African Swine Fever Virus Infection

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

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 92902

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Animal and Plant Health Agency (APHA-Weybridge), Pathology Department (Building 57), Woodham Lane, New Haw, Addlestone, KT15 3NB, UK
Interests: veterinary medicine; veterinary pathology; pathogenesis and immunology of infectious diseases; African swine fever
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Dear Colleagues,

Without any doubt, African swine fever (ASF) constitutes the biggest global problem the swine industry has ever faced. Since ASF appeared in Georgia in 2007 as a result of the transcontinental spread of genotype II ASFV isolates originally from Southeast Africa, the disease has spread like wild fire, first crossing Europe from East to West, and then jumping to Asia and reaching in 2018 the world’s largest pig producer, China. The disease has continued its unstoppable march, affecting several countries in Southeast Asia, until reaching in September 2019 the very doors of the Australian continent. This catastrophic scenario has forced to kill million pigs and has created a pessimistic outlook about the future of more than 500 million pigs, generating uncertainty that will last for years affecting international trade and markets.

The key role played by wild boar population in the spread and maintenance of ASF has opened a new scenario in which, along with the protection of domestic pigs, the control of the disease by vaccination in wild boar has been pointed as critical for the future outcome of the epidemic. So far, it has been assumed that ASFV infection in wild boar has a similar course as in domestic pigs. However, there are important gaps of knowledge regarding the pathogenesis and immunological mechanisms of ASF specifically in wild boar, so that not only biological differences with domestic pigs require to be identified, but also additional differences between experimental and natural ASFV infection in wild boar should be assessed.

Although over the last years some breakthroughs have been achieved, so far any attempt to develop a commercial vaccine against ASFV has failed due to the complexity of the causative agent, the Africa swine fever virus (ASFV). The precise nature of the protective responses has not been determined and protective antigens have not yet been identified. In addition, mechanisms by which the virus modulates the host response to infection are poorly understood.

In this issue, we would like to focus on all aspects of ASF that provide an update of our current knowledge of the disease and may contribute to vaccine development. Topics of interest include (but are not limited to) transmission pathways, host–virus interactions, mechanisms of infection and viral spread, cell-virus interactions, disease dynamics, clinical aspects, pathology and standardization of pathological evaluation protocols, disease pathogenesis, factors responsible for virus virulence, virus persistence, vaccines, immune responses correlated with protection and how these can be activated, development and improvement of diagnostic techniques, new ASFV isolates discovery, epidemiology and antiviral drugs.

Dr. Pedro J. Sánchez-Cordón
Guest Editor

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Keywords

  • transmission pathways
  • host–virus interactions
  • mechanisms of infection and viral spread
  • cell-virus interactions
  • disease dynamics
  • clinical courses
  • pathology
  • disease pathogenesis
  • virus virulence
  • virus persistence
  • vaccines
  • immune response
  • diagnostic techniques
  • epidemiology
  • antiviral drugs

Published Papers (21 papers)

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23 pages, 4143 KiB  
Article
Evaluation of Lesions and Viral Antigen Distribution in Domestic Pigs Inoculated Intranasally with African Swine Fever Virus Ken05/Tk1 (Genotype X)
by Pedro J. Sánchez-Cordón, Tobias Floyd, Daniel Hicks, Helen R. Crooke, Stephen McCleary, Ronan R. McCarthy, Rebecca Strong, Linda K. Dixon, Aleksija Neimanis, Emil Wikström-Lassa, Dolores Gavier-Widén and Alejandro Núñez
Pathogens 2021, 10(6), 768; https://doi.org/10.3390/pathogens10060768 - 18 Jun 2021
Cited by 11 | Viewed by 3438
Abstract
The understanding of the pathogenic mechanisms and the clinicopathological forms caused by currently circulating African swine fever virus (ASFV) isolates is incomplete. So far, most of the studies have been focused on isolates classified within genotypes I and II, the only genotypes that [...] Read more.
The understanding of the pathogenic mechanisms and the clinicopathological forms caused by currently circulating African swine fever virus (ASFV) isolates is incomplete. So far, most of the studies have been focused on isolates classified within genotypes I and II, the only genotypes that have circulated outside of Africa. However, less is known about the clinical presentations and lesions induced by isolates belonging to the other twenty-two genotypes. Therefore, the early clinicopathological identification of disease outbreaks caused by isolates belonging to, as yet, not well-characterised ASFV genotypes may be compromised, which might cause a delay in the implementation of control measures to halt the virus spread. To improve the pathological characterisation of disease caused by diverse isolates, we have refined the macroscopic and histopathological evaluation protocols to standardise the scoring of lesions. Domestic pigs were inoculated intranasally with different doses (high, medium and low) of ASFV isolate Ken05/Tk1 (genotype X). To complement previous studies, the distribution and severity of macroscopic and histopathological lesions, along with the amount and distribution of viral antigen in tissues, were characterised by applying the new scoring protocols. The intranasal inoculation of domestic pigs with high doses of the Ken05/Tk1 isolate induced acute forms of ASF in most of the animals. Inoculation with medium doses mainly induced acute forms of disease. A less severe but longer clinical course, typical of subacute forms, characterised by the presence of more widespread and severe haemorrhages and oedema, was observed in one pig inoculated with the medium dose. The severity of vascular lesions (haemorrhages and oedema) induced by high and medium doses was not associated with the amount of virus antigen detected in tissues, therefore these might be attributed to indirect mechanisms not evaluated in the present study. The absence of clinical signs, lesions and detectable levels of virus genome or antigen in blood from the animals inoculated with the lowest dose ruled out the existence of possible asymptomatic carriers or persistently infected pigs, at least for the 21 days period of the study. The results corroborate the moderate virulence of the Ken05/Tk1 isolate, as well as its capacity to induce both the acute and, occasionally, subacute forms of ASF when high and medium doses were administered intranasally. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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12 pages, 2226 KiB  
Article
Development of a Blocking Enzyme-Linked Immunosorbent Assay for Detection of Antibodies against African Swine Fever Virus
by Fangfeng Yuan, Vlad Petrovan, Luis Gabriel Gimenez-Lirola, Jeffrey J. Zimmerman, Raymond R. R. Rowland and Ying Fang
Pathogens 2021, 10(6), 760; https://doi.org/10.3390/pathogens10060760 - 17 Jun 2021
Cited by 28 | Viewed by 3811
Abstract
The incursion of African swine fever virus (ASFV) into Eurasia presents a threat to the world’s swine industry. Highly sensitive and specific diagnostic assays are urgently needed for rapid detection during an outbreak, post-outbreak investigation, and disease surveillance. In this study, a highly [...] Read more.
The incursion of African swine fever virus (ASFV) into Eurasia presents a threat to the world’s swine industry. Highly sensitive and specific diagnostic assays are urgently needed for rapid detection during an outbreak, post-outbreak investigation, and disease surveillance. In this study, a highly specific and repeatable blocking ELISA (bELISA) was developed using a recombinant p30 protein as the antigen combined with biotinylated mAb against p30 as the detection antibody. Initial test validation included sera from 810 uninfected animals and 106 animals experimentally inoculated with ASFV or recombinant alphavirus/adenovirus expressing p30. Receiver operating characteristic (ROC) analysis of the data calculated an optimal percentage of inhibition (PI) cutoff value of 45.92%, giving a diagnostic sensitivity of 98.11% and diagnostic specificity of 99.42%. The coefficient of variation of an internal quality control serum was 6.81% for between runs, 6.71% for within run, and 6.14% for within plate. A time course study of infected pigs showed that bELISA was able to detect seroconversion as early as 7 days post-inoculation. Taken together, these results demonstrate that bELISA can be used as an alternative serological test for detecting ASFV infection. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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13 pages, 1694 KiB  
Article
The Role of Interleukine-10 and Interferon-γ as Potential Markers of the Evolution of African Swine Fever Virus Infection in Wild Boar
by Sandra Barroso-Arévalo, Jose A. Barasona, Estefanía Cadenas-Fernández and Jose M. Sánchez-Vizcaíno
Pathogens 2021, 10(6), 757; https://doi.org/10.3390/pathogens10060757 - 15 Jun 2021
Cited by 9 | Viewed by 2698
Abstract
African swine fever virus (ASFv) is one of the most challenging pathogens to affect both domestic and wild pigs. The disease has now spread to Europe and Asia, causing great damage to the pig industry. Although no commercial vaccine with which to control [...] Read more.
African swine fever virus (ASFv) is one of the most challenging pathogens to affect both domestic and wild pigs. The disease has now spread to Europe and Asia, causing great damage to the pig industry. Although no commercial vaccine with which to control the disease is, as yet, available, some potential vaccine candidates have shown good results in terms of protection. However, little is known about the host immune mechanisms underlying that protection, especially in wild boar, which is the main reservoir of the disease in Europe. Here, we study the role played by two cytokines (IL-10 and IFN-γ) in wild boar orally inoculated with the attenuated vaccine candidate Lv17/WB/Rie1 and challenged with a virulent ASFv genotype II isolate. A group of naïve wild boar challenged with the latter isolate was also established as a control group. Our results showed that both cytokines play a key role in protecting the host against the challenge virus. While high levels of IL-10 in serum may trigger an immune system malfunctioning in challenged animals, the provision of stable levels of this cytokine over time may help to control the disease. This, together with high and timely induction of IFN-γ by the vaccine candidate, could help protect animals from fatal outcomes. Further studies should be conducted in order to support these preliminary results and confirm the role of these two cytokines as potential markers of the evolution of ASFV infection. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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15 pages, 2219 KiB  
Article
African Swine Fever Laboratory Diagnosis—Lessons Learned from Recent Animal Trials
by Jutta Pikalo, Paul Deutschmann, Melina Fischer, Hanna Roszyk, Martin Beer and Sandra Blome
Pathogens 2021, 10(2), 177; https://doi.org/10.3390/pathogens10020177 - 6 Feb 2021
Cited by 20 | Viewed by 4042
Abstract
African swine fever virus (ASFV) causes a hemorrhagic disease in pigs with high socio-economic consequences. To lower the impact of disease incursions, early detection is crucial. In the context of experimental animal trials, we evaluated diagnostic workflows for a high sample throughput in [...] Read more.
African swine fever virus (ASFV) causes a hemorrhagic disease in pigs with high socio-economic consequences. To lower the impact of disease incursions, early detection is crucial. In the context of experimental animal trials, we evaluated diagnostic workflows for a high sample throughput in active surveillance, alternative sample matrices for passive surveillance, and lateral flow devices (LFD) for rapid testing. We could demonstrate that EDTA blood is significantly better suited for early ASFV detection than serum. Tissues recommended by the respective diagnostic manuals were in general comparable in their performance, with spleen samples giving best results. Superficial lymph nodes, ear punches, and different blood swabs were also evaluated as potential alternatives. In summary, all matrices yielded positive results at the peak of clinical signs and could be fit for purpose in passive surveillance. However, weaknesses were discovered for some matrices when it comes to the early phase of infection or recovery. The antigen LFD showed variable results with best performance in the clinical phase. The antibody LFD was quite comparable with ELISA systems. Concluding, alternative approaches are feasible but have to be embedded in control strategies selecting test methods and sample materials following a “fit-for-purpose” approach. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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11 pages, 2425 KiB  
Article
Analysis of Risk Factors for African Swine Fever in Lombardy to Identify Pig Holdings and Areas Most at Risk of Introduction in Order to Plan Preventive Measures
by Silvia Bellini, Alessandra Scaburri, Marco Tironi and Stefania Calò
Pathogens 2020, 9(12), 1077; https://doi.org/10.3390/pathogens9121077 - 21 Dec 2020
Cited by 4 | Viewed by 1980
Abstract
In 2019, the area of the European Union (EU) affected by African swine fever (ASF) expanded progressively in a southwestern direction from Baltic and eastern countries. The disease can severely affect and disrupt regional and international trade of pigs and pork products with [...] Read more.
In 2019, the area of the European Union (EU) affected by African swine fever (ASF) expanded progressively in a southwestern direction from Baltic and eastern countries. The disease can severely affect and disrupt regional and international trade of pigs and pork products with serious socioeconomic damages to the pig industry. Lombardy is one of the most important European pig producers and the introduction of ASF into the pig population could adversely affect the entire sector. A study was carried out to identify the farms and territories in the region most at risk of ASF introduction to plan preventive measures. The pig holdings were identified through a descriptive analysis of pig movements and Social Network Analysis (SNA), while, for the identification of the most exposed municipalities, an assessment of risk factors was carried out using the ranking of summed scores attributed to the Z-score. From the analysis, it was found that 109 municipalities and 297 pig holdings of the region were potentially more at risk, and these holdings were selected for target surveillance. This information was provided to veterinary authority to target surveillance in pig farms, in order to early detect a possible incursion of ASF and prevent its spread. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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12 pages, 37488 KiB  
Article
Stability of African Swine Fever Virus in Soil and Options to Mitigate the Potential Transmission Risk
by Jolene Carlson, Melina Fischer, Laura Zani, Michael Eschbaumer, Walter Fuchs, Thomas Mettenleiter, Martin Beer and Sandra Blome
Pathogens 2020, 9(11), 977; https://doi.org/10.3390/pathogens9110977 - 23 Nov 2020
Cited by 37 | Viewed by 4410
Abstract
Understanding African swine fever virus (ASFV) transmission is essential for strategies to minimize virus spread during an outbreak. ASFV can survive for extended time periods in animal products, carcasses, and the environment. While the ASFV genome was found in environments around infected farms, [...] Read more.
Understanding African swine fever virus (ASFV) transmission is essential for strategies to minimize virus spread during an outbreak. ASFV can survive for extended time periods in animal products, carcasses, and the environment. While the ASFV genome was found in environments around infected farms, data on the virus survival in soil are scarce. We investigated different soil matrices spiked with ASFV-positive blood from infected wild boar to see if ASFV can remain infectious in the soil beneath infected carcasses. As expected, ASFV genome detection was possible over the entire sampling period. Soil pH, structure, and ambient temperature played a role in the stability of infectious ASFV. Infectious ASFV was demonstrated in specimens originating from sterile sand for at least three weeks, from beach sand for up to two weeks, from yard soil for one week, and from swamp soil for three days. The virus was not recovered from two acidic forest soils. All risk mitigation experiments with citric acid or calcium hydroxide resulted in complete inactivation. In conclusion, the stability of infectious ASFV is very low in acidic forest soils but rather high in sandy soils. However, given the high variability, treatment of carcass collection points with disinfectants should be considered. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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10 pages, 898 KiB  
Article
Effectiveness of Chemical Compounds Used against African Swine Fever Virus in Commercial Available Disinfectants
by Małgorzata Juszkiewicz, Marek Walczak, Natalia Mazur-Panasiuk and Grzegorz Woźniakowski
Pathogens 2020, 9(11), 878; https://doi.org/10.3390/pathogens9110878 - 24 Oct 2020
Cited by 33 | Viewed by 6934
Abstract
African swine fever (ASF) causes huge economic losses and is one of most dangerous diseases of pigs. The disease is known for almost 100 years, an effective vaccine or treatment is still unavailable, only proper biosecurity measures, including disinfection, are being applied, in [...] Read more.
African swine fever (ASF) causes huge economic losses and is one of most dangerous diseases of pigs. The disease is known for almost 100 years, an effective vaccine or treatment is still unavailable, only proper biosecurity measures, including disinfection, are being applied, in order to prevent disease outbreaks. Eight active substances, i.e., formaldehyde, sodium hypochlorite, caustic soda, glutaraldehyde, phenol, benzalkonium chloride, potassium peroxymonosulfate and acetic acid, were tested, in order to confirm their effectiveness against African swine fever virus (ASFV). This specific selection was done based on the World Organisation for Animal Health (OIE)’s recommendation and previous disinfectant studies on surfaces. The result of our study shows that most of them inactivate the virus, in recommended concentrations. In order to reduce the cytotoxicity of the four substances, Microspin S-400 HR columns were applied, therefore making it possible to demonstrate four logarithms virus titer reduction. Sodium hypochlorite, glutaraldehyde, caustic soda and potassium peroxymonosulfate showed the best ASFV inactivation rates, achieving titer reductions over 5 logs. Despite microfiltration, the virucidal activity of formaldehyde was not assessable, due to its high cytotoxicity. Our results showed that cleaning is particularly important, because removal of the soiling provides improved effectiveness of the tested chemical compounds. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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16 pages, 3479 KiB  
Article
Clinical Course and Gross Pathological Findings in Wild Boar Infected with a Highly Virulent Strain of African Swine Fever Virus Genotype II
by Antonio Rodríguez-Bertos, Estefanía Cadenas-Fernández, Agustín Rebollada-Merino, Néstor Porras-González, Francisco J. Mayoral-Alegre, Lucía Barreno, Aleksandra Kosowska, Irene Tomé-Sánchez, José A. Barasona and José M. Sánchez-Vizcaíno
Pathogens 2020, 9(9), 688; https://doi.org/10.3390/pathogens9090688 - 22 Aug 2020
Cited by 16 | Viewed by 5144
Abstract
African swine fever (ASF) is a notifiable disease that in recent years has spread remarkably in Europe and Asia. Eurasian wild boar (Sus scrofa) plays a key role in the maintenance and spread of the pathogen. Here we examined gross pathology [...] Read more.
African swine fever (ASF) is a notifiable disease that in recent years has spread remarkably in Europe and Asia. Eurasian wild boar (Sus scrofa) plays a key role in the maintenance and spread of the pathogen. Here we examined gross pathology of infection in wild boar with a highly virulent, hemadsorbing genotype II ASF virus (ASFV) strain. To this end, six wild boars were intramuscularly inoculated with the 10 HAD50 Arm07 ASFV strain, and 11 wild boars were allowed to come into direct contact with the inoculated animals. No animals survived the infection. Clinical course, gross pathological findings and viral genome quantification by PCR in tissues did not differ between intramuscularly inoculated or contact-infected animals. Postmortem analysis showed enlargement of liver and spleen; serosanguinous effusion in body cavities; and multiple hemorrhages in lungs, endocardium, brain, kidneys, urinary bladder, pancreas, and alimentary system. These results provide detailed insights into the gross pathology of wild boar infected with a highly virulent genotype II ASFV strain. From a didactic point of view, this detailed clinical course and macroscopic description may be essential for early postmortem detection of outbreaks in wild boar in the field and contribute to disease surveillance and prevention efforts. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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23 pages, 10018 KiB  
Article
Comparative Pathology of Domestic Pigs and Wild Boar Infected with the Moderately Virulent African Swine Fever Virus Strain “Estonia 2014”
by Julia Sehl, Jutta Pikalo, Alexander Schäfer, Kati Franzke, Katrin Pannhorst, Ahmed Elnagar, Ulrike Blohm, Sandra Blome and Angele Breithaupt
Pathogens 2020, 9(8), 662; https://doi.org/10.3390/pathogens9080662 - 16 Aug 2020
Cited by 30 | Viewed by 4233
Abstract
Endemically infected European wild boar are considered a major reservoir of African swine fever virus in Europe. While high lethality was observed in the majority of field cases, strains of moderate virulence occurred in the Baltic States. One of these, “Estonia 2014”, led [...] Read more.
Endemically infected European wild boar are considered a major reservoir of African swine fever virus in Europe. While high lethality was observed in the majority of field cases, strains of moderate virulence occurred in the Baltic States. One of these, “Estonia 2014”, led to a higher number of clinically healthy, antibody-positive animals in the hunting bag of North-Eastern Estonia. Experimental characterization showed high virulence in wild boar but moderate virulence in domestic pigs. Putative pathogenic differences between wild boar and domestic pigs are unresolved and comparative pathological studies are limited. We here report on a kinetic experiment in both subspecies. Three animals each were euthanized at 4, 7, and 10 days post infection (dpi). Clinical data confirmed higher virulence in wild boar although macroscopy and viral genome load in blood and tissues were comparable in both subspecies. The percentage of viral antigen positive myeloid cells tested by flow cytometry did not differ significantly in most tissues. Only immunohistochemistry revealed consistently higher viral antigen loads in wild boar tissues in particular 7 dpi, whereas domestic pigs already eliminated the virus. The moderate virulence in domestic pigs could be explained by a more effective viral clearance. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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13 pages, 1025 KiB  
Article
Molecular Characterization of African Swine Fever Virus Isolates in Estonia in 2014–2019
by Annika Vilem, Imbi Nurmoja, Tarmo Niine, Taavi Riit, Raquel Nieto, Arvo Viltrop and Carmina Gallardo
Pathogens 2020, 9(7), 582; https://doi.org/10.3390/pathogens9070582 - 17 Jul 2020
Cited by 27 | Viewed by 3702
Abstract
After the extensive spread of the African swine fever virus (ASFV) genotype II in Eastern Europe, the first case of African swine fever (ASF) in Estonia was diagnosed in September 2014. By the end of 2019, 3971 ASFV-positive wild boars were found, and [...] Read more.
After the extensive spread of the African swine fever virus (ASFV) genotype II in Eastern Europe, the first case of African swine fever (ASF) in Estonia was diagnosed in September 2014. By the end of 2019, 3971 ASFV-positive wild boars were found, and 27 domestic pig outbreaks were reported. A selection of ASFV isolates from wild boar and domestic pigs (during the period of September 2014–2019) was molecularly characterized using standardized genotyping procedures. One of the proven markers to characterize this virus is the central variable region (CVR) within the B602L gene. In summer 2015, a new ASFV genotype II CVR variant 2 (GII-CVR2) was confirmed in Estonia. The results suggest that the GII-CVR2 variant was only confirmed in wild boar from a limited area in southern Estonia in 2015 and 2016. In addition to GII-CVR2, a single nucleotide polymorphism (SNP) that resulted in amino acid change was identified within the genotype II CVR variant 1 (GII-CVR1). The GII-CVR1/SNP1 strain was isolated in Estonia in November 2016. Additional GII-CVR1/SNP1 cases were confirmed in two neighbouring counties, as well as in one outbreak farm in June 2017. Based on the available data, no GII-CVR2 and GII-CVR1/SNP1 have been reported by other affected European countries. The spread of variant strains in Estonia has been limited over time, and restricted to a relatively small area. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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23 pages, 1913 KiB  
Article
Risk Assessment of African Swine Fever Virus Exposure to Sus scrofa in Japan Via Pork Products Brought in Air Passengers’ Luggage
by Satoshi Ito, Jaime Bosch, Cristina Jurado, José Manuel Sánchez-Vizcaíno and Norikazu Isoda
Pathogens 2020, 9(4), 302; https://doi.org/10.3390/pathogens9040302 - 20 Apr 2020
Cited by 11 | Viewed by 3887
Abstract
In recent years, African swine fever (ASF) has become prevalent in many areas, including Asia. The repeated detection of the ASF virus (ASFV) genome in pork products brought in air passenger’s luggage (PPAP) was also reported from Japanese airports. In the present study, [...] Read more.
In recent years, African swine fever (ASF) has become prevalent in many areas, including Asia. The repeated detection of the ASF virus (ASFV) genome in pork products brought in air passenger’s luggage (PPAP) was also reported from Japanese airports. In the present study, the risk of ASFV exposure to susceptible hosts in Japan via three different pathways was assessed. Two quantitative stochastic risk assessment models were built to estimate the annual probability of ASFV exposure to domestic pigs, which could be attributed to foreign job trainees or foreign tourists. A semi-quantitative stochastic model was built to assess the risk of ASFV exposure to wild boar caused by foreign tourists. The overall mean annual probability of ASFV exposure to domestic pigs via PPAP carried by foreign job trainees was 0.169 [95% confidence interval (CI): 0.000–0.600], whereas that by foreign tourists was 0.050 [95% CI: 0.000–0.214], corresponding to approximately one introduction every 5.9 and 20 years, respectively. The risk of ASFV exposure to domestic pigs was dispersed over the country, whereas that of wild boar was generally higher in the western part of Japan, indicating that the characteristics of the potential ASF risk in each prefecture were varied. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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11 pages, 3111 KiB  
Article
Analysis of the Clinical Course of Experimental Infection with Highly Pathogenic African Swine Fever Strain, Isolated from an Outbreak in Poland. Aspects Related to the Disease Suspicion at the Farm Level
by Marek Walczak, Jacek Żmudzki, Natalia Mazur-Panasiuk, Małgorzata Juszkiewicz and Grzegorz Woźniakowski
Pathogens 2020, 9(3), 237; https://doi.org/10.3390/pathogens9030237 - 22 Mar 2020
Cited by 27 | Viewed by 4695
Abstract
This paper was aimed to characterize clinical signs and pathomorphological lesions in twenty-two pigs, infected intranasally by different doses of African swine fever virus (Pol18_28298_O111), isolated during the outbreak in a pig farm that occurred in Eastern Poland throughout 2018. This article also [...] Read more.
This paper was aimed to characterize clinical signs and pathomorphological lesions in twenty-two pigs, infected intranasally by different doses of African swine fever virus (Pol18_28298_O111), isolated during the outbreak in a pig farm that occurred in Eastern Poland throughout 2018. This article also attempts to indicate risk, related to virus load and shedding, and present possible difficulties with proper disease recognition at the farm level. The results revealed that even a very low dose (5 HAU) may initiate the infection. Various forms of the disease (acute, subacute, and chronic), mainly with prodromal clinical signs like fever, apathy, and reduced feed intake were observed. The most frequently observed lesions (82%) were: hyperemia and enlargement of lymph nodes and splenomegaly. The minimal incubation period was estimated at five days post-infection (dpi). Mortality ranged from 80–100%. Two pigs survived the infection. Some viremic animals presented delayed fever. In some cases, the fever was not detectable. Shortly after viremia, the virus was secreted ion the urine, feces, and saliva. The highest levels of virus were found in the internal organs and blood; however in the case of one pig (chronic form), viral DNA was not detected in the spleen, liver, bone marrow, and brain. Veterinary diagnosis may be difficult, and the final results should always be based on laboratory investigations. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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18 pages, 2526 KiB  
Article
Comparison of Macrophage Responses to African Swine Fever Viruses Reveals that the NH/P68 Strain is Associated with Enhanced Sensitivity to Type I IFN and Cytokine Responses from Classically Activated Macrophages
by Giulia Franzoni, Elisabetta Razzuoli, Silvia Dei Giudici, Tania Carta, Grazia Galleri, Susanna Zinellu, Mauro Ledda, Pierpaolo Angioi, Paola Modesto, Simon P. Graham and Annalisa Oggiano
Pathogens 2020, 9(3), 209; https://doi.org/10.3390/pathogens9030209 - 12 Mar 2020
Cited by 28 | Viewed by 4472
Abstract
African swine fever (ASF) poses a severe threat to the global pig industry for which currently there is no available vaccine. The aetiological ASF virus (ASFV) has a predilection for cells of the myeloid lineage, however little is known about its interaction with [...] Read more.
African swine fever (ASF) poses a severe threat to the global pig industry for which currently there is no available vaccine. The aetiological ASF virus (ASFV) has a predilection for cells of the myeloid lineage, however little is known about its interaction with polarised macrophages. This study focused on the in vitro interactions of porcine monocyte-derived un-activated (moMΦ), classically (moM1), alternatively (moM2), and IFN-α-activated macrophages with two genotype I ASFV strains: virulent 22653/14 and attenuated NH/P68. At a high multiplicity of infection, NH/P68, but not 22653/14, presented a reduced ability to infect moM1 and IFN−α-activated moMΦ compared to moMΦ. IFN-α activation resulted in a dose-dependent reduction in the proportion of ASFV-infected cells. Both strains replicated efficiently in all the subsets. While higher levels of IL-1α, IL-1β, and IL-18 were secreted by NH/P68-infected moM1 compared to 22653/14, both strains negatively affected moMΦ ability to release IL-6, IL-12, TNF-α in response to classical activation or stimulation with a TLR2 agonist. Our results suggest that ASFV 22653/14 covertly replicates in macrophages, compromising the development of effective immune responses. Attenuated NH/P68 has partially lost these mechanisms, which may enhance immune surveillance. A better understating of these mechanisms should aid the rational design of live attenuated ASFV vaccines. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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14 pages, 2191 KiB  
Article
Adenovirus-vectored African Swine Fever Virus Antigens Cocktail Is Not Protective against Virulent Arm07 Isolate in Eurasian Wild Boar
by Estefanía Cadenas-Fernández, Jose M. Sánchez-Vizcaíno, Aleksandra Kosowska, Belén Rivera, Francisco Mayoral-Alegre, Antonio Rodríguez-Bertos, Jianxiu Yao, Jocelyn Bray, Shehnaz Lokhandwala, Waithaka Mwangi and Jose A. Barasona
Pathogens 2020, 9(3), 171; https://doi.org/10.3390/pathogens9030171 - 28 Feb 2020
Cited by 35 | Viewed by 4156
Abstract
African swine fever (ASF) is a viral disease of domestic and wild suids for which there is currently no vaccine or treatment available. The recent spread of ASF virus (ASFV) through Europe and Asia is causing enormous economic and animal losses. Unfortunately, the [...] Read more.
African swine fever (ASF) is a viral disease of domestic and wild suids for which there is currently no vaccine or treatment available. The recent spread of ASF virus (ASFV) through Europe and Asia is causing enormous economic and animal losses. Unfortunately, the measures taken so far are insufficient and an effective vaccine against ASFV needs to be urgently developed. We hypothesized that immunization with a cocktail of thirty-five rationally selected antigens would improve the protective efficacy of subunit vaccine prototypes given that the combination of fewer immunogenic antigens (between 2 and 22) has failed to elicit protective efficacy. To this end, immunogenicity and efficacy of thirty-five adenovirus-vectored ASFV antigens were evaluated in wild boar. The treated animals were divided into different groups to test the use of BioMize adjuvant and different inoculation strategies. Forty-eight days after priming, the nine treated and two control wild boar were challenged with the virulent ASFV Arm07 isolate. All animals showed clinical signs and pathological findings consistent with ASF. This lack of protection is in line with other studies with subunit vaccine prototypes, demonstrating that there is still much room for improvement to obtain an effective subunit ASFV vaccine. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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6 pages, 252 KiB  
Communication
No Experimental Evidence of Co-Feeding Transmission of African Swine Fever Virus between Ornithodoros Soft Ticks
by Rémi Pereira De Oliveira, Evelyne Hutet, Maxime Duhayon, Frédéric Paboeuf, Marie-Frédérique Le Potier and Laurence Vial
Pathogens 2020, 9(3), 168; https://doi.org/10.3390/pathogens9030168 - 28 Feb 2020
Cited by 2 | Viewed by 2676
Abstract
Ornithodoros soft ticks are the only known vector and reservoir of the African swine fever virus, a major lethal infectious disease of Suidae. The co-feeding event for virus transmission and maintenance among soft tick populations has been poorly documented. We infected Ornithodoros [...] Read more.
Ornithodoros soft ticks are the only known vector and reservoir of the African swine fever virus, a major lethal infectious disease of Suidae. The co-feeding event for virus transmission and maintenance among soft tick populations has been poorly documented. We infected Ornithodoros moubata, a known tick vector in Africa, with an African swine fever virus strain originated in Africa, to test its ability to infect O. moubata through co-feeding on domestic pigs. In our experimental conditions, tick-to-tick virus transmission through co-feeding failed, although pigs became infected through the infectious tick bite. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
18 pages, 2738 KiB  
Article
Drivers, Risk Factors and Dynamics of African Swine Fever Outbreaks, Southern Highlands, Tanzania
by Folorunso O. Fasina, Henry Kissinga, Fredy Mlowe, Samora Mshang’a, Benedict Matogo, Abnery Mrema, Adam Mhagama, Selemani Makungu, Niwael Mtui-Malamsha, Raphael Sallu, Gerald Misinzo, Bishop Magidanga, Fredrick Kivaria, Charles Bebay, Solomon Nong’ona, Fred Kafeero and Hezron Nonga
Pathogens 2020, 9(3), 155; https://doi.org/10.3390/pathogens9030155 - 25 Feb 2020
Cited by 23 | Viewed by 5256
Abstract
African swine fever remains an important pig disease globally in view of its rapid spread, economic impacts and food implications, with no option of vaccination or treatment. The Southern Highlands zone of Tanzania, an important pig-producing hub in East Africa, is endemic with [...] Read more.
African swine fever remains an important pig disease globally in view of its rapid spread, economic impacts and food implications, with no option of vaccination or treatment. The Southern Highlands zone of Tanzania, an important pig-producing hub in East Africa, is endemic with African swine fever (ASF). From approximately the year 2010, the recurrence of outbreaks has been observed and it has now become a predictable pattern. We conducted exploratory participatory epidemiology and participatory disease surveillance in the Southern Highlands to understand the pig sector and the drivers and facilitators of infections, risk factors and dynamics of ASF in this important pig-producing area. Pigs continue to play a major role in rural livelihoods in the Southern Highlands and pork is a major animal protein source. Outbreaks of diseases, particularly ASF, have continued to militate against the scaling up of pig operations in the Southern Highlands. Intra- and inter-district and trans-border transnational outbreaks of ASF, the most common disease in the Southern Highlands, continue to occur. Trade and marketing systems, management systems, and lack of biosecurity, as well as anthropogenic (human) issues, animals and fomites, were identified as risk factors and facilitators of ASF infection. Changes in human behavior and communication in trade and marketing systems in the value chain, biosecurity and pig management practices are warranted. Relevant training must be implemented alongside the launch of the national ASF control strategy for Tanzania, which already established a roadmap for combating ASF in Tanzania. The high-risk points (slaughter slabs, border areas, and farms with poor biosecurity) and high-risk period (November–March) along the pig value chain must be targeted as critical control points for interventions in order to reduce the burden of infection. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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Review

Jump to: Research, Other

13 pages, 4862 KiB  
Review
African Swine Fever in Cameroon: A Review
by Ebanja Joseph Ebwanga, Stephen Mbigha Ghogomu and Jan Paeshuyse
Pathogens 2021, 10(4), 421; https://doi.org/10.3390/pathogens10040421 - 1 Apr 2021
Cited by 9 | Viewed by 3228
Abstract
African swine fever (ASF) is a hemorrhagic contagious porcine disease caused by the African swine fever virus. The disease poses enormous problems to the pork industry with pig mortality ranging from 30% to 100%, depending on the virulence of the virus circulating. Cameroon, [...] Read more.
African swine fever (ASF) is a hemorrhagic contagious porcine disease caused by the African swine fever virus. The disease poses enormous problems to the pork industry with pig mortality ranging from 30% to 100%, depending on the virulence of the virus circulating. Cameroon, situated in Central Africa is one of the countries in which the African swine fever virus (ASFV) has been endemic since its first outbreak in 1982. The disease is a major problem to the pig industry causing huge economic losses. A clear and concise review on ASF in Cameroon relating to the entry and current genotype of the virus, epidemiology, pathogenesis and economic impact is lacking. A thorough literature search revealed: (1) The virus entered the country in 1982 and caused the death of 80% of the pigs. (2) All isolates belong to serogroup I and only Genotype I is circulating in Cameroon principally in the domestic cycle as there are neither soft ticks nor warthog in the pig production regions sampled. (3) 70% of the pig farmers are involved in the traditional system of production with local and hybrid breeds of pigs with minimal input. (4) The country is endemic to the virus with huge economic losses. (5) So far, very little research has been effected on ASFV in Cameroon. This review gives a detailed overview of the situation of African swine fever virus (ASFV) in the country along with potential avenues for future research into ASFV in Cameroon. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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15 pages, 316 KiB  
Review
A Review of Risk Factors of African Swine Fever Incursion in Pig Farming within the European Union Scenario
by Silvia Bellini, Gabriele Casadei, Giorgia De Lorenzi and Marco Tamba
Pathogens 2021, 10(1), 84; https://doi.org/10.3390/pathogens10010084 - 19 Jan 2021
Cited by 42 | Viewed by 7297
Abstract
African swine fever (ASF) is a notifiable viral disease of pigs and wild boars that could lead to serious economic losses for the entire European pork industry. As no effective treatment or vaccination is available, disease prevention and control rely on strictly enforced [...] Read more.
African swine fever (ASF) is a notifiable viral disease of pigs and wild boars that could lead to serious economic losses for the entire European pork industry. As no effective treatment or vaccination is available, disease prevention and control rely on strictly enforced biosecurity measures tailored to the specific risk factors of ASF introduction within domestic pig populations. Here, we present a review addressing the risk factors associated with different European pig farming systems in the context of the actual epidemiological scenario. A list of keywords was combined into a Boolean query, “African swine fever” AND (“Risk factors” OR “Transmission” OR “Spread” OR “Pig farming” OR “Pigs” OR “Wild boars”); was run on 4 databases; and resulted in 52 documents of interest being reviewed. Based on our review, each farming system has its own peculiar risk factors: commercial farms, where best practices are already in place, may suffer from unintentional breaches in biosecurity, while backyard and outdoor farms may suffer from poor ASF awareness, sociocultural factors, and contact with wild boars. In the literature selected for our review, human-related activities and behaviours are presented as the main risks, but we also stress the need to implement biosecurity measures also tailored to risks factors that are specific for the different pig farming practices in the European Union (EU). Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
12 pages, 257 KiB  
Review
Protective Properties of Attenuated Strains of African Swine Fever Virus Belonging to Seroimmunotypes I–VIII
by Alexey D. Sereda, Vladimir M. Balyshev, Anna S. Kazakova, Almaz R. Imatdinov and Denis V. Kolbasov
Pathogens 2020, 9(4), 274; https://doi.org/10.3390/pathogens9040274 - 9 Apr 2020
Cited by 40 | Viewed by 3618
Abstract
This article summarizes the study results on the generation of attenuated strains of African swine fever virus (ASFV) of seroimmunotypes I–VIII and the creation of live vaccines for temporary protection of pigs during a period of epizootics in the surveillance zone (a zone [...] Read more.
This article summarizes the study results on the generation of attenuated strains of African swine fever virus (ASFV) of seroimmunotypes I–VIII and the creation of live vaccines for temporary protection of pigs during a period of epizootics in the surveillance zone (a zone adjacent to the area of outbreak). These studies were initiated at the Federal Research Center for Virology and Microbiology (FRCVM, formerly VNIIVViM) at the time of introduction of the pathogen to the Iberian Peninsula in the middle of the 20th century. The developed experimental vaccines against ASFV seroimmunotypes I–V provided protection against virulent strains of homologous seroimmunotypes by day 14 after vaccination, lasting at least four months. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)

Other

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18 pages, 1942 KiB  
Perspective
Assessment of Risk Factors of African Swine Fever in India: Perspectives on Future Outbreaks and Control Strategies
by Mousumi Bora, Durlav Prasad Bora, Mohan Manu, Nagendra Nath Barman, Lakshya Jyoti Dutta, Pesingi Pavan Kumar, Suvaneeth Poovathikkal, Kuralayanapalya Puttahonnappa Suresh and Ramadevi Nimmanapalli
Pathogens 2020, 9(12), 1044; https://doi.org/10.3390/pathogens9121044 - 12 Dec 2020
Cited by 19 | Viewed by 6147
Abstract
African swine fever (ASF) is one of the most important transboundary diseases of pigs. ASF has been identified in India for the first time in domestic pigs from outbreaks reported in two of the northeastern states, Arunachal Pradesh and Assam in 2020. A [...] Read more.
African swine fever (ASF) is one of the most important transboundary diseases of pigs. ASF has been identified in India for the first time in domestic pigs from outbreaks reported in two of the northeastern states, Arunachal Pradesh and Assam in 2020. A total of 11 ASF outbreaks in different regions killed over 3700 pigs and devastated the economy of small-scale livestock owners of both the states. Considering the first outbreak of ASF in India, a generic risk assessment framework was determined to identify potential risk factors that might favor future emergence of the disease. Based on the Indian scenario, we considered population density of host, farming practice, availability of biological vectors and wildlife reservoirs, epidemiological cycles, and international trade to analyze the possibility of future outbreaks of ASF and chances of establishment of endemism. On critical analysis of the identified risk factors associated with ASFV transmission, we observed that the risk factors are well preserved in the Indian geography and might participate in future outbreaks, further disseminating the disease to nearby countries. Since no vaccine is currently available against ASF, the domestic and the wild pigs (wild boars and the endangered pygmy hogs native to India) of this region are under constant threat of infection. For the near future, this region will have to continue to rely on the implementation of preventive measures to avoid the devastating losses that outbreaks can cause. The various adaptive control strategies to minimize the risks associated with the transmission of ASF, keeping our views to Indian settings, have been described. The risk-analysis framework presented in the study will give a further understanding of the dynamics of disease transmission and will help to design control strategies and corresponding measures to minimize the catastrophic consequences of ASF disease. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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10 pages, 1322 KiB  
Brief Report
Modulation of Type I Interferon System by African Swine Fever Virus
by Elisabetta Razzuoli, Giulia Franzoni, Tania Carta, Susanna Zinellu, Massimo Amadori, Paola Modesto and Annalisa Oggiano
Pathogens 2020, 9(5), 361; https://doi.org/10.3390/pathogens9050361 - 9 May 2020
Cited by 29 | Viewed by 4287
Abstract
African Swine Fever Virus (ASFV) has tropism for macrophages, which seems to play a crucial role in disease pathogenesis and viral dissemination. Previous studies showed that ASFV developed mechanisms to evade type I interferon (IFN) responses. Hence, we analyzed the ability of ASFV [...] Read more.
African Swine Fever Virus (ASFV) has tropism for macrophages, which seems to play a crucial role in disease pathogenesis and viral dissemination. Previous studies showed that ASFV developed mechanisms to evade type I interferon (IFN) responses. Hence, we analyzed the ability of ASFV strains of diverse virulence to modulate IFN-β and IFN-α responses. Porcine monocyte-derived macrophages un-activated (moMΦ) or activated with IFN-α (moMΦ + FN-α) were infected with virulent (22653/14) or attenuated (NH/P68) ASFV strains, and expressions of IFN-β and of 17 IFN-α subtypes genes were monitored over time. ASFV strains of diverse virulence induced different panels of IFN genes: infection of moMΦ with either strains caused statistically significant up-regulation of IFN-α3, -α7/11, whereas only attenuated NH/P68 determined statistically significant up-regulation of IFN-α10, -α12, -α13, -α15, -α17, and IFN-β. Infection of activated moMΦ with either strains resulted in up-regulation of IFN-β and many IFN-α subtypes, but statistical significance was found only for IFN-α1, -α10, -α15, -α16, -α17 in response to NH/P68-infection only. These data revealed differences in type I IFNs expression patterns, with differences between strains of diverse virulence. In addition, virulent 22653/14 ASFV seems to have developed mechanisms to suppress the induction of several type I IFN genes. Full article
(This article belongs to the Special Issue African Swine Fever Virus Infection)
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