Special Issue "African Swine Fever Virus Infection"

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

Deadline for manuscript submissions: 31 July 2020.

Special Issue Editor

Dr. Pedro J. Sánchez-Cordón
Website
Guest Editor
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

Special Issue Information

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

Manuscript Submission Information

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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 (8 papers)

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Research

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Open AccessArticle
Risk Assessment of African Swine Fever Virus Exposure to Sus scrofa in Japan Via Pork Products Brought in Air Passengers’ Luggage
Pathogens 2020, 9(4), 302; https://doi.org/10.3390/pathogens9040302 - 20 Apr 2020
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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Open AccessArticle
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
Pathogens 2020, 9(3), 237; https://doi.org/10.3390/pathogens9030237 - 22 Mar 2020
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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Open AccessArticle
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
Pathogens 2020, 9(3), 209; https://doi.org/10.3390/pathogens9030209 - 12 Mar 2020
Cited by 1
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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Open AccessArticle
Adenovirus-vectored African Swine Fever Virus Antigens Cocktail Is Not Protective against Virulent Arm07 Isolate in Eurasian Wild Boar
Pathogens 2020, 9(3), 171; https://doi.org/10.3390/pathogens9030171 - 28 Feb 2020
Cited by 1
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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Open AccessCommunication
No Experimental Evidence of Co-Feeding Transmission of African Swine Fever Virus between Ornithodoros Soft Ticks
Pathogens 2020, 9(3), 168; https://doi.org/10.3390/pathogens9030168 - 28 Feb 2020
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)
Open AccessArticle
Drivers, Risk Factors and Dynamics of African Swine Fever Outbreaks, Southern Highlands, Tanzania
Pathogens 2020, 9(3), 155; https://doi.org/10.3390/pathogens9030155 - 25 Feb 2020
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

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Open AccessReview
Protective Properties of Attenuated Strains of African Swine Fever Virus Belonging to Seroimmunotypes I–VIII
Pathogens 2020, 9(4), 274; https://doi.org/10.3390/pathogens9040274 - 09 Apr 2020
Cited by 1
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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Open AccessBrief Report
Modulation of Type I Interferon System by African Swine Fever Virus
Pathogens 2020, 9(5), 361; https://doi.org/10.3390/pathogens9050361 - 09 May 2020
Cited by 1
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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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Drivers, risk factors and dynamics of African swine fever outbreaks, Southern Highlands, Tanzania
Dr. Folorunso Oludayo Fasina
 
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