food Research Organization
| | - Katsuhiko Fukai
- National Institute of Animal Health, National Agriculture and Food Research Organization
| | - Manabu Yamada
- National Institute of Animal Health, National Agriculture and Food Research Organization
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Nishi T, Fukai K, Kato T, Sawai K, Yamamoto T. Genome variability of classical swine fever virus during the 2018-2020 epidemic in Japan. Vet Microbiol 2021; 258:109128. [PMID: 34058522 DOI: 10.1016/j.vetmic.2021.109128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 05/20/2021] [Indexed: 11/18/2022]
Abstract
Although RNA viruses exhibit extensive sequence diversity, the mutation rate must be limited to ensure protein functions that maintain the viral life cycle. Here, we compared the whole genome sequences of 150 isolates of classical swine fever virus (CSFV), obtained from a single epidemic that occurred in Japan during 2018-2020. After the detection of the first case, the disease spread among both farm pigs and wild boars and caused severe impact on the pig industry. To evaluate the diversification of the CSFV genome that eliminated mutations negatively affecting viral transmission, the substitution sets inherited by at least two isolates were separately evaluated as shared single nucleotide variants (SNVs) or shared single amino acid variants (SAVs). Comparisons of 12 protein-coding regions indicated that the percentages of SNVs and SAVs in the multifunctional nonstructural protein NS3 were the lowest, and shared SAVs were not detected in another nonstructural protein, NS4A. This demonstrated purifying negative selection suppressing changes in the protein sequences of NS3 and NS4A during virus transmission in the field. In contrast, a high possibility of nonsynonymous substitution among shared SNVs was detected only in genes encoding the secreted protein Erns and the nonstructural protein NS2, suggesting positive selection during the epidemic. Mapping of shared SAVs to the three-dimensional structure of Erns revealed that shared SAVs were not present in the substrate-binding sites but were instead localized to the peripheral region of the protein. These data will support efforts toward the development of diagnostic methods, recombinant vaccines, and antiviral agents targeting conserved and indispensable viral genes.
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Affiliation(s)
- Tatsuya Nishi
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Tokyo, Japan
| | - Katsuhiko Fukai
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Tokyo, Japan
| | - Tomoko Kato
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Tokyo, Japan
| | - Kotaro Sawai
- Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan
| | - Takehisa Yamamoto
- Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan.
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Epidemiological analysis of classical swine fever in wild boars in Japan. BMC Vet Res 2021; 17:188. [PMID: 33975588 PMCID: PMC8111369 DOI: 10.1186/s12917-021-02891-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 04/28/2021] [Indexed: 12/03/2022] Open
Abstract
Background Classical swine fever (CSF) is a contagious disease of pigs and wild boars that is transmitted through direct/indirect contact between animals or CSF virus-contaminated fomites. When the disease re-emerged in 2018 in Japan, a CSF-infected wild boar was reported shortly after the initial pig farm outbreak; subsequently, the disease spread widely. To control the disease spread among wild boars, intensive capturing, fencing, and oral bait vaccination were implemented with concomitant virological and serological surveillance. This study aimed to describe the disease spread in the wild boar population in Japan from September 2018, when the first case was reported, to March 2020, based on the surveillance data. We conducted statistical analyses using a generalized linear mixed model to identify factors associated with CSF infection among wild boars. Moreover, we descriptively assessed the effect of oral bait vaccination, which started in March 2019 in some municipalities in the affected areas. Results We observed a faster CSF infection spread in the wild boar population in Japan compared with the CSF epidemics in European countries. The infection probability was significantly higher in dead and adult animals. The influence of the multiple rounds of oral bait vaccination was not elucidated by the statistical modeling analyses. There was a decrease and increase in the proportion of infected and immune animals, respectively; however, the immunization in piglets remained insufficient after vaccination for 1 year. Conclusions Conditions regarding the wild boar habitat, including forest continuity, higher wild boar population density, and a larger proportion of susceptible piglets, were addressed to increase the infection risk in the wild boar population. These findings could improve the national control strategy against the CSF epidemic among wild boars. Supplementary Information The online version contains supplementary material available at 10.1186/s12917-021-02891-0.
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Sawai K, Nishi T, Fukai K, Kato T, Hayama Y, Yamamoto T. Phylogenetic and phylodynamic analysis of a classical swine fever virus outbreak in Japan (2018-2020). Transbound Emerg Dis 2021; 69:1529-1538. [PMID: 33890426 DOI: 10.1111/tbed.14117] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/12/2021] [Accepted: 04/16/2021] [Indexed: 12/24/2022]
Abstract
After 26 years, another classical swine fever virus (CSFV) outbreak in domestic pigs and wild boars occurred in Japan 2018. Herein, we investigated the entry and the spatial dynamics of the CSFV outbreak in Japan using the nearly complete genomes of strains isolated from both wild boars and domestic pigs during this epidemic. Phylogenetic analysis showed that the most recent common ancestor (MRCA) of the Japanese lineage emerged 146 days (95% highest posterior density (HPD): 85-216 days) before the index case was detected. Based on epidemiological analysis, the period for the 95% HPD was 1 month earlier than the time of virus introduction into the index farm. The disease mainly spreads to the adjoining regions during the epidemic, with no spread to the nonadjacent regions. This result indicates that human activities, such as the movement of vehicles, contributed to the infection spread. As cases occurred in nonadjacent regions, the MRCA for the epidemic in the Saitama prefecture was estimated to have emerged 93 days before the date of detection in the initial farm in this region. Similarly, the MRCA for the epidemic in Okinawa prefecture, more than 1,300 km away from the other infected regions, was estimated to have emerged 34 days before the date of detection in the region's primary farm. Therefore, our results indicate that if exotic diseases emerge after a long period of absence or in a disease-free country, a longer period of time will elapse before detection, resulting in further spread. Additionally, subsequent infections occurring in regions distant from the original infected region will require less time for detection than in the original region. This study provides valuable insights into a CSFV outbreak that occurred in a previously CSFV-free country and thus beneficial in enhancing producers' awareness and allow for better preparation for infections.
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Affiliation(s)
- Kotaro Sawai
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Tatsuya Nishi
- Exotic Disease Research Station, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Japan
| | - Katsuhiko Fukai
- Exotic Disease Research Station, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Japan
| | - Tomoko Kato
- Exotic Disease Research Station, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Japan
| | - Yoko Hayama
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Takehisa Yamamoto
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
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Sudo K, Yamada M, Ochiai M, Iwamoto S, Sakaki H, Kushida C, Yamashita M, Yamamoto A, Nagasaka T, Oidemizu M, Saito A, Yamamoto K. The formation process of button ulcers in pigs experimentally infected with a subgenotype 2.1 isolate of classical swine fever virus. J Vet Med Sci 2021; 83:990-993. [PMID: 33867396 PMCID: PMC8267204 DOI: 10.1292/jvms.20-0654] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We evaluated the role of classical swine fever virus (CSFV) in the formation of button ulcers in the mucosa of the gastrointestinal tract. Histopathological and immunohistochemical analyses of pigs experimentally infected with a subgenotype 2.1 isolate of CSFV, which was isolated in Japan in 2019, revealed follicular necrosis in the submucosal mucosa-associated lymphoid tissue and herniation of crypts as factors that contribute to the development of button ulcers during CSFV infection. These findings indicate that CSFV induces follicular necrosis and is one of the causative agents of button ulcers in pigs.
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Affiliation(s)
- Kasumi Sudo
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan.,Present address: Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00153 Rome, Italy
| | - Manabu Yamada
- National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannodai, Tsukuba, Ibaraki 305-0856, Japan
| | - Mariko Ochiai
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Shoko Iwamoto
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Hajime Sakaki
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Chiho Kushida
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Maiko Yamashita
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Atsushi Yamamoto
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Takao Nagasaka
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Mikio Oidemizu
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Akito Saito
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
| | - Kinya Yamamoto
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
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12
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Genotyping and Molecular Characterization of Classical Swine Fever Virus Isolated in China during 2016-2018. Viruses 2021; 13:v13040664. [PMID: 33921513 PMCID: PMC8069065 DOI: 10.3390/v13040664] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 04/06/2021] [Accepted: 04/07/2021] [Indexed: 12/17/2022] Open
Abstract
Classical swine fever (CSF) is a highly contagious disease of swine caused by classical swine fever virus (CSFV). For decades the disease has been controlled in China by a modified live vaccine (C-strain) of genotype 1. The emergent genotype 2 strains have become predominant in China in the past years that are genetically distant from the vaccine strain. Here, we aimed to evaluate the current infectious status of CSF, and for this purpose 24 isolates of CSFV were identified from different areas of China during 2016–2018. Phylogenetic analysis of NS5B, E2 and full genome revealed that the new isolates were clustered into subgenotype 2.1d and 2.1b, while subgenotype 2.1d was predominant. Moreover, E2 and Erns displayed multiple variations in neutralizing epitope regions. Furthermore, the new isolates exhibited capacity to escape C-strain-derived antibody neutralization compared with the Shimen strain (genotype 1). Potential positive selection sites were identified in antigenic regions of E2 and Erns, which are related with antibody binding affinity. Recombination events were predicted in the new isolates with vaccine strains in the E2 gene region. In conclusion, the new isolates showed molecular variations and antigenic alterations, which provide evidence for the emergence of vaccine-escaping mutants and emphasize the need of updated strategies for CSF control.
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13
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Yamamoto T, Sawai K, Nishi T, Fukai K, Kato T, Hayama Y, Murato Y, Shimizu Y, Yamaguchi E. Subgrouping and analysis of relationships between classical swine fever virus identified during the 2018-2020 epidemic in Japan by a novel approach using shared genomic variants. Transbound Emerg Dis 2021; 69:1166-1177. [PMID: 33730417 DOI: 10.1111/tbed.14076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 03/01/2021] [Accepted: 03/15/2021] [Indexed: 11/29/2022]
Abstract
Classical swine fever (CSF) is a worldwide devastating disease of the pig industry caused by classical swine fever virus (CSFV). In September 2018, an outbreak of CSF occurred in Japan where the disease had been eradicated and was officially designated a CSF-free country since 2015. Following the detection of the first 2018 case on a farm in Gifu Prefecture, the disease spread among both farm pigs and wild boars and still continues. Epigenome analysis using whole-genome information is helpful in identifying the infection route, but the current approaches provide an insufficient resolution. In this study, a novel method of using single-nucleotide variants (SNVs) was employed to identify the associations among 158 isolates (65 from farms and 93 from wild boars). The identified groups of CSFV strains were plotted in different colours on a map, identifying the location where each strain was collected. The lack of an SNV set shared between the index case and the other strains suggested the first infection in Japan during the outbreak occurred in wild boars, not at the index farm. For the Atsumi Peninsula outbreaks, where nine farms were found infected within a 10-km radius area, the farm strains were assembled into three groups, suggesting these outbreaks resulted from at least three different infection events in this area. For the infections in the area around Saitama Prefecture, an area remote from the epicentre, strains from both the farms and wild boars were identified as being in the same group, suggesting they resulted from one viral introduction. Likewise, seven infected farms in Okinawa Prefecture, almost 1,500 km from Gifu Prefecture, were identified as being in a common, but separate group. By demonstrating the variety of transmission routes and possibility of long-distance infection, these results will help improve disease control measures.
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Affiliation(s)
- Takehisa Yamamoto
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
| | - Kotaro Sawai
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
| | - Tatsuya Nishi
- Foot and Mouth Disease Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Japan
| | - Katsuhiko Fukai
- Foot and Mouth Disease Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Japan
| | - Tomoko Kato
- Foot and Mouth Disease Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Japan
| | - Yoko Hayama
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
| | - Yoshinori Murato
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
| | - Yumiko Shimizu
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
| | - Emi Yamaguchi
- Epidemiology Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
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14
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Coronado L, Perera CL, Rios L, Frías MT, Pérez LJ. A Critical Review about Different Vaccines against Classical Swine Fever Virus and Their Repercussions in Endemic Regions. Vaccines (Basel) 2021; 9:154. [PMID: 33671909 PMCID: PMC7918945 DOI: 10.3390/vaccines9020154] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 01/31/2021] [Accepted: 02/09/2021] [Indexed: 12/24/2022] Open
Abstract
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.
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Affiliation(s)
- Liani Coronado
- National Centre for Animal and Plant Health (CENSA), OIE Collaborating Centre for Disaster Risk Reduction in Animal Health, San José de las Lajas 32700, Cuba; (L.C.); (C.L.P.); (M.T.F.)
| | - Carmen L. Perera
- National Centre for Animal and Plant Health (CENSA), OIE Collaborating Centre for Disaster Risk Reduction in Animal Health, San José de las Lajas 32700, Cuba; (L.C.); (C.L.P.); (M.T.F.)
| | - Liliam Rios
- Reiman Cancer Research Laboratory, Faculty of Medicine, University of New Brunswick, Saint John, NB E2L 4L5, Canada;
| | - María T. Frías
- National Centre for Animal and Plant Health (CENSA), OIE Collaborating Centre for Disaster Risk Reduction in Animal Health, San José de las Lajas 32700, Cuba; (L.C.); (C.L.P.); (M.T.F.)
| | - Lester J. Pérez
- Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Illinois at Urbana–Champaign, Champaign, IL 61802, USA
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15
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Xie K, Chen H, Peng B, Jin Z, Xiao W, Zhang Z, Huang B, Song Q, Tang Y. On-Site Determination of Classical Swine Fever Virus (CSFV) by a Fluorescent Microsphere-Based Lateral Flow Immunoassay Strip (FM-LFIAs) Based on Monoclonal Antibodies. ANAL LETT 2020. [DOI: 10.1080/00032719.2020.1860998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Kaixin Xie
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Hui Chen
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Bin Peng
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Zhiyuan Jin
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Wei Xiao
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Zhigang Zhang
- State Key Laboratory of Food Safety Technology for Meat Products, Xiamen Yinxiang Group, Xiamen, China
| | - Boyan Huang
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Qifang Song
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
| | - Yong Tang
- Department of Bioengineering, Guangdong Province Engineering Research Center of Antibody Drug and Immunoassay, Jinan University, Guangzhou, China
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16
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Murato Y, Hayama Y, Shimizu Y, Sawai K, Yamamoto T. Evaluation of sampling methods for effective detection of infected pig farms during a disease outbreak. PLoS One 2020; 15:e0241177. [PMID: 33091063 PMCID: PMC7580991 DOI: 10.1371/journal.pone.0241177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 10/12/2020] [Indexed: 11/19/2022] Open
Abstract
Emergency surveillance following an outbreak of transboundary animal diseases such as classical swine fever (CSF), is conducted to find another new infection as early as possible. Although larger sample sizes can help achieve higher disease surveillance sensitivity, the sample size is limited by the availability of resources in an emergency situation. Moreover, the recent CSF outbreak reported in Japan was associated with fewer clinical signs; this emphasizes the importance of detecting infected farms by surveillance. In this study, we aimed to identify effective and labor-efficient sampling methods showing high probabilities of detecting infection, by simulating infection and sampling in pigsties. We found that impartial sampling, which involves selection of pigs to be sampled from the four corners and the center of the pigsty, and random sampling showed comparable probabilities of detection. Impartial sampling involves sample collection without pig identification and random selection. Owing to its simplicity, impartial sampling is labor-efficient and thus a possible substitute for random sampling. In a group-housing pigsty, testing five pigs from five pens showed a higher detection probability than testing five pigs from one pen. These results suggest preferable surveillance methods for conducting emergency surveillance of infectious diseases.
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Affiliation(s)
- Yoshinori Murato
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Yoko Hayama
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Yumiko Shimizu
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Kotaro Sawai
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
| | - Takehisa Yamamoto
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan
- * E-mail:
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17
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Shimizu Y, Hayama Y, Murato Y, Sawai K, Yamaguchi E, Yamamoto T. Epidemiology of Classical Swine Fever in Japan-A Descriptive Analysis of the Outbreaks in 2018-2019. Front Vet Sci 2020; 7:573480. [PMID: 33195567 PMCID: PMC7536261 DOI: 10.3389/fvets.2020.573480] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 08/18/2020] [Indexed: 11/13/2022] Open
Abstract
This study describes the epidemiological characteristics of classical swine fever (CSF) outbreaks in Japan. The first case was confirmed in September 2018, 26 years after the last known case. Outbreaks occurred on 39 farms, 34 commercial farms, and 5 non-commercial farms, between September 2018 and August 2019. In this study, a descriptive analysis was conducted of the epidemiological data on the characteristics of the affected farms, clinical manifestations, intra-farm transmission, association with infected wild boars, and control measures implemented on the farms. Twenty-eight of the 34 affected commercial farms were farrow-to-finish farms. It was assumed that the major risk factors were frequent human-pig interactions and the movement of pigs between farms. Fever and leukopenia were commonly observed in infected pigs. In 12 out of 18 farms where clinical manifestations among fattening pigs was the reason for notification, death was the most frequent clinical manifestation, but the proportion of dead animals did not exceed 0.5% of the total number of animals at most of the affected farms. Therefore, the clinical form of CSF in Japan was considered to be sub-acute. Twenty-three of the 29 farms (79%) with pigs at multiple stages (i.e., piglets, fattening pigs, and sows), had infection across the multiple stages. Many of these farms were within 5 km of the site where the first infected wild boars had been discovered, suggesting that infected wild boars were the source of infection. Infections still occurred at farms that had implemented measures at their farm boundaries to prevent the introduction of the virus into their farms, such as disinfection of vehicles and people, changing boots of the workers, and installation of perimeter fences. It is necessary to continue to strengthen biosecurity measures for farms located in areas with infected wild boars and to continue monitoring the distribution of infected wild boars so that any abnormalities can be reported and inspected at an early stage.
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Affiliation(s)
- Yumiko Shimizu
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Yoko Hayama
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Yoshinori Murato
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Kotaro Sawai
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Emi Yamaguchi
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Takehisa Yamamoto
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan
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18
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Izzati UZ, Hoa NT, Lan NT, Diep NV, Fuke N, Hirai T, Yamaguchi R. Pathology of the outbreak of subgenotype 2.5 classical swine fever virus in northern Vietnam. Vet Med Sci 2020; 7:164-174. [PMID: 32781492 PMCID: PMC7840204 DOI: 10.1002/vms3.339] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 06/22/2020] [Accepted: 07/20/2020] [Indexed: 11/06/2022] Open
Abstract
Classical swine fever (CSF) is an endemic disease in southeastern Asia and is one of the most important swine diseases in Vietnam. This study was conducted to characterize the pathology of natural cases of CSF in northern Vietnam in 2018 and their genetic prevalence. A total of 10 representative pigs were collected from four provinces (Hung Yen, Ha Noi, Quang Ninh and Thai Binh) during five outbreaks and examined pathologically. The gross and histopathological findings showed the disease was expressed as the acute or the subacute to chronic form of CSF, depending on the age of the animals. The most consistently observed lesions associated with infection by the classical swine fever virus (CSFV) included lymphoid depletions in tonsils, lymph node and spleen; histiocytic hyperplasia in spleen; cerebral haemorrhage; perivascular cuffing in the brain; renal erythrodiapedesis; urothelial vacuolation and degeneration and interstitial pneumonia. The immunohistochemical findings showed a ubiquitous CSFV antigen mainly in the monocytes/macrophages and in the epithelial and endothelial cells in various organs. CSFV neurotropism was also found in the small neurons of the cerebrum and the ganglia of the myenteric plexus. Analysis of the full-length envelope protein (E2) genome sequence showed that all strains were genetically clustered into subgenotype 2.5, sharing a nucleotide identity of 94.0%-100.00%. Based on the results of this study, the strain was categorized as a moderately virulent CSFV.
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Affiliation(s)
- Uda Zahli Izzati
- Department of Veterinary Pathology, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Nguyen Thi Hoa
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
| | - Nguyen Thi Lan
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
| | - Nguyen Van Diep
- Department of Veterinary Pathology, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan.,Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
| | - Naoyuki Fuke
- Department of Veterinary Pathology, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Takuya Hirai
- Department of Veterinary Pathology, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Ryoji Yamaguchi
- Department of Veterinary Pathology, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
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19
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Fukai K, Nishi T, Yamada M, Ikezawa M. Toward better control of classical swine fever in wild boars: susceptibility of boar-pig hybrids to a recent Japanese isolate and effectiveness of a bait vaccine. Vet Res 2020; 51:96. [PMID: 32736657 PMCID: PMC7393845 DOI: 10.1186/s13567-020-00821-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 07/16/2020] [Indexed: 11/22/2022] Open
Abstract
We analyzed the pathogenicity of a recent Japanese classical swine fever virus (CSFV) to wild boars via an experimental infection using boar-pig hybrids as an alternative to wild boars. We also investigated the effectiveness of a bait vaccine against the CSFV. Naïve boar-pig hybrids and pigs showed clinical signs such as fever, leucopenia, anorexia and conjunctivitis following the experimental infection. In contrast, the boar-pig hybrids administered the bait vaccine did not show any clinical signs. Our data indicated that boar-pig hybrids and domestic pigs have similar susceptibility to the recent Japanese CSFV. Additionally, the bait vaccine is effective against the CSFV.
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Affiliation(s)
- Katsuhiko Fukai
- Exotic Disease Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1 Josui-honcho, Kodaira, Tokyo, 187-0022, Japan.
| | - Tatsuya Nishi
- Exotic Disease Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1 Josui-honcho, Kodaira, Tokyo, 187-0022, Japan
| | - Manabu Yamada
- National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan
| | - Mitsutaka Ikezawa
- National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan
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20
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Ikeda T, Asano M, Kuninaga N, Suzuki M. Monitoring relative abundance index and age ratios of wild boar (Sus scrofa) in small scale population in Gifu prefecture, Japan during classical swine fever outbreak. J Vet Med Sci 2020; 82:861-865. [PMID: 32435014 PMCID: PMC7324824 DOI: 10.1292/jvms.20-0083] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the first cases of classical swine fever were reported in 2018, no studies have
explored this impact on wild boar populations in Japan. Comparing the relative abundance
indices and age ratios in the wild boar population before and after the outbreak, we
investigated the impact of classical swine fever virus on wild boar population dynamics in
August 2017–December 2019. Relative abundance indices declined from 2017 to 2019
drastically, while there were no significant differences in age ratios throughout the
study period. Consequently, wildlife managers should consider that wild boars continue to
contract classical swine fever virus, and they should intensively implement
countermeasures in agricultural lands and in pig farms, in addition to wild boar
population management.
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Affiliation(s)
- Takashi Ikeda
- Research Center for Wildlife Management, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193, Japan
| | - Makoto Asano
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193, Japan
| | - Naotoshi Kuninaga
- Research Center for Wildlife Management, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193, Japan
| | - Masatsugu Suzuki
- Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193, Japan
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21
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Hayama Y, Shimizu Y, Murato Y, Sawai K, Yamamoto T. Estimation of infection risk on pig farms in infected wild boar areas-Epidemiological analysis for the reemergence of classical swine fever in Japan in 2018. Prev Vet Med 2019; 175:104873. [PMID: 31896501 DOI: 10.1016/j.prevetmed.2019.104873] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 12/09/2019] [Accepted: 12/17/2019] [Indexed: 11/30/2022]
Abstract
In September 2018, classical swine fever (CSF) reemerged in Japan after 26 years' absence. The first case was detected at a pig farm in Gifu Prefecture, in the center of Japan, and the disease spread to both domestic pigs and wild boar (Sus scrofa). The spread of CSF in wild boar is extremely difficult to control and is thus a great threat to domestic pig farms, and understanding the transmission risk from wild boar to domestic pigs is essential to implement effective control measures that will prevent domestic pig infection. Therefore, this study elucidates the transmission risk from wild boar to domestic pigs by introducing a transmission kernel that is dependent on the distance between infected wild boar and pig farms, and then estimating the risk area of infection from wild boar by describing the transmission probability. The study used epidemiological data from Gifu Prefecture in the period from September 2018 to March 2019, including a total of 171 1-km grid cells where an infected wild boar was detected and pig farm data from 13 infected and 34 uninfected farms. The estimated infection risk area within 28 days matched well with the observed data. The risk area widened gradually during the epidemic, and at the end of March, the risk area extended over a range of approximately 75 km from east to west and 40 km from north to south (almost 3000 km2). Ten out of the 13 infected farms and four out of the 34 uninfected farms were located within the high-risk area (>60 % infection probability). In contrast, one infected farm and 18 uninfected farms were located within the low-risk area (<5 % infection probability). When several infected grid cells were detected within 5 km of a pig farm, the risk of infection from wild boar within 28 days was more than 5 %. This analysis provides an estimate of the potential spatial range over which CSF virus can spread between wild boar and domestic pig farms, and can be used to inform the early detection of CSF-suspected pigs and the strengthening of biosecurity measures that will effectively prevent and control the disease based on the infection risk level.
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Affiliation(s)
- Yoko Hayama
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan.
| | - Yumiko Shimizu
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan
| | - Yoshinori Murato
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan
| | - Kotaro Sawai
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan
| | - Takehisa Yamamoto
- Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan
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22
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Inactivation of Classical Swine Fever Virus in Porcine Serum Samples Intended for Antibody Detection. Pathogens 2019; 8:pathogens8040286. [PMID: 31817478 PMCID: PMC6963797 DOI: 10.3390/pathogens8040286] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 11/26/2019] [Accepted: 12/03/2019] [Indexed: 11/17/2022] Open
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 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.
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23
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Kameyama KI, Nishi T, Yamada M, Masujin K, Morioka K, Kokuho T, Fukai K. Experimental infection of pigs with a classical swine fever virus isolated in Japan for the first time in 26 years. J Vet Med Sci 2019; 81:1277-1284. [PMID: 31292349 PMCID: PMC6785620 DOI: 10.1292/jvms.19-0133] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Following an outbreak of classical swine fever (CSF) in Japan, 2018, CSFV JPN/1/2018 was isolated from an infected pig sample. In this study, we carried out a comparative experimental
infection in pigs using this strain and the highly virulent ALD strain and compared outcomes, including clinical manifestation, virus shedding patterns and antibody responses. Although pigs
inoculated orally or intramuscularly with JPN/1/2018 developed hyperthermia and had decreased leucocyte numbers, they survived for the whole experimental period and showed less severe
clinical signs than those infected with the ALD strain. We confirmed the presence of characteristic multifocal infarction of the margin of the spleen that arises following infection with
JPN/1/2018, albeit that this finding was not observed in all infected pigs. Both viruses efficiently spread to contact pigs in a similar manner, suggesting in transmissibility between the
two strains. Viral RNAs were detected in all clinical samples, especially whole blood samples, before the pigs developed hyperthermia until at least approximately 2 weeks after inoculation.
Our findings will be valuable for the investigations into epidemic events occurring in Japan and for establishing diagnostic strategies and control measures against CSF.
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Affiliation(s)
- Ken-Ichiro Kameyama
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
| | - Tatsuya Nishi
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
| | - Manabu Yamada
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
| | - Kentaro Masujin
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
| | - Kazuki Morioka
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
| | - Takehiro Kokuho
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
| | - Katsuhiko Fukai
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, 6-20-1, Josui-honcho, Kodaira, Tokyo 187-0022, Japan
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Postel A, Nishi T, Kameyama KI, Meyer D, Suckstorff O, Fukai K, Becher P. Reemergence of Classical Swine Fever, Japan, 2018. Emerg Infect Dis 2019; 25:1228-1231. [PMID: 30870139 PMCID: PMC6537743 DOI: 10.3201/eid2506.181578] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In September 2018, classical swine fever reemerged in Japan after 26 years, affecting domestic pigs and wild boars. The causative virus belongs to the 2.1 subgenotype, which caused repeated outbreaks in eastern and Southeast Asia. Intensive surveillance of swine and vaccination of wild boars will help control and eradicate this disease in Japan.
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25
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Zhou B. Classical Swine Fever in China-An Update Minireview. Front Vet Sci 2019; 6:187. [PMID: 31249837 PMCID: PMC6584753 DOI: 10.3389/fvets.2019.00187] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/28/2019] [Indexed: 11/17/2022] Open
Abstract
Classical swine fever (CSF) remains one of the most economically important viral diseases of domestic pigs and wild boar worldwide. The causative agent is CSF virus, it is highly contagious, with high morbidity and mortality rates; as such, it is an OIE-listed disease. Owing to a nationwide policy of vaccinations of pigs, CSF is well-controlled in China, with large-scale outbreaks rarely seen. Sporadic outbreaks are however still reported every year. In order to cope with future crises and to eradicate CSF, China should strengthen and support biosecurity measures such as the timely reporting of suspected disease, technologies for reliable diagnoses, culling infected herds, and tracing possible contacts, as well as continued vaccination and support of research into drug and genetic therapies. This mini-review summarizes the epidemiology of and control strategies for CSF in China.
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Affiliation(s)
- Bin Zhou
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
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Vuono EA, Ramirez-Medina E, Holinka LG, Baker-Branstetter R, Borca MV, Gladue DP. Interaction of Structural Glycoprotein E2 of Classical Swine Fever Virus with Protein Phosphatase 1 Catalytic Subunit Beta (PPP1CB). Viruses 2019; 11:v11040307. [PMID: 30934875 PMCID: PMC6521620 DOI: 10.3390/v11040307] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 03/22/2019] [Accepted: 03/25/2019] [Indexed: 02/06/2023] Open
Abstract
Classical swine fever virus (CSFV) E2 protein, the major virus structural glycoprotein, is an essential component of the viral envelope. E2 is involved in virus absorption, induction of a protective immune response and is critical for virulence in swine. Using the yeast two-hybrid system, we identified protein phosphatase 1 catalytic subunit beta (PPP1CB), which is part of the Protein Phosphatase 1 (PP1) complex, as a specific binding host partner for E2. We further confirmed the occurrence of this interaction in CSFV-infected swine cells by using two independent methodologies: Co-immunoprecipitation and Proximity Ligation Assay. In addition, we demonstrated that pharmacological activation of the PP1 pathway has a negative effect on CSFV replication while inhibition of the PP1 pathway or knockdown of PPP1CB by siRNA had no observed effect. Overall, our data suggests that the CSFV E2 and PPP1CB protein interact in infected cells, and that activation of the PP1 pathway decreases virus replication.
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Affiliation(s)
- Elizabeth A Vuono
- Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
- Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN 37830, USA.
| | - Elizabeth Ramirez-Medina
- Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269, USA.
| | - Lauren G Holinka
- Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
| | - Ryan Baker-Branstetter
- Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
- Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN 37830, USA.
| | - Manuel V Borca
- Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
| | - Douglas P Gladue
- Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
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