Detection of African swine fever virus in pigs in Southwest Nigeria

Background and Aim: Nigeria experienced repeated outbreaks of African swine fever (ASF) in pig herds between 1997 and 2005 in the southwest region of the country. ASF is believed to currently be enzootic in this region. The status of enzootic transmission of ASF virus strain to pigs is; however, unknown. Twenty-three genotypes of the ASF virus based on the p72 gene are found across Africa. This study aimed to identify the current circulating field strain(s) of the ASF virus in Southwest Nigeria and characterized evolutionary trends. Materials and Methods: DNA samples were extracted from 144 pooled blood samples obtained from 2012 to 2013 following the manufacturer's instructions. DNA was used for conventional polymerase chain reaction using primers targeting the p72 gene and amplified products sequenced with Sanger's sequencing. Sequences were analyzed for homology and phylogenetic relationships. Results: Eleven of 144 samples (7.6%) showed bands at 950 bp. A new field strain of ASF virus of genotype I that shared ancestry with ASF virus strains or isolates from Spain and Brazil was identified among pig herds. The new strain differs phylogenetically in amino acid composition compared with previously identified ASF virus field strains. Conclusion: The currently circulating field strain of ASF virus suggests a mutation responsible for decreased morbidity and mortality recorded in sporadic cases.

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Live Attenuated African Swine Fever Viruses as Ideal Tools to Dissect the Mechanisms Involved in Cross-Protection

Viruses ◽

10.3390/v12121474 ◽

2020 ◽

Vol 12 (12) ◽

pp. 1474

Author(s):

Elisabeth Lopez ◽

Juanita van Heerden ◽

Laia Bosch-Camós ◽

Francesc Accensi ◽

Maria Jesus Navas ◽

...

Keyword(s):

Vaccine Development ◽

African Swine Fever Virus ◽

Virulent Strain ◽

Sequence Similarity ◽

Clinical Signs ◽

African Swine Fever ◽

Cross Protection ◽

Sub Saharan Africa ◽

Genotype I ◽

Genotype Ii

African swine fever (ASF) has become the major threat for the global swine industry. Furthermore, the epidemiological situation of African swine fever virus (ASFV) in some endemic regions of Sub-Saharan Africa is worse than ever, with multiple virus strains and genotypes currently circulating in a given area. Despite the recent advances on ASF vaccine development, there are no commercial vaccines yet, and most of the promising vaccine prototypes available today have been specifically designed to fight the genotype II strains currently circulating in Europe, Asia, and Oceania. Previous results from our laboratory have demonstrated the ability of BA71∆CD2, a recombinant LAV lacking CD2v, to confer protection against homologous (BA71) and heterologous genotype I (E75) and genotype II (Georgia2007/01) ASFV strains, both belonging to same clade (clade C). Here, we extend these results using BA71∆CD2 as a tool trying to understand ASFV cross-protection, using phylogenetically distant ASFV strains. We first observed that five out of six (83.3%) of the pigs immunized once with 106 PFU of BA71∆CD2 survived the tick-bite challenge using Ornithodoros sp. soft ticks naturally infected with RSA/11/2017 strain (genotype XIX, clade D). Second, only two out of six (33.3%) survived the challenge with Ken06.Bus (genotype IX, clade A), which is phylogenetically more distant to BA71∆CD2 than the RSA/11/2017 strain. On the other hand, homologous prime-boosting with BA71∆CD2 only improved the survival rate to 50% after Ken06.Bus challenge, all suffering mild ASF-compatible clinical signs, while 100% of the pigs immunized with BA71∆CD2 and boosted with the parental BA71 virulent strain survived the lethal challenge with Ken06.Bus, without almost no clinical signs of the disease. Our results confirm that cross-protection is a multifactorial phenomenon that not only depends on sequence similarity. We believe that understanding this complex phenomenon will be useful for designing future vaccines for ASF-endemic areas.

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Differential vector competence of Ornithodoros soft ticks for African swine fever virus: What if it involves more than just crossing organic barriers in ticks?

Parasites & Vectors ◽

10.1186/s13071-020-04497-1 ◽

2020 ◽

Vol 13 (1) ◽

Author(s):

Rémi Pereira De Oliveira ◽

Evelyne Hutet ◽

Renaud Lancelot ◽

Frédéric Paboeuf ◽

Maxime Duhayon ◽

...

Keyword(s):

Viral Replication ◽

Vertical Transmission ◽

African Swine Fever Virus ◽

Vector Competence ◽

African Swine Fever ◽

Realistic Model ◽

Molecular Data ◽

Fever Virus ◽

Genotype I ◽

Genotype Ii

Abstract Background Several species of soft ticks in genus Ornithodoros are known vectors and reservoirs of African swine fever virus (ASFV). However, the underlying mechanisms of vector competence for ASFV across Ornithodoros species remain to be fully understood. To that end, this study compared ASFV replication and dissemination as well as virus vertical transmission to descendants between Ornithodorosmoubata, O. erraticus, and O. verrucosus in relation to what is known about the ability of these soft tick species to transmit ASFV to pigs. To mimic the natural situation, a more realistic model was used where soft ticks were exposed to ASFV by allowing them to engorge on viremic pigs. Methods Ornithodoros moubata ticks were infected with the ASFV strains Liv13/33 (genotype I) or Georgia2007/1 (genotype II), O. erraticus with OurT88/1 (genotype I) or Georgia2007/1 (genotype II), and O. verrucosus with Ukr12/Zapo (genotype II), resulting in five different tick–virus pairs. Quantitative PCR (qPCR) assays targeting the VP72 ASFV gene was carried out over several months on crushed ticks to study viral replication kinetics. Viral titration assays were also carried out on crushed ticks 2 months post infection to confirm virus survival in soft ticks. Ticks were dissected. and DNA was individually extracted from the following organs to study ASFV dissemination: intestine, salivary glands, and reproductive organs. DNA extracts from each organ were tested by qPCR. Lastly, larval or first nymph-stage progeny emerging from hatching eggs were tested by qPCR to assess ASFV vertical transmission. Results Comparative analyses revealed higher rates of ASFV replication and dissemination in O. moubata infected with Liv13/33, while the opposite was observed for O. erraticus infected with Georgia2007/1 and for O. verrucosus with Ukr12/Zapo. Intermediate profiles were found for O. moubata infected with Georgia2007/1 and for O. erraticus with OurT88/1. Vertical transmission occurred efficiently in O. moubata infected with Liv13/33, and at very low rates in O. erraticus infected with OurT88/1. Conclusions This study provides molecular data indicating that viral replication and dissemination in Ornithodoros ticks are major mechanisms underlying ASFV horizontal and vertical transmission. However, our results indicate that other determinants beyond viral replication also influence ASFV vector competence. Further research is required to fully understand this process in soft ticks.

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Identification and Isolation of Two Different Subpopulations Within African Swine Fever Virus Arm/07 Stock

Vaccines ◽

10.3390/vaccines8040625 ◽

2020 ◽

Vol 8 (4) ◽

pp. 625

Author(s):

Daniel Pérez-Núñez ◽

Eva Castillo-Rosa ◽

Gonzalo Vigara-Astillero ◽

Raquel García-Belmonte ◽

Carmina Gallardo ◽

...

Keyword(s):

Vaccine Development ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Fever Virus ◽

Single Mutation ◽

High Sequence Identity ◽

Genotype I ◽

High Coverage ◽

Purification Method

No efficient vaccines exist against African swine fever virus (ASFV), which causes a serious disease in wild boars and domestic pigs that produces great industrial and ecological concerns worldwide. An extensive genetic characterization of the original ASFV stocks used to produce live attenuated vaccine (LAV) prototypes is needed for vaccine biosecurity and control. Here, we sequenced for the first time the Arm/07 stock which was obtained from an infected pig during the Armenia outbreak in 2007, using an improved viral dsDNA purification method together with high coverage analysis. There was unexpected viral heterogeneity within the stock, with two genetically distinct ASFV subpopulations. The first, represented by the Arm/07/CBM/c2 clone, displayed high sequence identity to the updated genotype II Georgia 2007/1, whereas the second (exemplified by clone Arm/07/CBM/c4) displayed a hemadsorbing phenotype and grouped within genotype I based on a central region conserved among all members of this group. Intriguingly, Arm/07/CBM/c4 contained a unique EP402R sequence, produced by a single mutation in the N-terminal region. Importantly, Arm/07/CBM/c4 showed in vitro features of attenuated strains regarding innate immune response pathway. Both Arm/07/CBM/c2 and c4 represent well-characterized viral clones, useful for different molecular and virus-host interaction studies, including virulence studies and vaccine development.

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Immunization of African Indigenous Pigs with Attenuated Genotype I African Swine Fever Virus OURT88/3 Induces Protection Against Challenge with Virulent Strains of Genotype I

Transboundary and Emerging Diseases ◽

10.1111/tbed.12303 ◽

2015 ◽

Vol 63 (5) ◽

pp. e323-e327 ◽

Cited By ~ 22

Author(s):

L. K. Mulumba-Mfumu ◽

L. C. Goatley ◽

C. Saegerman ◽

H.-H. Takamatsu ◽

L. K. Dixon

Keyword(s):

African Swine Fever Virus ◽

African Swine Fever ◽

Fever Virus ◽

Genotype I ◽

Virulent Strains ◽

Indigenous Pigs

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African Swine Fever in Cameroon: A Review

Pathogens ◽

10.3390/pathogens10040421 ◽

2021 ◽

Vol 10 (4) ◽

pp. 421

Author(s):

Ebanja Joseph Ebwanga ◽

Stephen Mbigha Ghogomu ◽

Jan Paeshuyse

Keyword(s):

African Swine Fever Virus ◽

Central Africa ◽

African Swine Fever ◽

Fever Virus ◽

Economic Losses ◽

Future Research ◽

Genotype I ◽

Traditional System ◽

Pork Industry ◽

Domestic Cycle

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.

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Role of African swine fever virus (ASFV) proteins EP153R and EP402R in reducing viral persistence in blood and virulence in pigs infected with BeninΔDP148R

Journal of Virology ◽

10.1128/jvi.01340-21 ◽

2021 ◽

Author(s):

Vlad Petrovan ◽

Anusyah Rathakrishnan ◽

Muneeb Islam ◽

Lynnette C. Goatley ◽

Katy Moffat ◽

...

Keyword(s):

Vaccine Development ◽

African Swine Fever Virus ◽

Clinical Signs ◽

African Swine Fever ◽

Fever Virus ◽

Genotype I ◽

Virus Persistence ◽

Challenge Virus

The limited knowledge on the role of many of the approximately 170 proteins encoded by African swine fever virus restricts progress towards vaccine development. Previously, the DP148R gene was deleted from the genome of genotype I virulent Benin 97/1 isolate. This virus, BeninΔDP148R, induced transient moderate clinical signs after immunization and high levels of protection against challenge. However, the BeninΔDP148R virus and genome persisted in blood over a prolonged period. In the current study deletion of either EP402R or EP153R genes individually or in combination from BeninΔDP148R genome was shown not to reduce virus replication in macrophages in vitro. However, deletion of EP402R dramatically reduced the period of infectious virus persistence in blood in immunized pigs from 28 to 14 days and virus genome from 59 to 14 days, whilst maintaining high levels of protection against challenge. The additional deletion of EP153R (BeninΔDP148RΔEP153RΔEP402R) further attenuated the virus and no viremia or clinical signs were observed post-immunization. This was associated with decreased protection and detection of moderate levels of challenge virus in blood. Interestingly, the deletion of EP153R alone from BeninΔDP148R did not result in further virus attenuation and did not reduce the period of virus persistence in blood. These results show that EP402R and EP153R have a synergistic role in reducing clinical signs and levels of virus in blood. Importance: African swine fever virus (ASFV) causes a disease of domestic pigs and wild boar which results in death of almost all infected animals. The disease has a high economic impact, and no vaccine is available. We investigated the role of two ASFV proteins, called EP402R and EP153R, in determining the levels and length of time virus persists in blood from infected pigs. EP402R causes ASFV particles and infected cells to bind to red blood cells. Deletion of the EP402R gene dramatically reduced virus persistence in blood but did not reduce the level of virus. Deletion of the EP153R alone did not reduce the period or level of virus persistence in blood. However, deleting both EP153R and EP402R resulted in undetectable levels of virus in blood and no clinical signs showing the proteins act synergistically. Importantly the infected pigs were protected following infection with the wildtype virus that kills pigs.

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African Swine Fever: Disease Dynamics in Wild Boar Experimentally Infected with ASFV Isolates Belonging to Genotype I and II

Viruses ◽

10.3390/v11090852 ◽

2019 ◽

Vol 11 (9) ◽

pp. 852 ◽

Cited By ~ 11

Author(s):

Sánchez-Cordón ◽

Nunez ◽

Neimanis ◽

Wikström-Lassa ◽

Montoya ◽

...

Keyword(s):

Immune Response ◽

Wild Boar ◽

Western Europe ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Relevant Information ◽

Disease Spread ◽

Wild Boar Population ◽

Disease Pathogenesis ◽

Genotype I

After the re-introduction of African swine fever virus (ASFV) genotype II isolates into Georgia in 2007, the disease spread from Eastern to Western Europe and then jumped first up to Mongolian borders and later into China in August 2018, spreading out of control and reaching different countries of Southeast Asia in 2019. From the initial incursion, along with domestic pigs, wild boar displayed a high susceptibility to ASFV and disease development. The disease established self-sustaining cycles within the wild boar population, a key fact that helped its spread and that pointed to the wild boar population as a substantial reservoir in Europe and probably also in Asia, which may hinder eradication and serve as the source for further geographic expansion. The present review gathers the most relevant information available regarding infection dynamics, disease pathogenesis and immune response that experimental infections with different ASFV isolates belonging to genotype I and II in wild boar and feral pigs have generated. Knowledge gaps in areas such as disease pathogenesis and immune response highlights the importance of focusing future studies on unravelling the early mechanisms of virus-cell interaction and innate and/or adaptive immune responses, knowledge that will contribute to the development of efficacious treatments/vaccines against ASFV.

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Coding-Complete Genome Sequence of an African Swine Fever Virus Strain Liv13/33 Isolate from Experimental Transmission between Pigs and Ornithodoros moubata Ticks

Microbiology Resource Announcements ◽

10.1128/mra.00185-20 ◽

2020 ◽

Vol 9 (17) ◽

Cited By ~ 1

Author(s):

Amélie Chastagner ◽

Rémi Pereira de Oliveira ◽

Evelyne Hutet ◽

Mireille Le Dimna ◽

Frédéric Paboeuf ◽

...

Keyword(s):

Genome Sequence ◽

Virus Strain ◽

Complete Genome Sequence ◽

Complete Genome ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Genotype I ◽

Experimental Transmission ◽

Content Type ◽

Ornithodoros Moubata

Here, we report the coding-complete genome sequence of African swine fever (ASF) virus strain Liv13/33, isolated from experimentally infected pigs and Ornithodoros moubata ticks. The 11 sequences that we obtained harbored no notable differences to each other, and all of them were closely related to the genome sequence of the Mkuzi 1979 strain of genotype I.

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First Genomic Evidence of Dual African Swine Fever Virus Infection: Case Report from Recent and Historical Outbreaks in Sardinia

Viruses ◽

10.3390/v13112145 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2145

Author(s):

Mariangela Stefania Fiori ◽

Luca Ferretti ◽

Matteo Floris ◽

Federica Loi ◽

Antonello Di Nardo ◽

...

Keyword(s):

Case Report ◽

Virus Infection ◽

Wild Boar ◽

Phylogenetic Relationship ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Fever Virus ◽

Genotype I ◽

Genome Wide ◽

Dual Infections

African swine fever virus (ASFV) is one of the pathogens of highest concern worldwide. Despite different virus lineages co-circulating in several areas, dual infections in the same animal have been rarely observed, suggesting that ASF superinfections are infrequent events. Here we present the first genome-wide detection and analysis of two intragenotype dual ASFV infections. The dual infections have been detected in a hunted wild boar and in a pig carcass, both infected by ASFV genotype I in Sardinia in 1984 and 2018, respectively. We characterize the genetic differences between the two sequences, their intra-host frequency, and their phylogenetic relationship among fully sequenced ASFV strains from Sardinia. Both dual infections involve pairs of closely related but different viruses that were circulating in Sardinia in the same period. The results imply that dual ASFV infections or similar ASFV strains are more common than expected, especially in ASF endemic areas, albeit difficult to detect.

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