African Swine Fever: Epidemiology, Design of New Diagnostic Methods and Vaccine Development

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Vaccines and Therapeutic Developments".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 28214

Special Issue Editor


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Guest Editor
INIA-CISA (Spanish National Agrarian and Food Research Institute- Animal Health Research Centre), 28040 Madrid, Spain
Interests: veterinary virus epidemiology; risk assessment

Special Issue Information

Dear Colleagues,

The control of African swine fever (ASF) is a priority worldwide. Present in 3 continents, the ASF virus continues to spread among the domestic and wild pig populations of different countries, proving to be hard to contain given the absence of vaccines or treatments to reduce the burden of infection. In recent years, the interest in obtaining safe and effective vaccines has significantly increased, providing a glimmer of hope to the swine farming community to prevent the consequences of this deadly notifiable disease as well as to decrease the enormous cost associated with the prolonged control measures currently necessary to eradicate this insidious infection. Vaccine development against ASF is growing, and several vaccine prototypes are being tested for domestic pigs and for wild boar. Together with the vaccines, new diagnostic tests must be developed that enable differentiating infected from vaccinated animals (DIVA tests).

However, the use or not of vaccination as a measure to control ASF depends not only on vaccine characteristics, but also on the assessment of the population immunity status, the characteristics of the population at risk of infection, the potential commercial restrictions or the influence of season and climate on wild boar baits, and bait uptake, among others. In short, it requires a correct identification of the different possible scenarios, strategies to vaccinate as many animals at risk as possible in a timely manner, taking a cost–benefit analysis into consideration, and means of verifying the success of vaccination and to be able to declare freedom from disease, all of which face several challenges. Identifying the extent of spread among infected wild boar or assessing the immunity status of a population requires an intensive level of active and passive surveillance as well as a deep knowledge of wild boar ecology, behavior, and movement patterns. Similarly, surveillance and disease control are harder in remote areas, in areas with many small farms, in extensive farms or if unregistered marketing takes place. ASF is a transboundary disease, and as such, it requires transboundary actions and efforts to control it. The risk of reintroduction needs to be constantly assessed. Any disease control needs the participation of all stakeholders to be a success, and very different stakeholders are gathered around ASF control, from hunters to the swine industry and its different production systems, including subsistence farming, as well as economic interests of countries.

The purpose of this Special Issue is to focus on updated aspects of ASF epidemiology, design of new diagnostic methods, and vaccine development that contribute to control and ultimately eradicate the disease in different scenarios.

Dr. Marta Martínez-Avilés
Guest Editor

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Keywords

  • disease control
  • eradication
  • vaccination strategies
  • cost–benefit analysis
  • risk assessment
  • surveillance
  • immunity
  • diagnostics
  • wild boar
  • swine
  • domestic pigs
  • virus

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Published Papers (8 papers)

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Editorial

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2 pages, 191 KiB  
Editorial
African Swine Fever: Epidemiology, the Design of New Diagnostic Methods, and Vaccine Development
by Marta Martínez-Avilés
Pathogens 2023, 12(8), 1042; https://doi.org/10.3390/pathogens12081042 - 15 Aug 2023
Cited by 2 | Viewed by 1393
Abstract
African swine fever (ASF) is a pandemic viral disease that poses a major threat to the health of wild and domestic pigs, national economies, and subsistence livelihoods around the world [...] Full article

Research

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15 pages, 1063 KiB  
Article
Taking a Promising Vaccine Candidate Further: Efficacy of ASFV-G-ΔMGF after Intramuscular Vaccination of Domestic Pigs and Oral Vaccination of Wild Boar
by Paul Deutschmann, Tessa Carrau, Julia Sehl-Ewert, Jan Hendrik Forth, Elisenda Viaplana, Jose Carlos Mancera, Alicia Urniza, Martin Beer and Sandra Blome
Pathogens 2022, 11(9), 996; https://doi.org/10.3390/pathogens11090996 - 31 Aug 2022
Cited by 19 | Viewed by 3860
Abstract
African swine fever (ASF) is a pandemic threat to the global pig industry and wild suids. A safe and efficacious vaccine could monumentally assist in disease eradication. In the past years, promising live attenuated vaccine candidates emerged in proof-of-concept experiments, among which was [...] Read more.
African swine fever (ASF) is a pandemic threat to the global pig industry and wild suids. A safe and efficacious vaccine could monumentally assist in disease eradication. In the past years, promising live attenuated vaccine candidates emerged in proof-of-concept experiments, among which was “ASFV-G-∆MGF”. In our study, we tested the vaccine candidate in three animal experiments intramuscularly in domestic pigs and orally in wild boar. Further, a macrophage-grown vaccine virus and a virus grown on permanent cells could be employed. Irrespective of the production system of the vaccine virus, a two-dose intramuscular immunization could induce close-to-sterile immunity with full clinical protection against challenge infection. After oral immunization, 50% of the vaccinees seroconverted and all responders were completely protected against subsequent challenge. All nonresponders developed ASF upon challenge with two acute lethal infections and two mild and transient courses. The latter results show a lower efficiency after oral administration that would have to be taken into consideration when designing vaccination-based control measures. Overall, our findings confirm that “ASFV-G-∆MGF” is a most promising vaccine candidate that could find its way into well-organized and controlled immunization campaigns. Further research is needed to characterize safety aspects and define possible improvements of oral efficiency. Full article
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10 pages, 916 KiB  
Article
Development of a Real-Time Recombinase Polymerase Amplification Assay for the Rapid Detection of African Swine Fever Virus Genotype I and II
by Titov Ilya, Sezim Monoldorova, Shin-Seok Kang, Seungri Yun, Hyeon-Seop Byeon, Nefedeva Mariia and Bo-Young Jeon
Pathogens 2022, 11(4), 439; https://doi.org/10.3390/pathogens11040439 - 5 Apr 2022
Cited by 9 | Viewed by 2614
Abstract
African swine fever (ASF) is a contagious viral disease in pigs and wild boars which poses a major threat to the pig industry. Rapid and accurate diagnosis is necessary to control ASF. Hence, we developed a rapid diagnostic method using a recombinase polymerase [...] Read more.
African swine fever (ASF) is a contagious viral disease in pigs and wild boars which poses a major threat to the pig industry. Rapid and accurate diagnosis is necessary to control ASF. Hence, we developed a rapid diagnostic method using a recombinase polymerase amplification (RPA) assay targeting the conserved sequences of CP204L (p30) thatcan rapidly detect ASF virus (ASFV) genotype strains I and II. The lower detection limit of the real-time RPA assay was 5 × 101 copies per reaction. The real-time RPA assay effectively detected ASFV isolates and clinical specimens belonging to ASFV genotypes I and II. The sensitivity and specificity of the assay were 96.8% (95% confidence interval (CI): 83.3–99.9) and 100% (95% CI: 88.4–100.0), respectively. The agreement between the real-time RPA assay and a reference commercial real-time quantitative polymerase chain reaction (qPCR) was 100%. The real-time RPA assay had a detection time of 6.0 min (95% CI: 5.7–6.2), which was significantly shorter than that of qPCR (49 min; 95% CI: 47.4–50.6; p < 0.001). Thus, the developed real-time RPA assay is a rapid and accurate diagnostic tool for detecting ASFV genotypes I and II. Full article
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13 pages, 276 KiB  
Article
Evaluation of a Lateral Flow Assay for Rapid Detection of African Swine Fever Virus in Multiple Sample Types
by Chukwunonso Onyilagha, Kelvin Nguyen, Pam D. Luka, Ularamu Hussaini, Adeyinka Adedeji, Theophilus Odoom and Aruna Ambagala
Pathogens 2022, 11(2), 138; https://doi.org/10.3390/pathogens11020138 - 24 Jan 2022
Cited by 8 | Viewed by 3786
Abstract
Antibody-based lateral flow assay (LFA) is a quick and inexpensive tool used to detect pathogens in field samples, especially in hard-to-reach remote areas that may have limited access to central laboratories during an outbreak or surveillance. In this study, we investigated the ability [...] Read more.
Antibody-based lateral flow assay (LFA) is a quick and inexpensive tool used to detect pathogens in field samples, especially in hard-to-reach remote areas that may have limited access to central laboratories during an outbreak or surveillance. In this study, we investigated the ability of a commercially available LFA, PenCheck®, to detect African swine fever virus (ASFV) in clinical samples derived from pigs infected with highly virulent ASFV strains. The assay was specific and positively identified the majority of pigs showing high fever during the early stages (between 3 and 5 days) of infection. PenCheck® LFA also detected ASFV in serum and tissue samples collected from pigs that succumbed to experimental ASFV infection and whole blood, plasma, and tissue samples from the field. The limit of detection of the assay was ASFV titer 107.80 TCID50/mL, corresponding to ASFV real-time PCR values below 23 Ct. Although the sensitivity of the assay is less than that of the laboratory-based real-time PCR assays, the results obtained with the PenCheck® LFA in this study suggest that it can be used as a herd-level, field-deployable, and easy-to-use diagnostic tool to identify ASF-affected farms when access to portable molecular assays or central laboratories is not possible. Full article
17 pages, 2164 KiB  
Article
African Swine Fever Survey in a European Context
by Ana de la Torre, Jaime Bosch, José Manuel Sánchez-Vizcaíno, Satoshi Ito, Carolina Muñoz, Irene Iglesias and Marta Martínez-Avilés
Pathogens 2022, 11(2), 137; https://doi.org/10.3390/pathogens11020137 - 23 Jan 2022
Cited by 16 | Viewed by 5180
Abstract
African swine fever (ASF) is currently the most threatening disease for domestic and wild pigs worldwide. Wild boar has been the main affected species in all EU countries except for Romania, where most notifications occur in domestic pigs. The spread of ASF in [...] Read more.
African swine fever (ASF) is currently the most threatening disease for domestic and wild pigs worldwide. Wild boar has been the main affected species in all EU countries except for Romania, where most notifications occur in domestic pigs. The spread of ASF in wild boar is challenging to control; risk factors are harder to identify and establish than in domestic pigs, which, together with an underestimation of the disease and the lack of treatment or an effective vaccine, are hindering control and eradication efforts. We distributed two online questionnaires, one for domestic pigs and one for wild boar, to experts of different background and countries in Europe, to explore risk factors in relation to ASF control connected to farming, hunting, trade, the environment, and domestic pig and wild boar populations. Overall, wild boar movements were estimated to pose the highest risk of ASF introduction and spread. The movement of pork and pork products for own consumption also ranked high. Here we explored, in addition to the assessment of risk pathways, the identification of risks of transmission at the domestic/wild boar interface, the importance of biosecurity practices and improved control efforts, and controversial opinions that require further attention. Full article
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10 pages, 1372 KiB  
Article
Quantitative Risk Assessment of African Swine Fever Introduction into Spain by Legal Import of Live Pigs
by Carolina Muñoz-Pérez, Jaime Bosch, Satoshi Ito, Marta Martínez-Avilés and José Manuel Sánchez-Vizcaíno
Pathogens 2022, 11(1), 76; https://doi.org/10.3390/pathogens11010076 - 8 Jan 2022
Cited by 2 | Viewed by 3143
Abstract
African swine fever (ASF) is a devastating infectious disease of pigs that is threatening the global swine industry at present. The current spread of ASF in Europe and its recent incursion into Germany pose a serious risk to Spain, one of the world’s [...] Read more.
African swine fever (ASF) is a devastating infectious disease of pigs that is threatening the global swine industry at present. The current spread of ASF in Europe and its recent incursion into Germany pose a serious risk to Spain, one of the world’s leading pig producers. A quantitative stochastic risk assessment model was developed to estimate the probability of ASF introduction into Spain via the legal import of live pigs. The results suggest a low annual probability of ASF introduction into Spain (1.07 × 10−4), the highest risk being concentrated in Central European countries (Germany, the Netherlands, Belgium, and Luxembourg) during the months of April and February. The methods and results presented herein could contribute to improving prevention and control strategies and, ultimately, would help reduce the risk of ASF introduction into Spain. Full article
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14 pages, 20101 KiB  
Article
Comparative Analysis of Full Genome Sequences of African Swine Fever Virus Isolates Taken from Wild Boars in Russia in 2019
by Ali Mazloum, Antoinette van Schalkwyk, Andrey Shotin, Alexey Igolkin, Ivan Shevchenko, Konstantin N. Gruzdev and Natalia Vlasova
Pathogens 2021, 10(5), 521; https://doi.org/10.3390/pathogens10050521 - 26 Apr 2021
Cited by 23 | Viewed by 3191
Abstract
In this study, we report on the full genome phylogenetic analysis of four ASFV isolates obtained from wild boars in Russia. These samples originated from two eastern and two western regions of Russia in 2019. Phylogenetic analysis indicated that the isolates were assigned [...] Read more.
In this study, we report on the full genome phylogenetic analysis of four ASFV isolates obtained from wild boars in Russia. These samples originated from two eastern and two western regions of Russia in 2019. Phylogenetic analysis indicated that the isolates were assigned to genotype II and grouped according to their geographical origins. The two eastern isolates shared 99.99% sequence identity with isolates from China, Poland, Belgium, and Moldova, whereas the western isolates had 99.98% sequence identity with isolates from Lithuania and the original Georgia 2007 isolate. Based on the full genome phylogenies, we identified three single locus targets, MGF-360-10L, MGF-505-9R, and I267L, that yielded the same resolving power as the full genomes. The ease of alignment and a high level of variation make these targets a suitable selection as additional molecular markers in future ASFV phylogenetic practices. Full article
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Review

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19 pages, 758 KiB  
Review
Review of the Pig-Adapted African Swine Fever Viruses in and Outside Africa
by Mary-Louise Penrith, Juanita Van Heerden, Livio Heath, Edward Okoth Abworo and Armanda D. S. Bastos
Pathogens 2022, 11(10), 1190; https://doi.org/10.3390/pathogens11101190 - 16 Oct 2022
Cited by 15 | Viewed by 3742
Abstract
The region in eastern, central and southern Africa (ECSA) where African swine fever (ASF) originated in a sylvatic cycle is home to all the p72 genotypes of ASF virus identified so far. While 20 of the 24 genotypes have been isolated from outbreaks [...] Read more.
The region in eastern, central and southern Africa (ECSA) where African swine fever (ASF) originated in a sylvatic cycle is home to all the p72 genotypes of ASF virus identified so far. While 20 of the 24 genotypes have been isolated from outbreaks in domestic pigs in the region, only five of the genotypes (I, II, VIII, IX, X) have an extended field presence associated with domestic pigs. Of the genotypes that appear to be strongly adapted to domestic pigs, two have spread beyond the African continent and have been the focus of efforts to develop vaccines against ASF. Most of the experimental ASF vaccines described do not protect against a wider spectrum of viruses and may be less useful in the event of incursions of different strains or where multiple genotypes co-exist. The other three pig-adapted strains that are currently restricted to the ECSA region might spread, and priority should be given to understanding not only the genetic and antigenic characteristics of these viruses but also their history. We review historic and current knowledge of the distribution of these five virus genotypes, and note that as was the case for genotype II, some pig-associated viruses have the propensity for geographical range expansion. These features are valuable for prioritizing vaccine-development efforts to ensure a swift response to virus escape. However, whilst ASF vaccines are critical for high-production systems, global food security relies on parallel efforts to improve biosecurity and pig production in Africa and on continued ASFV surveillance and characterisation in the ECSA region. Full article
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