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African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids

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A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Pigs".

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 18647

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Dr. Juanita Van Emmenes

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Transboundary Animal Diseases Programme, Agricultural Research Council-Onderstepoort Veterinary Institute, Onderstepoort 0110, South Africa
Interests: nucleic acid extraction; PCR; enzymes; molecular virology; gel electrophoresis; cell culture; electrophoresis; RNA; microbiology; African swine fever; foot-and-mouth disease
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Armanda Bastos

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Department of Zoology & Entomology, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
Interests: veterinary virology; transboundary animal diseases; vector-borne and zoonotic diseases; wildlife infectious diseases; molecular diagnostics; molecular epidemiology; wildlife conservation; one health
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

African swine fever (ASF) is a contagious viral disease with mortality rates of almost 100% in domestic pigs and European wild boars. In contrast, wild African suids such as warthogs and bush pigs are generally asymptomatic. As one of the most widely consumed meats, pork offers an affordable and low-input source of high-quality protein, particularly in resource-constrained settings. Efforts to control the disease by interrupting transmission pathways rely on a comprehensive understanding of the factors driving spillover between sylvatic hosts and domestic suids, along with those limiting control once the virus has been introduced to domestic pigs. Whilst a number of universal factors are known to contribute to inefficient control in pigs, including late detection, limited funds for compensation and animal husbandry practices, drivers of inter-species transmission and multi-host spread are less well understood and are likely to differ regionally. This Special Issue attempts to address knowledge gaps in the transmission and spread of ASF in endemic and newly affected areas by addressing a broad range of ASFV infection dynamics, including, immune response, transmission pathways and virus pathogenesis in pigs. In addition, approaches shown to mitigate risk and to limit spillover and spread, inclusive of virus detection methods suited to resource-constrained settings that are heavily impacted by ASF, are particularly welcome.

Dr. Juanita Van Heerden
Prof. Dr. Armanda Bastos
Guest Editors

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Keywords

ASF
ASFV
transmission pathways
risk factors
pathogenesis
host immune responses
molecular epidemiology
novel mitigation strategies

Published Papers (11 papers)

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Research

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15 pages, 1427 KiB

Open AccessArticle

Retrospective Multi-Locus Sequence Analysis of African Swine Fever Viruses by “PACT” Confirms Co-Circulation of Multiple Outbreak Strains in Uganda

by Tonny Kabuuka, Henry Mulindwa, Armanda D. S. Bastos, Juanita van Heerden, Livio Heath and Folorunso O. Fasina

Animals 2024, 14(1), 71; https://doi.org/10.3390/ani14010071 - 24 Dec 2023

Viewed by 1379

Abstract

African swine fever (ASF) is a haemorrhagic fever of swine that severely constrains pig production, globally. In Uganda, at least 388 outbreaks of ASF were documented from 2001 to 2012. We undertook a retrospective serological and molecular survey of ASF virus (ASFV) using banked samples collected from seven districts (Pallisa, Lira, Abim, Nebbi, Kabarole, Kibaale, and Mukono) of Uganda. Six assays (ELISA for antibody detection, diagnostic p72 gene PCR and genomic amplification, and sequencing of four gene regions (p72 [P], p54 [A], CVR of the 9RL-ORF [C], and TK [T]), hereinafter referred to as P-A-C-T (PACT)) were evaluated. Antibodies to ASFV were detected in the Abim district (6/25; 24.0%), and the remainder of the serum samples were negative (187/193; 96.9%). For the tissue samples, ASFV detection by assay was 8.47% for P, 6.78% for A, 8.47% for C, and 16.95% for T. The diagnostic PCR (p72 gene) detected seven positive animals from four districts, whereas the TK assay detected ten positives from all seven districts. In addition to the superior detection capability of TK, two virus variants were discernible, whereas CVR recovered three variants, and p72 and p54 sequencing each identified a single variant belonging to genotype IX. Our results indicate that dependence on serology alone underestimates ASF positivity in any infected region, that multi-locus sequence analysis provides better estimates of outbreak strain diversity, and that the TK assay is superior to the WOAH-prescribed conventional p72 diagnostic PCR, and warrants further investigation. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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15 pages, 4572 KiB

Open AccessArticle

Predicting Disparity between ASF-Managed Areas and Wild Boar Habitats: A Case of South Korea

by Chanwoo Ko, Dongwook W. Ko and Wonhee Cho

Animals 2023, 13(22), 3482; https://doi.org/10.3390/ani13223482 - 11 Nov 2023

Viewed by 1020

Abstract

African swine fever (ASF) is a highly contagious viral disease affecting both domestic and wild boars. Since its first outbreak in South Korea in 2019, substantial efforts have been made to prevent ASF transmission by reducing the wild boar population and eliminating infected carcasses; however, the persistence of ASF transmission has posed challenges to these efforts. To improve ASF management strategies, the limitations of current management strategies must be identified by considering disparities between wild boar habitats and ASF-managed areas with environmental and anthropogenic characteristics of wild boars and their management strategies. Here, ensemble species distribution models were used to estimate wild boar habitats and potential ASF-managed areas, with elevation, distance to urban areas, and Normalized Difference Vegetation Index as important variables. Binary maps of wild boar habitats and potential ASF-managed areas were generated using the maxSSS as the threshold criterion. Disparity areas of ASF management were identified by overlying regions evaluated as wild boar habitats with those not classified as ASF-managed areas. Dense forests near urban regions like Chungcheongbuk-do, Gyeongsangbuk-do, and Gyeongsangnam-do were evaluated as disparity areas having high risk of ASF transmission. These findings hold significant potential for refining ASF management strategies and establishing proactive control measures. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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18 pages, 1946 KiB

Open AccessArticle

The Influencing Factors of “Post-African Swine Fever” Pig Farm Biosecurity: Evidence from Sichuan Province, China

by Huan Wang, Meijun Chen, Ziyao Guo, Yangyang Shen, Yufan Chen, Ting Luo, Yuying Liu, Jianqiang Li, Fang Wang and Jiangjun Wan

Animals 2023, 13(19), 3053; https://doi.org/10.3390/ani13193053 - 28 Sep 2023

Cited by 1 | Viewed by 1325

Abstract

Effective biosecurity measures are crucial in controlling and preventing major pig diseases, ultimately ensuring farm income and social stability. This study extracted data from 205 farmer surveys in Sichuan Province, China, to construct a biosecurity index system for pig farms. The biosecurity levels of pig farms were evaluated using a projection pursuit method to identify weak areas. The Tobit model was then utilized to determine the factors that influenced the biosecurity levels. The results indicated that the overall biosecurity levels of the pig farms were low. The study found that the average biosecurity score among farms was 0.61, with a minimum score of 0.37 and a maximum score of 0.89 (on a scale of 0 to 1). These results suggest that there are significant differences in biosecurity levels among the farms. The study also found that the scores for first-level indicators related to breeding environment management, as well as second-level indicators related to personnel management and awareness of African swine fever prevention and control, were significantly lower than scores for other indicators in the farmers’ biosecurity systems. This study investigated the factors influencing biosecurity on farms and found that technical training, farm size, income share, production organization, and government inspections had a significant impact on the level of biosecurity implemented. This study emphasizes the significance of biosecurity in enhancing pig farm biosecurity and its role in improving farm resilience to major animal diseases like African swine fever. It also provides valuable insights for policymakers to make informed decisions regarding related policies. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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24 pages, 3449 KiB

Open AccessArticle

African Swine Fever in Wild Boar: German Hunters’ Perception of Surveillance and Control—A Questionnaire Study

by Lisa Rogoll, Katja Schulz, Franz J. Conraths and Carola Sauter-Louis

Animals 2023, 13(18), 2813; https://doi.org/10.3390/ani13182813 - 05 Sep 2023

Viewed by 1080

Abstract

Since the first occurrence of African swine fever (ASF) in wild boar in Germany in 2020, the disease has primarily affected the wild boar population in the eastern part of the country close to the border with Poland. Local hunters play a crucial role in implementing surveillance and control. To evaluate their perceptions of existing control measures and analyze regional differences between hunters from ASF-affected and non-affected regions, a questionnaire study was conducted among the German hunting community. Hunters from non-affected areas held a more optimistic view regarding the effectiveness of control measures compared to hunters from affected areas. However, control measures that hinder hunting were generally perceived as ineffective. Measures that collided with hunters’ understanding of fair hunting practices were regarded as controversial. Financial incentives and reducing bureaucracy were the most favored approaches to increase hunters’ participation. Moreover, the possibility of eating or selling the meat of hunted wild boar and the provision of infrastructure for implementing ASF control were considered motivating. Thus, this study highlights the importance of compensating hunters and addressing their concerns to maintain their engagement in ASF control. To enhance compliance with controversial measures, thoughtful communication and raising awareness are essential. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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24 pages, 1030 KiB

Open AccessArticle

Dynamic Analysis and Optimal Control of Fractional Order African Swine Fever Models with Media Coverage

by Ruiqing Shi, Yihong Zhang and Cuihong Wang

Animals 2023, 13(14), 2252; https://doi.org/10.3390/ani13142252 - 09 Jul 2023

Viewed by 1206

Abstract

African swine fever is a highly contagious virus that causes pig disease. Its onset process is short, but the mortality rate is as high as 100%. There are still no effective drugs that have been developed to treat African swine fever, and prevention and control measures are currently the best means to avoid infection in pig herds. In this paper, two fractional order mathematical models with media coverage are constructed to describe the transmission of African swine fever. The first model is a basic model with media coverage, and no control measures are considered. For this model, the reproduction number is obtained by using the next generation matrix method. Then, the sufficient conditions for the existence and stability of two equilibriums are obtained. Based on the first model, the second model is established incorporating two control measures. By using Pontryagin’s maximal principle, the optimal control solution is derived. After that, some numerical simulations are performed for the two models to verify the theoretical results. Both the qualitative analysis and numerical results indicate that timely media coverage combined with disinfection control measures is crucial to preventing the spread of disease. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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17 pages, 3253 KiB

Open AccessArticle

Identification of Potential miRNA-mRNA Regulatory Network Associated with Regulating Immunity and Metabolism in Pigs Induced by ASFV Infection

by Zhongbao Pang, Shiyu Chen, Shuai Cui, Wenzhu Zhai, Ying Huang, Xintao Gao, Yang Wang, Fei Jiang, Xiaoyu Guo, Yuxin Hao, Wencai Li, Lei Wang, Hongfei Zhu, Jiajun Wu and Hong Jia

Animals 2023, 13(7), 1246; https://doi.org/10.3390/ani13071246 - 04 Apr 2023

Cited by 2 | Viewed by 1617

Abstract

African swine fever (ASF) is a devastating infectious disease in domestic pigs caused by African swine fever virus (ASFV) with a mortality rate of about 100%. However, the understanding of the interaction between ASFV and host is still not clear. In this study, the expression differences and functional analysis of microRNA (miRNA) in porcine peripheral blood lymphocytes of ASFV infected pigs and healthy pigs were compared based on Illumina high-throughput sequencing, then the GO and KEGG signal pathways were analyzed. The miRNA related to immunity and inflammation were screened, and the regulatory network of miRNA-mRNA was drawn. A total of 70 differentially expressed miRNAs were found (p ≤ 0.05). Of these, 45 were upregulated and 25 were downregulated in ASFV-infected pigs vs. healthy pigs. A total of 8179 mRNA genes targeted by these 70 differentially expressed miRNA were predicted, of which 1447 mRNA genes were targeted by ssc-miR-2320-5p. Five differentially expressed miRNA were validated by RT-qPCR, which were consistent with the RNA-Seq results. The GO analysis revealed that a total of 30 gene functions were significantly enriched, including 7 molecular functions (MF), 13 cellular components (CC), and 10 biological processes (BP). The KEGG enrichment analysis revealed that the differentially expressed genes were significantly enriched in pathways related to immunity, inflammation, and various metabolic processes, in which a total of two downregulated miRNAs after infection and eight upregulated miRNAs related to immunity and inflammation were screened in ASFV-infected pigs vs. healthy pigs. The network of miRNA-mRNA showed that the mRNA target genes were strongly regulated by ssc-miR-214, ssc-miR-199b-3p, and ssc-miR-199a-3p. The mRNA target genes were enriched into the MAPK signaling pathway, Toll-like receptor signaling pathway, TNF signaling pathway, and IL-17 signaling pathway by using a KEGG enrichment analysis. Therefore, ASFV could regulate immunity and metabolism-related pathways in infected pigs by inducing differential expression of miRNAs. These results provided a new basis for further elucidating the interactions between ASFV and the host as well as the immunity regulation mechanisms of ASFV, which will be conducive to better controlling ASF. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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14 pages, 275 KiB

Open AccessArticle

Factors Influencing Disease Prevention and Control Behaviours of Hog Farmers

by Jiamei Wang and Xiangdong Hu

Animals 2023, 13(5), 787; https://doi.org/10.3390/ani13050787 - 22 Feb 2023

Cited by 4 | Viewed by 2696

Abstract

Animal diseases are a serious threat to animal husbandry production and diet health, and effective prevention and control measures need to be explored. This study investigates the factors influencing the adoption of biosecurity prevention and the control behaviours of hog farmers towards African swine fever and provides appropriate recommendations. Using research data from Sichuan, Hubei, Jiangsu, Tianjin, Liaoning, Jilin, and Hebei, we employed a binary logistic model to empirically analyse these factors. Regarding individual farmer characteristics, male farmers emphasised biosecurity prevention and control in farms, with higher education actively influencing the adoption of prevention and control measures. Farmers who received technical training were actively inclined to adopt such behaviours. Furthermore, the longer the duration of farming, the more probable the farmers were to neglect biosecurity prevention and control. However, the bigger and more specialised the farm, the more inclined they were to adopt prevention and control behaviours. With respect to disease prevention and control awareness, the more risk-averse the farmers were, the more they actively adopted epidemic prevention behaviours. As the awareness of epidemic risk increased, the farmers tended to adopt active epidemic prevention behaviours by reporting suspected outbreaks. The following policy recommendations were made: learning about epidemic prevention and improving professional skills; large-scale farming, specialised farming; and timely dissemination of information to raise risk awareness. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

13 pages, 2219 KiB

Open AccessArticle

Estimation of a Within-Herd Transmission Rate for African Swine Fever in Vietnam

by Van Phan Le, Nguyen Thi Lan, Jose Tobias Canevari, Juan Pablo Villanueva-Cabezas, Pawin Padungtod, Thi Bich Ngoc Trinh, Van Tam Nguyen, Caitlin N. Pfeiffer, Madalene V. Oberin, Simon M. Firestone and Mark A. Stevenson

Animals 2023, 13(4), 571; https://doi.org/10.3390/ani13040571 - 06 Feb 2023

Cited by 5 | Viewed by 2134

Abstract

We describe results from a panel study in which pigs from a 17-sow African swine fever (ASF) positive herd in Thái Bình province, Vietnam, were followed over time to record the date of onset of ASF signs and the date of death from ASF. Our objectives were to (1) fit a susceptible-exposed-infectious-removed disease model to the data with transmission coefficients estimated using approximate Bayesian computation; (2) provide commentary on how a model of this type might be used to provide decision support for disease control authorities. For the outbreak in this herd, the median of the average latent period was 10 days (95% HPD (highest posterior density interval): 2 to 19 days), and the median of the average duration of infectiousness was 3 days (95% HPD: 2 to 4 days). The estimated median for the transmission coefficient was 3.3 (95% HPD: 0.4 to 8.9) infectious contacts per ASF-infectious pig per day. The estimated median for the basic reproductive number, R₀, was 10 (95% HPD: 1.1 to 30). Our estimates of the basic reproductive number R₀ were greater than estimates of R₀ for ASF reported previously. The results presented in this study may be used to estimate the number of pigs expected to be showing clinical signs at a given number of days following an estimated incursion date. This will allow sample size calculations, with or without adjustment to account for less than perfect sensitivity of clinical examination, to be used to determine the appropriate number of pigs to examine to detect at least one with the disease. A second use of the results of this study would be to inform the equation-based within-herd spread components of stochastic agent-based and hybrid simulation models of ASF. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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13 pages, 3177 KiB

Open AccessArticle

Simulating Hunting Effects on the Wild Boar Population and African Swine Fever Expansion Using Agent-Based Modeling

by Chanwoo Ko, Wonhee Cho, Byungmook Hwang, Byungwoo Chang, Wanmo Kang and Dongwook W. Ko

Animals 2023, 13(2), 298; https://doi.org/10.3390/ani13020298 - 14 Jan 2023

Cited by 2 | Viewed by 2450

Abstract

African swine fever (ASF) is a viral hemorrhagic fever fatal to animals of the Suidae family. It has spread from Africa to Europe and Asia, causing significant damage to wildlife and domesticated pig production. Since the first confirmed case in South Korea in September 2019, the number of infected wild boars has continued to increase, despite quarantine fences and hunting operations. Hence, new strategies are needed for the effective control of ASF. We developed an agent-based model (ABM) to estimate the ASF expansion area and the efficacy of infection control strategies. In addition, we simulated the agents’ (wild boars) behavior and daily movement range based on their ecological and behavioral characteristics, by applying annual hunting scenarios from past three years (2019.09–2022.08). The results of the simulation based on the annual changes in the number of infected agents and the ASF expansion area showed that the higher the hunting intensity, the smaller the expansion area (24,987 km² at 0% vs. 3533 km² at 70%); a hunting intensity exceeding 70% minimally affected the expansion area. A complete removal of agents during the simulation period was shown to be possible. In conclusion, an annual hunting intensity of 70% should be maintained to effectively control ASF. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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Review

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16 pages, 293 KiB

Open AccessReview

African Swine Fever: A Review of Current Disease Management Strategies and Risks Associated with Exhibition Swine in the United States

by Hannah J. Cochran, Angela M. Bosco-Lauth, Franklyn B. Garry, I. Noa Roman-Muniz and Jennifer N. Martin

Animals 2023, 13(23), 3713; https://doi.org/10.3390/ani13233713 - 30 Nov 2023

Cited by 1 | Viewed by 1049

Abstract

African swine fever is a high-consequence foreign animal disease endemic to sub-Saharan Africa and the island of Sardinia. The U.S. is the world’s third largest pork producer, and ASF introduction would severely disrupt the pork supply chain, emphasizing the need to protect market access for U.S. proteins. However, niche producers raising swine intended for exhibition may not follow stringent biosecurity protocols, and livestock show circuits may promote untracked animal movement across the country, potentially exacerbating virus’ spread in the event of ASF incursion into the U.S. Youth membership in state or national swine organizations offers a route for outreach and educational activities to enhance foreign animal disease preparedness, and adult presence at swine exhibitions allows a wide variety of programming for all ages to better serve all levels of understanding. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

14 pages, 972 KiB

Open AccessReview

African Swine Fever: The State of the Art in Italy

by Silvia Pavone, Carmen Iscaro, Annalisa Dettori and Francesco Feliziani

Animals 2023, 13(19), 2998; https://doi.org/10.3390/ani13192998 - 22 Sep 2023

Cited by 4 | Viewed by 1489

Abstract

African swine fever (ASF) is a severe viral disease of domestic pigs and Eurasian wild boars (Sus scrofa) caused by the African swine fever virus (ASFV). ASF is endemic in sub-Saharan Africa, where 24 genotypes of the virus have been reported. Between the late 1950s and the early 1980s, genotype I ASFV emerged in Europe, including Italy. In June 2007, a second ASF epidemic wave caused by genotype II was registered, involving several European and extra-European countries, including Italy in 2022. The present paper aims to provide the state of the art of ASF in Italy, describing the course of ASF in wild boars and domestic pigs as an example of multiple concurring different scenarios. Sardinia is coping with the last phase of the eradication of the disease by applying the exit strategy. Conversely, four clusters of infection located in North, Central, and South Italy are still ongoing. The unique and complex Italian experience in ASF-controlling may be useful to increase know-how on the efficacy of strategies and measures, as well as issues that could be further improved. Full article

(This article belongs to the Special Issue African Swine Fever Virus Transmission and Control: The Role of Wild and Domestic Suids)

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