Emergence and Control of African Swine Fever

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Epidemiology of Infectious Diseases".

Deadline for manuscript submissions: 31 January 2025 | Viewed by 49405

Special Issue Editors


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Guest Editor
Foreign Animal Disease, United States Department of Agriculture, Orient Point, NY 10950, USA
Interests: evolution; pathogenesis; vaccines
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Foreign Animal Disease, United States Department of Agriculture, The Bronx, NY 10474, USA
Interests: virology; virus–host interactions; vaccines; innate immunity; RNA virus; DNA virus; foreign animal diseases
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
United States Department of Agriculture (USDA), Plum Island Animal Disease Center, Agricultural Research Service, Greenport, NY 11944, USA
Interests: porcine virology

Special Issue Information

Dear Colleagues,

African swine fever (ASF) is a highly lethal and contagious viral disease found in domestic pigs, wild boars and wild suids which has significant economic consequences. Currently, this disease is endemic in many parts of the world, but with no effective commercial vaccine for prevention and control, the threat of ASF spreading to ASF-free regions is more prominent. The recent identification of ASF in the Americas for the first time in almost 40 years demonstrates the urgent need to develop novel countermeasures to control this disease.

This Special Issue will focus on understanding the different factors associated with the emergence of African swine fever and the need to establish control strategies to mitigate the propagation of this virus worldwide.  For this purpose, the scope of this issue is open to the submission of manuscripts associated with multiple aspects of the biology of African swine fever virus, including the epidemiology, evolution, pathogenesis, vaccines, drug development and diagnostics.

This Special Issue welcomes a variety of manuscript types, including original research papers, methods papers, reviews, mini-reviews, perspectives, hypotheses and theoretical works, case reports, letters to the editor, brief research reports, commentaries, opinions, editorials and technology and codes. Authors must follow the authors’ guidelines in the preparation of their manuscripts. 

We look forward to your valuable contributions that will promote further developments in this field.

Thank you for your collaboration. 

Dr. Lauro Velazquez-Salinas
Dr. Gisselle N. Medina
Dr. Elizabeth Ramirez-Medina
Guest Editors

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Keywords

  • African swine fever (ASF)
  • epidemiology
  • evolution
  • pathogenesis
  • vaccines
  • drug development
  • diagnostics

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Published Papers (19 papers)

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13 pages, 1911 KiB  
Article
Establishment of a Suitable Diagnostic Workflow to Ensure Sensitive Detection of African Swine Fever Virus Genome in Porcine Semen
by Virginia Friedrichs, Darwin Reicks, Jeffrey J. Zimmerman, Eric A. Nelson, Carola Sauter-Louis, Martin Beer, Jane Christopher-Hennings and Sandra Blome
Pathogens 2024, 13(7), 537; https://doi.org/10.3390/pathogens13070537 - 25 Jun 2024
Viewed by 1149
Abstract
The rapid spread of African swine fever virus (ASFV), causing severe and often lethal disease in domestic pigs and Eurasian wild boar, continues to be a threat to pig populations and dependent industries. Despite scientific achievements that have deepened our understanding of ASFV [...] Read more.
The rapid spread of African swine fever virus (ASFV), causing severe and often lethal disease in domestic pigs and Eurasian wild boar, continues to be a threat to pig populations and dependent industries. Despite scientific achievements that have deepened our understanding of ASFV pathogenesis, alternative transmission routes for ASFV remain to be elucidated. We previously demonstrated the efficient transmission of ASFV from infected boars to naïve recipient gilts via artificial insemination, thereby highlighting the importance of surveillance of boar semen prior to its shipment. Since the accurate and reliable detection of even low amounts of ASFV in boar semen is key to disease prevention and control, we established a suitable diagnostic workflow to efficiently detect the ASFV genome in boar semen. Here, we assessed the sensitivity of various routine nucleic acid extraction kits as well as qPCR protocols in detecting the ASFV genome in the blood and semen of infected boars. The feasibility of the respective kits and methods for future use in boar studs was also considered. Variability in sensitivity mostly concerned samples with low to very low amounts of the ASFV genome. Ultimately, we defined a well-suited workflow for precisely detecting the ASFV genome in boar semen as early as 2 days post ASFV infection. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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9 pages, 2433 KiB  
Communication
Recombinant Vaccine Strain ASFV-G-Δ9GL/ΔUK Produced in the IPKM Cell Line Is Genetically Stable and Efficacious in Inducing Protection in Pigs Challenged with the Virulent African Swine Fever Virus Field Isolate Georgia 2010
by Elizabeth Ramirez-Medina, Ayushi Rai, Nallely Espinoza, Edward Spinard, Ediane Silva, Leeanna Burton, Jason Clark, Amanda Meyers, Alyssa Valladares, Lauro Velazquez-Salinas, Cyril G. Gay, Douglas P. Gladue and Manuel V. Borca
Pathogens 2024, 13(4), 319; https://doi.org/10.3390/pathogens13040319 - 13 Apr 2024
Viewed by 1429
Abstract
We have previously reported that the recombinant African Swine Fever (ASF) vaccine candidate ASFV-G-Δ9GL/ΔUK efficiently induces protection in domestic pigs challenged with the virulent strain Georgia 2010 (ASFV-G). As reported, ASFV-G-Δ9GL/ΔUK induces protection, while intramuscularly (IM), administered at doses of 104 HAD [...] Read more.
We have previously reported that the recombinant African Swine Fever (ASF) vaccine candidate ASFV-G-Δ9GL/ΔUK efficiently induces protection in domestic pigs challenged with the virulent strain Georgia 2010 (ASFV-G). As reported, ASFV-G-Δ9GL/ΔUK induces protection, while intramuscularly (IM), administered at doses of 104 HAD50 or higher, prevents ASF clinical disease in animals infected with the homologous ASFV g strain. Like other recombinant vaccine candidates obtained from ASFV field isolates, ASFV-G-Δ9GL/ΔUK stocks need to be produced in primary cultures of swine macrophages, which constitutes an important limitation in the production of large virus stocks at the industrial level. Here, we describe the development of ASFV-G-Δ9GL/ΔUK stocks using IPKM (Immortalized Porcine Kidney Macrophage) cells, which are derived from swine macrophages. We show that ten successive passages of ASFV-G-Δ9GL/ΔUK in IPKM cells induced small changes in the virus genome. The produced virus, ASFV-G-Δ9GL/ΔUKp10, presented a similar level of replication in swine macrophages cultures to that of the original ASFV-G-Δ9GL/ΔUK (ASFV-G-Δ9GL/ΔUKp0). The protective efficacy of ASFV-G-Δ9GL/ΔUKp10 was evaluated in pigs that were IM-inoculated with either 104 or 106 HAD50 of ASFV-G-Δ9GL/ΔUKp10. While animals inoculated with 104 HAD50 present a partial protection against the experimental infection with the virulent parental virus ASFV-G, those inoculated with 106 HAD50 were completely protected. Therefore, as was just recently reported for another ASF vaccine candidate, ASFV-G-ΔI177L, IPKM cells are an effective alternative to produce stocks for vaccine strains which only grow in swine macrophages. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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18 pages, 790 KiB  
Article
Understanding Smallholder Pigkeepers’ Awareness and Perceptions of African Swine Fever and Its Control Measures in Ukraine
by Lidiia Moskalenko, Katja Schulz, Vitalii Nedosekov, Kerli Mõtus and Arvo Viltrop
Pathogens 2024, 13(2), 139; https://doi.org/10.3390/pathogens13020139 - 3 Feb 2024
Viewed by 1790
Abstract
African swine fever (ASF) has posed a significant threat to Ukrainian pig farming since its identification in 2012. In this study, recognising the pivotal role of pigkeepers in disease control, we conducted ten focus groups involving 52 smallholders across eight regions in Ukraine. [...] Read more.
African swine fever (ASF) has posed a significant threat to Ukrainian pig farming since its identification in 2012. In this study, recognising the pivotal role of pigkeepers in disease control, we conducted ten focus groups involving 52 smallholders across eight regions in Ukraine. Using participatory methods, we revealed their awareness of ASF signs, transmission routes, preventive measures, and the perceptions of stakeholders involved in ASF control. Furthermore, we identified the smallholders’ acceptance of eradication and restriction measures, the perceived impact of zoning consequences, and their main sources of ASF information. Smallholders identified fever and skin haemorrhage as the most indicative signs of ASF and highlighted rodents as a primary transmission concern. Disinfection was seen as the most effective measure for preventing the introduction of ASF. Pigkeepers who perceived their stakeholder role in ASF control showed more trust in themselves and veterinarians than in central veterinary authorities. Farm-level ASF eradication measures were generally accepted; however, culling within the protection zone was least accepted, with economic losses listed as the most impactful consequence for pigkeepers. For ASF information, pigkeepers favour web searches and veterinarians, as well as traditional media and word-of-mouth news. This study provides valuable insights into refining the ASF communication strategies in Ukraine. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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17 pages, 4491 KiB  
Article
Pathology and Clinics of Naturally Occurring Low-Virulence Variants of African Swine Fever Emerged in Domestic Pigs in the South Caucasus
by Hranush Avagyan, Sona Hakobyan, Bagrat Baghdasaryan, Hranush Arzumanyan, Arpine Poghosyan, Nane Bayramyan, Anna Semerjyan, Mariam Sargsyan, Henry Voskanyan, Tigranuhi Vardanyan, Naira Karalyan, Lina Hakobyan, Liana Abroyan, Aida Avetisyan, Elena Karalova, Zara Semerjyan and Zaven Karalyan
Pathogens 2024, 13(2), 130; https://doi.org/10.3390/pathogens13020130 - 29 Jan 2024
Cited by 5 | Viewed by 2036
Abstract
Shortly after the establishment of African swine fever virus (ASFV) genotype II in 2007, cases of acute fatal infection were observed. However, after several years of circulation in the Eurasian region, the clinical signs of the disease changed. Currently, this disease can occur [...] Read more.
Shortly after the establishment of African swine fever virus (ASFV) genotype II in 2007, cases of acute fatal infection were observed. However, after several years of circulation in the Eurasian region, the clinical signs of the disease changed. Currently, this disease can occur acutely, subclinically, chronically, or asymptomatically. Cases of the complete recovery of infected pigs, and the disappearance of ASFV from their tissues and secretions have been described. This form of the disease first appeared in Armenia at the end of 2011. This virus was described and identified as the Dilijan2011IMB strain. The goal of our research was to study the main features of clinical, pathological, immunological, virological, and genetic parameters involved in the development of new forms of African swine fever (ASF). Chronic ASF was characterized with low titers of the virus and a decrease in the intensity of hemadsorption. Additionally, a reduced intensity in clinical symptoms and pathoanatomical results was noted. The absolute, but not the relative number of immune cells changes; the neutropenia (in bone marrow and spleen), lymphopenia (in bone marrow), lymphocytosis (only in spleen), lymphoid cell depletion (in bone marrow), and pancytopenia (in bone marrow) observed in the chronic form of ASF were less pronounced compared to in the acute form. When comparing the late stage of chronic ASF to the acute form, the key cytological indicators in the spleen, lymph nodes, and blood were less severe in the chronic stage. Bone marrow failure in the chronic form, expressed in a pronounced decrease in all cell types, generally coincided with the data in the acute form of ASF. The same data were obtained after assessing serum TNF-alpha levels. Thus, we can conclude that the chronic form of ASF occurs due to a less pronounced immune response, as well as a decrease in virus titers in the blood and tissues of infected pigs. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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17 pages, 2622 KiB  
Article
Epidemiological Assessment of African Swine Fever Spread in the Dominican Republic
by Rachel A. Schambow, Syed Hussain, Maria C. Antognoli, Silvia Kreindel, Raysa Reyes and Andres M. Perez
Pathogens 2023, 12(12), 1414; https://doi.org/10.3390/pathogens12121414 - 1 Dec 2023
Cited by 2 | Viewed by 1991
Abstract
Since African Swine Fever (ASF) was detected in the Dominican Republic in July 2021, it has negatively impacted the country’s swine industry. Assessing the epidemiological situation is crucial to helping local authorities and industry stakeholders control the disease. Here, data on 155 reported [...] Read more.
Since African Swine Fever (ASF) was detected in the Dominican Republic in July 2021, it has negatively impacted the country’s swine industry. Assessing the epidemiological situation is crucial to helping local authorities and industry stakeholders control the disease. Here, data on 155 reported outbreaks in the Dominican Republic from November 2022 to June 2023 were evaluated. Descriptive spatiotemporal analysis was performed to characterize disease distribution and spread, and between-herd R0 was calculated for the study period. The Knox test and a space–time permutation model were used to evaluate clustering. Data on clinical presentation, biosecurity measures, and suspected reasons for introduction were categorized and summarized. The majority (78%) of outbreaks occurred on backyard farms which generally had low biosecurity. Across farm types, the majority of pigs were still alive at the time of depopulation. Spatiotemporal findings and R0 estimates suggest an endemic pattern of disease geographically located centrally within the country. Clustering was detected even at small temporal and spatial distances due to outbreaks amongst neighboring backyard farms. These results provide critical information on the current state of the ASF epidemic in the Dominican Republic and will aid government officials and swine industry leaders in developing effective ASF control strategies. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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14 pages, 2820 KiB  
Article
Triplex Crystal Digital PCR for the Detection and Differentiation of the Wild-Type Strain and the MGF505-2R and I177L Gene-Deleted Strain of African Swine Fever Virus
by Kaichuang Shi, Kang Zhao, Haina Wei, Qingan Zhou, Yuwen Shi, Shenglan Mo, Feng Long, Liping Hu, Shuping Feng and Meilan Mo
Pathogens 2023, 12(9), 1092; https://doi.org/10.3390/pathogens12091092 - 28 Aug 2023
Cited by 3 | Viewed by 1663
Abstract
African swine fever (ASF) is a severe and highly contagious viral disease that affects domestic pigs and wild boars, characterized by a high fever and internal bleeding. The disease is caused by African swine fever virus (ASFV), which is prevalent worldwide and has [...] Read more.
African swine fever (ASF) is a severe and highly contagious viral disease that affects domestic pigs and wild boars, characterized by a high fever and internal bleeding. The disease is caused by African swine fever virus (ASFV), which is prevalent worldwide and has led to significant economic losses in the global pig industry. In this study, three pairs of specific primers and TaqMan probes were designed for the ASFV B646L, MGF505-2R and I177L genes. After optimizing the reaction conditions of the annealing temperature, primer concentration and probe concentration, triplex crystal digital PCR (cdPCR) and triplex real-time quantitative PCR (qPCR) were developed for the detection and differentiation of the wild-type ASFV strain and the MGF505-2R and/or I177L gene-deleted ASFV strains. The results indicate that both triplex cdPCR and triplex qPCR were highly specific, sensitive and repeatable. The assays could detect only the B646L, MGF505-2R and I177L genes, without cross-reaction with other swine viruses (i.e., PRRSV, CSFV, PCV2, PCV3, PEDV, PDCoV and PRV). The limit of detection (LOD) of triplex cdPCR was 12 copies/reaction, and the LOD of triplex qPCR was 500 copies/reaction. The intra-assay and inter-assay coefficients of variation (CVs) for repeatability and reproducibility were less than 2.7% for triplex cdPCR and less than 1.8% for triplex qPCR. A total of 1510 clinical tissue samples were tested with both methods, and the positivity rates of ASFV were 14.17% (214/1510) with triplex cdPCR and 12.98% (196/1510) with triplex qPCR, with a coincidence rate of 98.81% between the two methods. The positivity rate for the MGF505-2R gene-deleted ASFV strains was 0.33% (5/1510), and no I177L gene-deleted ASFV strain was found. The results indicate that triplex cdPCR and triplex qPCR developed in this study can provide rapid, sensitive and accurate methods for the detection and differentiation of the ASFV B646L, MGF505-2R and I177L genes. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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14 pages, 2117 KiB  
Article
Factors Affecting the Spread, Diagnosis, and Control of African Swine Fever in the Philippines
by Chia-Hui Hsu, Rachel Schambow, Maximino Montenegro, Ruth Miclat-Sonaco and Andres Perez
Pathogens 2023, 12(8), 1068; https://doi.org/10.3390/pathogens12081068 - 21 Aug 2023
Cited by 7 | Viewed by 10250
Abstract
African Swine Fever (ASF) is a highly contagious disease that threatens the swine industry globally. Since its introduction into the Philippines in 2019, ASF has spread extensively in both commercial and backyard farms. Here, using a mix of qualitative and quantitative methods, including [...] Read more.
African Swine Fever (ASF) is a highly contagious disease that threatens the swine industry globally. Since its introduction into the Philippines in 2019, ASF has spread extensively in both commercial and backyard farms. Here, using a mix of qualitative and quantitative methods, including conjoint and SWOT analyses, world café discussions, and multivariable regression models, the most important factors that influence the spread, diagnosis, and control of ASF in the Philippines were identified. Research findings suggest that swill or contaminated feed, inadequate biosecurity protocols, and movement of personnel were the top risk factors favoring ASF spread among farms in general. For commercial farms, contaminated vehicles and personnel were also important, whereas for backyard farms, the introduction of new pigs, environmental contamination, and poor feeding quality were relevant risk factors. Notable clinical signs of ASF in pigs include reduced feed intake, huddled behavior, and reluctance to stand. This study highlights the need for timely reporting, trust-building initiatives, and enhanced biosecurity measures to effectively manage ASF outbreaks in the country. Results here contribute to the knowledge of factors affecting ASF spread in the Philippines and can help design prevention and control measures in ASF-infected countries while enhancing preparedness in countries free from the disease. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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9 pages, 823 KiB  
Article
Whole Genome Sequencing Shows that African Swine Fever Virus Genotype IX Is Still Circulating in Domestic Pigs in All Regions of Uganda
by Rodney Okwasiimire, Joseph F. Flint, Edrine B. Kayaga, Steven Lakin, Jim Pierce, Roger W. Barrette, Bonto Faburay, Dickson Ndoboli, John E. Ekakoro, Eddie M. Wampande and Karyn A. Havas
Pathogens 2023, 12(7), 912; https://doi.org/10.3390/pathogens12070912 - 6 Jul 2023
Cited by 6 | Viewed by 1853
Abstract
Blood samples were collected from pigs at six abattoirs in the Kampala, Uganda metropolitan area from May 2021 through June 2022, and tested for African swine fever virus. Thirty-one samples with cycle threshold values < 26 from pigs with different geographic origins, clinical [...] Read more.
Blood samples were collected from pigs at six abattoirs in the Kampala, Uganda metropolitan area from May 2021 through June 2022, and tested for African swine fever virus. Thirty-one samples with cycle threshold values < 26 from pigs with different geographic origins, clinical and pathologic signs, and Ornithodoros moubata exposure underwent whole genome sequencing. The p72 gene was used to genotype the isolates, and all were found to be genotype IX; whole genome sequences to previous genotype IX isolates confirmed their similarity. Six of the isolates had enough coverage to evaluate single nucleotide polymorphisms (SNPs). Five of the isolates differed from historic regional isolates, but had similar SNPs to one another, and the sixth isolate also differed from historic regional isolates, but also differed from the other five isolates, even though they are all genotype IX. Whole genome sequencing data provide additional detail on viral evolution that can be useful for molecular epidemiology, and understanding the impact of changes in genes to disease phenotypes, and may be needed for vaccine targeting should a commercial vaccine become available. More sequencing of African swine fever virus isolates is needed in Uganda to understand how and when the virus is changing. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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9 pages, 4558 KiB  
Communication
ASF Vaccine Candidate ASFV-G-∆I177L Does Not Exhibit Residual Virulence in Long-Term Clinical Studies
by Manuel V. Borca, Elizabeth Ramirez-Medina, Ediane Silva, Ayushi Rai, Nallely Espinoza, Lauro Velazquez-Salinas and Douglas P. Gladue
Pathogens 2023, 12(6), 805; https://doi.org/10.3390/pathogens12060805 - 6 Jun 2023
Cited by 10 | Viewed by 2372
Abstract
African swine fever (ASF) is an important disease in swine currently producing a pandemic affecting pig production worldwide. Except in Vietnam, where two vaccines were recently approved for controlled use in the field, no vaccine is commercially available for disease control. Up to [...] Read more.
African swine fever (ASF) is an important disease in swine currently producing a pandemic affecting pig production worldwide. Except in Vietnam, where two vaccines were recently approved for controlled use in the field, no vaccine is commercially available for disease control. Up to now, the most effective vaccines developed are based on the use of live-attenuated viruses. Most of these promising vaccine candidates were developed by deleting virus genes involved in the process of viral pathogenesis and disease production. Therefore, these vaccine candidates were developed via the genomic modification of parental virus field strains, producing recombinant viruses and reducing or eliminating their residual virulence. In this scenario, it is critical to confirm the absence of any residual virulence in the vaccine candidate. This report describes the assessment of the presence of residual virulence in the ASFV vaccine candidate ASFV-G-∆I177L in clinical studies conducted under high virus loads and long-term observation periods. The results demonstrated that domestic pigs intramuscularly inoculated with 106 HAD50 of ASFV-G-∆I177L did not show the presence of any clinical sign associated with ASF when observed daily either 90 or 180 days after vaccination. In addition, necropsies conducted at the end of the experiment confirmed the absence of macroscopic internal lesions associated with the disease. These results corroborate the safety of using ASFV-G-∆I177L as a vaccine candidate. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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14 pages, 2184 KiB  
Article
Development of a Novel Indirect ELISA for the Serological Diagnosis of African Swine Fever Using p11.5 Protein as a Target Antigen
by Mizuki Watanabe, Tomoya Kitamura, Koji Nagata, Mitsutaka Ikezawa, Ken-ichiro Kameyama, Kentaro Masujin and Takehiro Kokuho
Pathogens 2023, 12(6), 774; https://doi.org/10.3390/pathogens12060774 - 29 May 2023
Cited by 7 | Viewed by 2236
Abstract
African swine fever is a hemorrhagic viral disease with a mortality rate of nearly 100% in pigs. Hence, it is classified as a notifiable disease by the World Organization for Animal Health. Because no field-available vaccine exists, African swine fever virus (ASFV) control [...] Read more.
African swine fever is a hemorrhagic viral disease with a mortality rate of nearly 100% in pigs. Hence, it is classified as a notifiable disease by the World Organization for Animal Health. Because no field-available vaccine exists, African swine fever virus (ASFV) control and eradication solely depend on good farm biosecurity management and rapid and accurate diagnosis. In this study, we developed a new indirect serological enzyme-linked immunosorbent assay (ELISA) using recombinant p11.5 protein from ASFV as a solid-phase target antigen. The cutoffs were determined by receiver operating curve analysis performed with serum samples obtained from naïve and infected pigs. Based on the results of a commercially available serological ELISA, the relative sensitivity and specificity of our assay were 93.4% and 94.4% (N = 166; area under the curve = 0.991; 95% confidence interval = 0.982–0.999), respectively. Furthermore, to compare the performance of the serological ELISAs, we conducted the assays on a panel of sera collected from pigs and boars experimentally infected with different ASFV isolates. The results indicated the greater sensitivity of the newly developed assay and its ability to detect anti-ASFV antibodies earlier after virus inoculation. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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12 pages, 3430 KiB  
Article
Pathological Characteristics of Domestic Pigs Orally Infected with the Virus Strain Causing the First Reported African Swine Fever Outbreaks in Vietnam
by Thi Thu Huyen Nguyen, Van Tam Nguyen, Phuong Nam Le, Nguyen Tuan Anh Mai, Van Hieu Dong, Tran Anh Dao Bui, Thi Lan Nguyen, Aruna Ambagala and Van Phan Le
Pathogens 2023, 12(3), 393; https://doi.org/10.3390/pathogens12030393 - 1 Mar 2023
Cited by 4 | Viewed by 3550
Abstract
African swine fever (ASF) is currently Vietnam’s most economically significant swine disease. The first ASF outbreak in Vietnam was reported in February 2019. In this study, VNUA/HY/ASF1 strain isolated from the first ASF outbreak was used to infect 10 eight-week-old pigs orally with [...] Read more.
African swine fever (ASF) is currently Vietnam’s most economically significant swine disease. The first ASF outbreak in Vietnam was reported in February 2019. In this study, VNUA/HY/ASF1 strain isolated from the first ASF outbreak was used to infect 10 eight-week-old pigs orally with 103 HAD50 per animal. The pigs were observed daily for clinical signs, and whole blood samples were collected from each animal for viremia detection. Dead pigs were subjected to full post-mortem analyses. All 10 pigs displayed acute or subacute clinical signs and succumbed to the infection between 10 to 27 (19.8 ± 4.66) days post-inoculation (dpi). The onset of clinical signs started around 4–14 dpi. Viremia was observed in pigs from 6–16 dpi (11.2 ± 3.55). Enlarged, hyperemic, and hemorrhagic lymph nodes, enlarged spleen, pneumonia, and hydropericardium were observed at post-mortem examinations. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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13 pages, 2462 KiB  
Article
The First Eighteen Months of African Swine Fever in Wild Boar in Saxony, Germany and Latvia—A Comparison
by Michael Richter, Katja Schulz, Tobias Elflein, Jens Achterberg, Edvīns Oļševskis, Mārtiņš Seržants, Kristīne Lamberga, Franz Josef Conraths and Carola Sauter-Louis
Pathogens 2023, 12(1), 87; https://doi.org/10.3390/pathogens12010087 - 5 Jan 2023
Cited by 7 | Viewed by 1975
Abstract
African swine fever (ASF) emerged in Latvia in 2014. In 2020, the virus has been detected in the German federal state, Saxony. In both regions, the virus was probably introduced by infected wild boar coming from affected neighboring countries. As the current ASF [...] Read more.
African swine fever (ASF) emerged in Latvia in 2014. In 2020, the virus has been detected in the German federal state, Saxony. In both regions, the virus was probably introduced by infected wild boar coming from affected neighboring countries. As the current ASF control strategy at EU level had not yet been developed at the time of ASF introduction into Latvia, disease control measures in both study areas differed over time. Assessing the course of ASF in Saxony and the implemented control strategies, the first 18 months of the ASF epidemic were epidemiologically compared between Saxony and Latvia. ASF wild boar surveillance data were analyzed and the prevalence of ASF virus-positive wild boar was estimated. For estimating the wild boar density, the numbers of wild boar per km² were calculated for the respective geographical areas. The number of samples collected from hunted wild boar and wild boar found dead was higher in Saxony. The ASF virus prevalence in Latvia was significantly higher than in Saxony, indicating that Saxony has had more time for getting prepared for dealing with an ASF incursion. Experience from other countries and the rapid implementation of new control strategies may have helped Saxony deal with ASF. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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12 pages, 2588 KiB  
Article
Transcriptome Profiling in Swine Macrophages Infected with African Swine Fever Virus (ASFV) Uncovers the Complex and Close Relationship with Host
by Zhaoyao Li, Wenxian Chen, Xiaowen Li, Keke Wu, Xinyan Wang, Weijun Wang, Yuwan Li, Lin Yi, Mingqiu Zhao, Hongxing Ding, Shuangqi Fan and Jinding Chen
Pathogens 2022, 11(12), 1411; https://doi.org/10.3390/pathogens11121411 - 24 Nov 2022
Cited by 4 | Viewed by 2352
Abstract
African swine fever virus (ASFV) is a pathogen to cause devastating and economically significant diseases in domestic and feral swine. ASFV mainly infects macrophages and monocytes and regulates its replication process by affecting the content of cytokines in the infected cells. There is [...] Read more.
African swine fever virus (ASFV) is a pathogen to cause devastating and economically significant diseases in domestic and feral swine. ASFV mainly infects macrophages and monocytes and regulates its replication process by affecting the content of cytokines in the infected cells. There is a limited understanding of host gene expression and differential profiles before and after ASFV infection in susceptible cells. In this study, RNA-seq technology was used to analyze the transcriptomic change in PAMs infected with ASFV at different time points (0 h, 12 h, 24 h). As a result, a total of 2748, 1570, and 560 genes were enriched in group V12 h vs. MOCK, V24 h vs. MOCK, and V24 h vs. V12 h, respectively. These DEGs (differentially expressed genes) in each group were mainly concentrated in the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways related to innate immunization and inflammation, including the NF-κB signaling pathway, Toll-like receptor signaling pathway, TNF signaling pathway, IL-17 signaling pathway, cytokine-cytokine receptor interaction, and chemokine signaling pathway. Furthermore, the increased levels of IL-1β, TNF-α, IKKβ, CXCL2, and TRAF2 and decreased level of IκBα were validated through the qPCR method. These results suggested that ASFV infection can activate the NF-κB signaling pathway in the early stage. In general, this study provides a theoretical basis for further understanding the pathogenesis and immune escape mechanism of ASFV. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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27 pages, 4978 KiB  
Article
Pathology of African Swine Fever in Wild Boar Carcasses Naturally Infected with German Virus Variants
by Julia Sehl-Ewert, Paul Deutschmann, Angele Breithaupt and Sandra Blome
Pathogens 2022, 11(11), 1386; https://doi.org/10.3390/pathogens11111386 - 20 Nov 2022
Cited by 7 | Viewed by 3267
Abstract
In 2020, African swine fever (ASF) was first identified in German wild boar, reaching a case number of about 4400 to date. Upon experimental infection, pathology is well documented; however, data on field infections are scarce in domestic pigs and not available from [...] Read more.
In 2020, African swine fever (ASF) was first identified in German wild boar, reaching a case number of about 4400 to date. Upon experimental infection, pathology is well documented; however, data on field infections are scarce in domestic pigs and not available from wild boar, respectively. Although the ASF viral genome is considered exceptionally stable, a total of five lineages with 10 distinct virus variants of genotype II have emerged in Eastern Germany. To investigate the pathology in naturally infected wild boar and to evaluate virus variants II, III and IV for their virulence, wild boar carcasses were obtained from three different outbreak areas. The carcasses underwent virological and pathomorphological investigation. The animals revealed characteristic ASF lesions of the highest severity accompanied by bacterial infections in several cases. In particular, wild boar infected with variant IV from Spree-Neiße (SN) district showed lower viral genome loads and total viral antigen scores, but simultaneously tended to reveal more chronic lesions. Our findings indicate a protracted course of the disease at least after infection with variant IV, but need confirmation under standardized experimental conditions. There is a strong need to monitor differences in the virulence among variants to identify potential attenuation that might complicate diagnosis. In addition, veterinarians, hunters and farmers need to be made aware of less acute courses of ASF to consider this as an important differential to chronic classical swine fever. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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Review

Jump to: Research, Other

16 pages, 486 KiB  
Review
Advancement in the Antigenic Epitopes and Vaccine Adjuvants of African Swine Fever Virus
by Qiong Wu, Chang Li, Bo Zhu, Jiajia Zhu, Keli Yang, Zewen Liu, Wei Liu, Ting Gao, Fangyan Yuan, Rui Guo, Yongxiang Tian and Danna Zhou
Pathogens 2024, 13(8), 706; https://doi.org/10.3390/pathogens13080706 - 21 Aug 2024
Viewed by 1585
Abstract
African swine fever virus (ASFV), a highly virulent double-stranded DNA virus, poses a significant threat to global pig farming, with mortality rates in domestic pigs reaching up to 100%. Originating in Kenya in 1921, ASFV has since proliferated to Western Europe, Latin America, [...] Read more.
African swine fever virus (ASFV), a highly virulent double-stranded DNA virus, poses a significant threat to global pig farming, with mortality rates in domestic pigs reaching up to 100%. Originating in Kenya in 1921, ASFV has since proliferated to Western Europe, Latin America, Eastern Europe, and most recently China in 2018, resulting in substantial global agricultural losses. Antigenic epitopes, recognized by the immune system’s T cells and B cells, are pivotal in antiviral immune responses. The identification and characterization of these antigenic epitopes can offer invaluable insights into the immune response against ASFV and aid in the development of innovative immunotherapeutic strategies. Vaccine adjuvants, substances that amplify the body’s specific immune response to antigens, also play a crucial role. This review provides an overview of the progress in studying T/B-cell epitopes in ASFV proteins and ASFV vaccine adjuvants, highlighting their role in the immune response and potential use in new vaccine development. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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Other

Jump to: Research, Review

9 pages, 1273 KiB  
Brief Report
Glycerol Monolaurate Inhibits Wild-Type African Swine Fever Virus Infection in Porcine Macrophages
by Joshua A. Jackman, Erik Arabyan, Hovakim Zakaryan and Charles C. Elrod
Pathogens 2023, 12(10), 1193; https://doi.org/10.3390/pathogens12101193 - 25 Sep 2023
Cited by 1 | Viewed by 1625
Abstract
Naturally abundant antimicrobial lipids, such as fatty acids and monoglycerides, that disrupt membrane-enveloped viruses are promising mitigants to inhibit African swine fever virus (ASFV). Among mitigant candidates in this class, glycerol monolaurate (GML) has demonstrated particularly high antiviral activity against laboratory-adapted ASFV strains. [...] Read more.
Naturally abundant antimicrobial lipids, such as fatty acids and monoglycerides, that disrupt membrane-enveloped viruses are promising mitigants to inhibit African swine fever virus (ASFV). Among mitigant candidates in this class, glycerol monolaurate (GML) has demonstrated particularly high antiviral activity against laboratory-adapted ASFV strains. However, there is an outstanding need to further determine the effects of GML on wild-type ASFV strains, which can have different virulence levels and sensitivities to membrane-disrupting compounds as compared to laboratory-adapted strains. Herein, we investigated the antiviral effects of GML on a highly virulent strain of a wild-type ASFV isolate (Armenia/07) in an in vitro porcine macrophage model. GML treatment caused a concentration-dependent reduction in viral infectivity, and there was a sharp transition between inactive and active GML concentrations. Low GML concentrations had negligible effect on viral infectivity, whereas sufficiently high GML concentrations caused a >99% decrease in viral infectivity. The concentration onset of antiviral activity matched the critical micelle concentration (CMC) value of GML, reinforcing that GML micelles play a critical role in enabling anti-ASFV activity. These findings validate that GML can potently inhibit wild-type ASFV infection of porcine macrophages and support a biophysical explanation to guide antimicrobial lipid performance optimization for pathogen mitigation applications. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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8 pages, 231 KiB  
Brief Report
Evaluation of the Efficacy of Commercial Disinfectants against African Swine Fever Virus
by Lorraine Frost, Matthew Tully, Linda Dixon, Hayley M. Hicks, Jessica Bennett, Isobel Stokes, Laura Marsella, Simon Gubbins and Carrie Batten
Pathogens 2023, 12(7), 855; https://doi.org/10.3390/pathogens12070855 - 21 Jun 2023
Cited by 2 | Viewed by 1982
Abstract
African swine fever (ASF) is an economically important disease due to high morbidity and mortality rates and the ability to affect all ages and breeds of pigs. Biosecurity measures to prevent the spread of the causative agent, African swine fever virus (ASFV), include [...] Read more.
African swine fever (ASF) is an economically important disease due to high morbidity and mortality rates and the ability to affect all ages and breeds of pigs. Biosecurity measures to prevent the spread of the causative agent, African swine fever virus (ASFV), include prescriptive cleaning and disinfection procedures. The aim of this study was to establish the biocidal effects of twenty-four commercially available disinfectants including oxidizing agents, acids, aldehydes, formic acids, phenol, and mixed-class chemistries against ASFV. The products were prepared according to the manufacturer’s instructions and a suspension assay was performed with ASFV strain, BA71V using Vero cells (African green monkey cells) to test efficacy in reducing ASFV infection of cells. Generally, disinfectants containing formic acid and phenolic compounds, as well as oxidizing agents reduced viral titers of ASFV by over 4 log10 at temperatures ranging from 4 °C to 20 °C. Hydrogen peroxide, aldehyde, and quaternary ammonium compounds containing disinfectants were cytotoxic, limiting the detection of viral infectivity reductions to less than 4 log10. These preliminary results can be used to target research on disinfectants which contain active ingredients with known efficacy against ASFV under conditions recommended for the country where their use will be applied. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
9 pages, 1568 KiB  
Brief Report
The Presence of Virus Neutralizing Antibodies Is Highly Associated with Protection against Virulent Challenge in Domestic Pigs Immunized with ASFV live Attenuated Vaccine Candidates
by Ediane B. Silva, Peter W. Krug, Elizabeth Ramirez-Medina, Alyssa Valladares, Ayushi Rai, Nallely Espinoza, Douglas P. Gladue and Manuel V. Borca
Pathogens 2022, 11(11), 1311; https://doi.org/10.3390/pathogens11111311 - 8 Nov 2022
Cited by 9 | Viewed by 2566
Abstract
African swine fever virus (ASFV) is currently producing a pandemic affecting a large area of Eurasia, and more recently, the Dominican Republic in the Western Hemisphere. ASFV is a large and structurally complex virus with a large dsDNA genome encoding for more than [...] Read more.
African swine fever virus (ASFV) is currently producing a pandemic affecting a large area of Eurasia, and more recently, the Dominican Republic in the Western Hemisphere. ASFV is a large and structurally complex virus with a large dsDNA genome encoding for more than 150 genes. Live attenuated virus strains can induce protection in domestic swine against disease produced by homologous virulent parental viruses. The roles of the different immune mechanisms induced by the attenuated strains in protection still need to be understood. In particular, the role of ASFV neutralizing antibody in protection still is an important controversial issue to be elucidated. Here we present the development of a novel methodology to detect virus neutralizing antibodies based on the reduction of virus infectivity in a Vero cell adapted ASFV strain. The described method was used to assess levels of virus neutralizing antibodies in domestic swine inoculated with live attenuated ASFV. Results demonstrated a high association between the presence of virus neutralizing antibodies and protection in 84 animals immunized with the recombinant vaccine candidates ASFV-G-Δ9GL/ΔUK or ASFV-G-ΔI177L. To our knowledge, this is the first report demonstrating an association between virus neutralizing antibodies and protection against virulent challenge in such a large number of experimental individuals. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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9 pages, 6547 KiB  
Brief Report
Genetic Characterization of the Central Variable Region in African Swine Fever Virus Isolates in the Russian Federation from 2013 to 2017
by Ali Mazloum, Antoinette Van Schalkwyk, Roman Chernyshev, Andrey Shotin, Fedor I. Korennoy, Alexey Igolkin and Alexander Sprygin
Pathogens 2022, 11(8), 919; https://doi.org/10.3390/pathogens11080919 - 15 Aug 2022
Cited by 7 | Viewed by 1919
Abstract
African swine fever virus (ASFV), classified as genotype II, was introduced into Georgia in 2007, and from there, it spread quickly and extensively across the Caucasus to Russia, Europe and Asia. The molecular epidemiology and evolution of these isolates are predominantly investigated by [...] Read more.
African swine fever virus (ASFV), classified as genotype II, was introduced into Georgia in 2007, and from there, it spread quickly and extensively across the Caucasus to Russia, Europe and Asia. The molecular epidemiology and evolution of these isolates are predominantly investigated by means of phylogenetic analysis based on complete genome sequences. Since this is a costly and time-consuming endeavor, short genomic regions containing informative polymorphisms are pursued and utilized instead. In this study, sequences of the central variable region (CVR) located within the B602L gene were determined for 55 ASFV isolates submitted from 526 active African swine fever (ASF) outbreaks occurring in 23 different regions across the Russian Federation (RF) between 2013 and 2017. The new sequences were compared to previously published data available from Genbank, representing isolates from Europe and Asia. The sequences clustered into six distinct groups. Isolates from Estonia clustered into groups 3 and 4, whilst sequences from the RF were divided into the remaining four groups. Two of these groups (5 and 6) exclusively contained isolates from the RF, while group 2 included isolates from Russia as well as Chechnya, Georgia, Armenia, Azerbaijan and Ukraine. In contrast, group 1 was the largest, containing sequences from the RF, Europe and Asia, and was represented by the sequence from the first isolate in Georgia in 2007. Based on these results, it is recommended that the CVR sequences contain significant informative polymorphisms to be used as a marker for investigating the epidemiology and spread of genotype II ASFVs circulating in the RF, Europe and Asia. Full article
(This article belongs to the Special Issue Emergence and Control of African Swine Fever)
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