African Swine Fever and Other Swine Viral Diseases in Africa

A special issue of Viruses (ISSN 1999-4915). This special issue belongs to the section "Animal Viruses".

Deadline for manuscript submissions: closed (20 November 2022) | Viewed by 15942

Special Issue Editors

Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
Interests: Epidemiology and control of African swine fever (ASF) and other infectious diseases of swine; management of ASF and biosecurity in smallholder and traditional pig production systems; integrating livestock production and biodiversity conservation at the wildlife/livestock interface; alternative policies and standards for trade in livestock and livestock commodities to enable export from areas not free of trade-sensitive transboundary animal diseases
Special Issues, Collections and Topics in MDPI journals
ARC-Onderstepoort Veterinary Research – Transboundary Animal Diseases Programme, Pretoria, South Africa
Interests: Transboundary Animal Diseases Diagnostics; Transboundary Animal Diseases Research; Foot and mouth Disease; African swine fever; Peste des petits ruminants
International Livestock Research Institute (ILRI), Nairobi, Kenya
Interests: epidemiology and control of African swine fever (ASF) and Pestes des Petit Ruminants (PPR)

Special Issue Information

Dear Colleagues,

Pig production is increasing in importance in Africa due to an increasing demand for affordable high-quality protein in response to rapid urban expansion. It is failing to reach its full potential due to various challenges, including diseases such as African swine fever (ASF), which evolved in Africa in an ancient sylvatic cycle between common warthogs (Phacochoerus africanus) and argasid ticks of the Ornithodoros moubata complex that live in their burrows. The disease has spread from its area of origin in eastern and southern Africa to most countries in sub-Saharan Africa that have domestic pig populations and beyond its borders to become the most feared disease of pigs on all five continents. Although Africa is home to only five per cent of the global pig population, pig production makes an important contribution to household income, improved nutrition, and food security. More than 70% of Africa’s pigs are farmed in traditional free-range smallholder/backyard farms with low or no biosecurity. Short cycle species like pigs are increasingly recognized as ideal species for farming in resource-poor settings due to their ability to produce large quantities of high quality protein in low input systems on little land that can be farmed by women, unemployed youth, and the elderly. In parts of Africa, pigs also have important cultural significance. The prevalence of ASF on the continent prevents pigs from reaching their true potential to alleviate poverty and provide incomes and better nutrition for the vulnerable due to both high mortality decimating the pigs and being a disincentive for investment in the pig sector. Managing ASF in Africa requires an innovative, multi-sectoral approach. Research is needed to provide in-depth knowledge of the virus, the hosts, and the environment to enable the mitigation of the disease.

For this Special Issue, we invite contributions on ASF research in Africa that will allow for a better understanding of the multiple genotypes of the virus to improve diagnostics and control on the continent; the immune response and genetic make-up of African domestic pigs and wild host reservoirs and vectors of the virus; and pig production systems, value chains, and socio-economic issues and their role in the maintenance and spread of ASF. While research on pigs focuses strongly on ASF due to the global interest in the disease, other viral diseases are neglected. Some of these are (or may already be) present, while others are likely to emerge with increasing intensification of pig production. This special edition invites contributions on any existing research on other porcine viral diseases in Africa

Prof. Dr. Mary-Louise Penrith
Dr. Livio Heath
Dr. Edward Abworo Okoth
Guest Editors

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Keywords

  • African swine fever
  • virology
  • epidemiology (descriptive and analytical)
  • molecular genetics
  • innovative approaches to control
  • pork production systems and value chains in context of ASF
  • risk analysis
  • genetics of wild African Suidae and local breed pigs
  • transmission at the wildlife interface and in smallholder production systems
  • socio-economics of ASF in African contexts

Published Papers (8 papers)

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Editorial

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2 pages, 164 KiB  
Editorial
Special Issue “African Swine Fever and Other Swine Viral Diseases in Africa”
by Mary-Louise Penrith, Edward Okoth and Livio Heath
Viruses 2023, 15(7), 1438; https://doi.org/10.3390/v15071438 - 26 Jun 2023
Viewed by 790
Abstract
African swine fever (ASF) has become the swine disease of most global concern since its second escape from Africa in 2007 resulted in its spread to five continents and the consequent devastation of industrial to subsistence pig farming [...] Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)

Research

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13 pages, 6759 KiB  
Article
Identification of Two Novel Linear B Cell Epitopes on the CD2v Protein of African Swine Fever Virus Using Monoclonal Antibodies
by Wenting Jiang, Dawei Jiang, Lu Li, Jiabin Wang, Panpan Wang, Xuejian Shi, Qi Zhao, Boyuan Liu, Pengchao Ji and Gaiping Zhang
Viruses 2023, 15(1), 131; https://doi.org/10.3390/v15010131 - 31 Dec 2022
Cited by 3 | Viewed by 1444
Abstract
African swine fever virus (ASFV) is a highly infectious viral pathogen that endangers the global pig industry, and no effective vaccine is available thus far. The CD2v protein is a glycoprotein on the outer envelope of ASFV, which mediates the transmission of the [...] Read more.
African swine fever virus (ASFV) is a highly infectious viral pathogen that endangers the global pig industry, and no effective vaccine is available thus far. The CD2v protein is a glycoprotein on the outer envelope of ASFV, which mediates the transmission of the virus in the blood and recognition of the virus serotype, playing an important role in ASFV vaccine development and disease prevention. Here, we generated two specific monoclonal antibodies (mAbs), 6C11 and 8F12 (subtype IgG1/kappa-type), against the ASFV CD2v extracellular domain (CD2v-ex, GenBank: MK128995.1, 1–588 bp) and characterized their specificity. Peptide scanning technology was used to identify the epitopes recognized by mAbs 6C11 and 8F12. As a result, two novel B cell epitopes, 38DINGVSWN45 and 134GTNTNIY140, were defined. Amino acid sequence alignment showed that the defined epitopes were conserved in all referenced ASFV strains from various regions of China including the highly pathogenic, epidemic strain, Georgia2007/1 (NC_044959.2), with the same noted substitutions compared to the four foreign ASFV wild-type strains. This study provides important reference values for the design and development of an ASFV vaccine and useful biological materials for the functional study of the CD2v protein by deletion analysis. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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10 pages, 2808 KiB  
Article
Development of an Effective Double Antigen Sandwich ELISA Based on p30 Protein to Detect Antibodies against African Swine Fever Virus
by Mengxiang Wang, Jinxing Song, Junru Sun, Yongkun Du, Xiaodong Qin, Lu Xia, Yanan Wu and Gaiping Zhang
Viruses 2022, 14(10), 2170; https://doi.org/10.3390/v14102170 - 30 Sep 2022
Cited by 10 | Viewed by 2170
Abstract
African swine fever (ASF), the highly lethal swine infectious disease caused by the African swine fever virus (ASFV), is a great threat to the swine industry. There is no effective vaccine or diagnostic method to prevent and control this disease currently. The p30 [...] Read more.
African swine fever (ASF), the highly lethal swine infectious disease caused by the African swine fever virus (ASFV), is a great threat to the swine industry. There is no effective vaccine or diagnostic method to prevent and control this disease currently. The p30 protein of ASFV is an important target for serological diagnosis, expressed in the early stage of viral replication and has high immunogenicity and sequence conservatism. Here, the CP204L gene was cloned into the expression vector pET-30a (+), and the soluble p30 protein was successfully expressed in the E. coli prokaryotic expression system and then labeled with horseradish peroxidase (HRP) to be the enzyme-labeled antigen. Using the purified recombinant p30 protein, a double-antigen sandwich ELISA for ASFV antibody detection was developed. This method exhibits excellent specificity, sensitivity and reproducibility in clinical sample detection with lower cost and shorter production cycles. Taken together, this study provides technical support for antibody detection for ASFV. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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12 pages, 2821 KiB  
Article
Co-Deletion of A238L and EP402R Genes from a Genotype IX African Swine Fever Virus Results in Partial Attenuation and Protection in Swine
by Hussein M. Abkallo, Johanneke D. Hemmink, Bernard Oduor, Emmanuel M. Khazalwa, Nicholas Svitek, Nacyra Assad-Garcia, Jeremiah Khayumbi, Walter Fuchs, Sanjay Vashee and Lucilla Steinaa
Viruses 2022, 14(9), 2024; https://doi.org/10.3390/v14092024 - 13 Sep 2022
Cited by 8 | Viewed by 2055
Abstract
African swine fever virus (ASFV) is the causative agent of African swine fever (ASF), resulting in up to 100% mortality in pigs. Although endemic in most sub-Saharan African countries, where all known ASFV genotypes have been reported, the disease has caused pandemics of [...] Read more.
African swine fever virus (ASFV) is the causative agent of African swine fever (ASF), resulting in up to 100% mortality in pigs. Although endemic in most sub-Saharan African countries, where all known ASFV genotypes have been reported, the disease has caused pandemics of significant economic impact in Eurasia, and no vaccines or therapeutics are available to date. In endeavors to develop live-attenuated vaccines against ASF, deletions of several of the ~170 ASFV genes have shown contrasting results depending on the genotype of the investigated ASFV. Here, we report the in vivo outcome of a single deletion of the A238L (5EL) gene and double deletions of A238L (5EL) and EP402R (CD2v) genes from the genome of a highly virulent genotype IX ASFV isolate. Domestic pigs were intramuscularly inoculated with (i) ASFV-Ke-ΔA238L to assess the safety of A238L deletion and (ii) ASFV-Ke-ΔEP402RΔA238L to investigate protection against challenge with the virulent wildtype ASFV-Ke virus. While A238L (5EL) gene deletion did not yield complete attenuation, co-deletion of A238L (5EL) and EP402R (CD2v) improved the safety profile of the single deletions, eliciting both humoral and cellular immune responses and conferred partial protection against challenge with the virulent wildtype ASFV-Ke virus. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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11 pages, 1934 KiB  
Article
Deletion of the CD2v Gene from the Genome of ASFV-Kenya-IX-1033 Partially Reduces Virulence and Induces Protection in Pigs
by Johanneke D. Hemmink, Emmanuel M. Khazalwa, Hussein M. Abkallo, Bernard Oduor, Jeremiah Khayumbi, Nicholas Svitek, Sonal P. Henson, Sandra Blome, Günther Keil, Richard P. Bishop and Lucilla Steinaa
Viruses 2022, 14(9), 1917; https://doi.org/10.3390/v14091917 - 30 Aug 2022
Cited by 11 | Viewed by 1802
Abstract
Infection of pigs with the African swine fever virus (ASFV) leads to a devastating hemorrhagic disease with a high mortality of up to 100%. In this study, a CD2v gene deletion was introduced to a genotype IX virus from East Africa, ASFV-Kenya-IX-1033 (ASFV-Kenya-IX-1033-∆CD2v), [...] Read more.
Infection of pigs with the African swine fever virus (ASFV) leads to a devastating hemorrhagic disease with a high mortality of up to 100%. In this study, a CD2v gene deletion was introduced to a genotype IX virus from East Africa, ASFV-Kenya-IX-1033 (ASFV-Kenya-IX-1033-∆CD2v), to investigate whether this deletion led to reduced virulence in domestic pigs and to see if inoculation with this LA-ASFV could induce protective immunity against parental virus challenge. All pigs inoculated with ASFV-Kenya-IX-1033-ΔCD2v survived inoculation but presented with fever, reduced appetite and lethargy. ASFV genomic copies were detected in only one animal at one time point. Seven out of eight animals survived subsequent challenge with the pathogenic parental strain (87.5%) but had mild to moderate clinical symptoms and had a gross pathology compatible with chronic ASFV infection. All mock-immunised animals developed acute ASF upon challenge with ASFV-Kenya-IX-1033 and were euthanised upon meeting the humane endpoint criteria. ASFV genome copy numbers after challenge were similar in the two groups. ASFV-Kenya-IX-1033-∆CD2v is therefore a useful tool to investigate the development of immunity to ASFV genotype IX, but safety concerns preclude its use as a candidate vaccine without further attenuation. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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12 pages, 3777 KiB  
Article
The African Swine Fever Isolate ASFV-Kenya-IX-1033 Is Highly Virulent and Stable after Propagation in the Wild Boar Cell Line WSL
by Johanneke D. Hemmink, Hussein M. Abkallo, Sonal P. Henson, Emmanuel M. Khazalwa, Bernard Oduor, Anna Lacasta, Edward Okoth, Victor Riitho, Walter Fuchs, Richard P. Bishop and Lucilla Steinaa
Viruses 2022, 14(9), 1912; https://doi.org/10.3390/v14091912 - 29 Aug 2022
Cited by 7 | Viewed by 2081
Abstract
We describe the characterization of an African swine fever genotype IX virus (ASFV-Kenya-IX-1033), which was isolated from a domestic pig in western Kenya during a reported outbreak. This includes the efficiency of virus replication and in vivo virulence, together with genome stability and [...] Read more.
We describe the characterization of an African swine fever genotype IX virus (ASFV-Kenya-IX-1033), which was isolated from a domestic pig in western Kenya during a reported outbreak. This includes the efficiency of virus replication and in vivo virulence, together with genome stability and virulence, following passage in blood macrophages and in a wild boar lung cell line (WSL). The ASFV-Kenya-IX-1033 stock retained its ability to replicate in primary macrophages and retained virulence in vivo, following more than 20 passages in a WSL. At the whole genome level, a few single-nucleotide differences were observed between the macrophage and WSL-propagated viruses. Thus, we propose that the WSL is suitable for the production of live-attenuated ASFV vaccine candidates based on the modification of this wild-type isolate. The genome sequences for ASFV-Kenya-IX-1033 propagated in macrophages and in WSL cells were submitted to GenBank, and a challenge model based on the isolate was developed. This will aid the development of vaccines against the genotype IX ASFV circulating in eastern and central Africa. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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23 pages, 12524 KiB  
Article
Detection of African Swine Fever Virus in Ornithodoros Tick Species Associated with Indigenous and Extralimital Warthog Populations in South Africa
by Anthony F. Craig, Mathilde L. Schade-Weskott, Thapelo Rametse, Livio Heath, Gideon J. P. Kriel, Lin-Mari de Klerk-Lorist, Louis van Schalkwyk, Jessie D. Trujillo, Jan E. Crafford, Juergen A. Richt and Robert Swanepoel
Viruses 2022, 14(8), 1617; https://doi.org/10.3390/v14081617 - 26 Jul 2022
Cited by 3 | Viewed by 2277
Abstract
We investigated the possibility that sylvatic circulation of African swine fever virus (ASFV) in warthogs and Ornithodoros ticks had extended beyond the historically affected northern part of South Africa that was declared a controlled area in 1935 to prevent the spread of infection [...] Read more.
We investigated the possibility that sylvatic circulation of African swine fever virus (ASFV) in warthogs and Ornithodoros ticks had extended beyond the historically affected northern part of South Africa that was declared a controlled area in 1935 to prevent the spread of infection to the rest of the country. We recently reported finding antibody to the virus in extralimital warthogs in the south of the country, and now describe the detection of infected ticks outside the controlled area. A total of 5078 ticks was collected at 45 locations in 7/9 provinces during 2019–2021 and assayed as 711 pools for virus content by qPCR, while 221 pools were also analysed for tick phylogenetics. Viral nucleic acid was detected in 50 tick pools representing all four members of the Ornithodoros (Ornithodoros) moubata complex known to occur in South Africa: O. (O.) waterbergensis and O. (O.) phacochoerus species yielded ASFV genotypes XX, XXI, XXII at 4 locations and O. (O.) moubata yielded ASFV genotype I at two locations inside the controlled area. Outside the controlled area, O. (O.) moubata and O. (O.) compactus ticks yielded ASFV genotype I at 7 locations, while genotype III ASFV was identified in O. (O.) compactus ticks at a single location. Two of the three species of the O. (O.) savignyi complex ticks known to be present in the country, O. (O.) kalahariensis and O. (O.) noorsveldensis, were collected at single locations and found negative for virus. The only member of the Pavlovskyella subgenus of Ornithodoros ticks known to occur in South Africa, O. (P.) zumpti, was collected from warthog burrows for the first time, in Addo National Park in the Eastern Cape Province where ASFV had never been recorded, and it tested negative for the viral nucleic acid. While it is confirmed that there is sylvatic circulation of ASFV outside the controlled area in South Africa, there is a need for more extensive surveillance and for vector competence studies with various species of Ornithodoros ticks. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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Other

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21 pages, 1238 KiB  
Systematic Review
Identification of Risk Factors for African Swine Fever: A Systematic Review
by Hannes Bergmann, Johanna Dups-Bergmann, Katja Schulz, Carolina Probst, Laura Zani, Melina Fischer, Jörn Gethmann, Nicolai Denzin, Sandra Blome, Franz J. Conraths and Carola Sauter-Louis
Viruses 2022, 14(10), 2107; https://doi.org/10.3390/v14102107 - 23 Sep 2022
Cited by 6 | Viewed by 2448
Abstract
African swine fever (ASF) is an internationally-spreading viral pig disease that severely damages agricultural pork production and trade economy as well as social welfare in disease-affected regions. A comprehensive understanding of ASF risk factors is imperative for efficient disease control. As the absence [...] Read more.
African swine fever (ASF) is an internationally-spreading viral pig disease that severely damages agricultural pork production and trade economy as well as social welfare in disease-affected regions. A comprehensive understanding of ASF risk factors is imperative for efficient disease control. As the absence of effective ASF vaccines limits disease management options, the identification and minimisation of ASF-associated risk factors is critical to preventing ASF outbreaks. Here, we compile currently known potential ASF risk factors identified through a systematic literature review. We found 154 observation-based and 1239 potential ASF risk factors, which we were able to group into the following defined risk categories: ‘ASF-virus’, ‘Biosecurity’, ‘Disease control’, ‘Environment’, ‘Husbandry’, ‘Movement’, ‘Network’, ‘Pig’, ‘Society’ and ‘Surveillance’. Throughout the epidemiological history of ASF there have been similar risk categories, such as ‘Environment’-related risk factors, predominantly reported in the literature irrespective of the ASF situation at the time. While ASF risk factor reporting has markedly increased since 2010, the majority of identified risk factors overall have referred to domestic pigs. The reporting of risk factors for ASF in wild boar mostly commenced from 2016 onwards. The compendium of ASF risk factors presented herein defines our current knowledge of ASF risk factors, and critically informs ASF-related problem solving. Full article
(This article belongs to the Special Issue African Swine Fever and Other Swine Viral Diseases in Africa)
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