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M. L. Penrith - One of the best experts on this subject based on the ideXlab platform.
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Understanding African swine fever outbreaks in domestic pigs in a Sylvatic endemic area: The case of the South African controlled area between 1977–2017
Transboundary and emerging diseases, 2020Co-Authors: Leana Janse Van Rensburg, M. L. Penrith, E. Etter, Livio Heath, Juanita HeerdenAbstract:South Africa declared a controlled area for African swine fever (ASF) in 1935, consisting of the northern parts of Limpopo, Mpumalanga, North West and Kwa-Zulu Natal Provinces. The area was delineated based on the endemic presence of the Sylvatic Cycle of ASF, involving warthogs and argasid ticks. Occasionally, spillover occurs from the Sylvatic Cycle to domestic pigs, causing ASF outbreaks. In the period 1977 to 2017, 59 outbreaks of ASF were reported in domestic pigs within the ASF controlled area of South Africa. During these outbreaks, at least 4,031 domestic pigs either died or were culled. Season did not affect the number of reported ASF outbreaks, but the number of reported outbreaks in this area per year was thought to be slowly increasing, although not statistically significant. Outbreaks occurred predominantly in Limpopo province (93%) and were mostly due to contact (or suspected contact) with warthog or warthog carcasses. Clustering analysis of outbreaks found that the local municipalities of Ramotshere Moiloa, Lephalale and Thabazimbi had the highest relative risk for outbreaks. In 32 of the 59 outbreaks, the genotype of the ASF virus (ASFV) involved could be determined. Phylogenetic analysis of ASFVs detected in domestic pigs during the study period revealed that p72 genotypes I, III, IV, VII, VIII, XIX, XX, XXI and XXII had been involved in causing outbreaks within the ASF controlled area. No outbreaks were reported in the Kwa-Zulu Natal part of the controlled area during this period. South Africa is unlikely to eradicate all sources of ASFV as spillover from the Sylvatic Cycle in the controlled area continued to occur, but with the implementation of appropriate biosecurity measures pigs can be successfully farmed despite the presence of ASFV in African wild suids and soft ticks.
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Epidemiology of African swine fever in Africa today: Sylvatic Cycle versus socio-economic imperatives
Transboundary and Emerging Diseases, 2019Co-Authors: M. L. Penrith, E. Etter, Armanda Duarte Bastos, Daniel Beltran-alcrudoAbstract:African swine fever (ASF) is believed to have evolved in eastern and southern Africa in a Sylvatic Cycle between common warthogs (Phacochoerus africanus) and argasid ticks of the Ornithodoros moubata complex that live in their burrows. The involvement of warthogs and possibly other wild suids in the maintenance of ASF virus means that the infection cannot be eradicated from Africa, but only prevented and controlled in domestic pig populations. Historically, outbreaks of ASF in domestic pigs in Africa were almost invariably linked to the presence of warthogs, but subsequent investigations of the disease in pigs revealed the presence of another Cycle involving domestic pigs and ticks, with a third Cycle becoming apparent when the disease expanded into West Africa where the Sylvatic Cycle is not present. The increase in ASF outbreaks that has accompanied the exponential growth of the African pig population over the last three decades has heralded a shift in the epidemiology of ASF in Africa, and the growing importance of the pig husbandry and trade in the maintenance and spread of ASF. This review, which focuses on the ASF situation between 1989 and 2017, suggests a minor role for wild suids compared with the domestic Cycle, driven by socio-economic factors that determine the ability of producers to implement the control measures needed for better management of ASF in Africa.
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Epidemiology of African swine fever in Africa today : Sylvatic Cycle versus socio‐economic imperatives
Transboundary and emerging diseases, 2019Co-Authors: M. L. Penrith, Armanda Duarte Bastos, Eric M.c. Etter, Daniel Beltrán‐alcrudoAbstract:African swine fever (ASF) is believed to have evolved in eastern and southern Africa in a Sylvatic Cycle between common warthogs (Phacochoerus africanus) and argasid ticks of the Ornithodoros moubata complex that live in their burrows. The involvement of warthogs and possibly other wild suids in the maintenance of ASF virus means that the infection cannot be eradicated from Africa, but only prevented and controlled in domestic pig populations. Historically, outbreaks of ASF in domestic pigs in Africa were almost invariably linked to the presence of warthogs, but subsequent investigations of the disease in pigs revealed the presence of another Cycle involving domestic pigs and ticks, with a third Cycle becoming apparent when the disease expanded into West Africa where the Sylvatic Cycle is not present. The increase in ASF outbreaks that has accompanied the exponential growth of the African pig population over the last three decades has heralded a shift in the epidemiology of ASF in Africa, and the growing importance of the pig husbandry and trade in the maintenance and spread of ASF. This review, which focuses on the ASF situation between 1989 and 2017, suggests a minor role for wild suids compared with the domestic Cycle, driven by socio‐economic factors that determine the ability of producers to implement the control measures needed for better management of ASF in Africa.
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african swine fever virus eradication in africa
Virus Research, 2013Co-Authors: M. L. Penrith, Ferran Jori, Wilna Vosloo, Armanda D.s. BastosAbstract:Abstract African swine fever was reported in domestic pigs in 26 African countries during the period 2009–2011. The virus exists in an ancient Sylvatic Cycle between warthogs ( Phacochoerus africanus ) and argasid ticks of the Ornithodoros moubata complex in many of the countries reporting outbreaks and in two further countries in the region. Eradication of the virus from the countries in eastern and southern Africa where the classic Sylvatic Cycle occurs is clearly not an option. However, the virus has become endemic in domestic pigs in 20 countries and the great majority of outbreaks in recent decades, even in some countries where the Sylvatic Cycle occurs, have been associated with movement of infected pigs and pig meat. Pig production and marketing and ASF control in Africa have been examined in order to identify risk factors for the maintenance and spread of ASF. These include large pig populations, traditional free-range husbandry systems, lack of biosecurity in semi-intensive and intensive husbandry systems, lack of organisation in both pig production and pig marketing that results in lack of incentives for investment in pig farming, and ineffective management of ASF. Most of these factors are linked to poverty, yet pigs are recognised as a livestock species that can be used to improve livelihoods and contribute significantly to food security. The changes needed and how they might be implemented in order to reduce the risk of ASF to pig producers in Africa and to the rest of the world are explored.
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Review of the Sylvatic Cycle of African swine fever in sub-Saharan Africa and the Indian ocean
Virus Research, 2013Co-Authors: Ferran Jori, Ludovic Vial, M. L. Penrith, R. Pérez-sánchez, E. Etter, Emmanuel Albina, Vincent Michaud, F. RogerAbstract:African swine fever (ASF) is a major limiting factor for pig production in most of the countries in Sub-Saharan Africa and the Indian Ocean. In the absence of vaccine, a good understanding of the ecology and epidemiology of the disease is fundamental to implement effective control measures. In selected countries of Southern and East Africa, the association between Ornithodoros moubata ticks and warthogs has been described in detail in the literature. However, for many other countries in the region, information related to the Sylvatic Cycle is lacking or incomplete. In West African countries, for instance, the role of wild pigs in the epidemiology of ASF has never been demonstrated and the existence and potential impact of a Sylvatic Cycle involving an association between soft ticks and warthogs is questionable. In other countries, other wild pig species such as the bushpigs (Potamochoerus spp.) can also be asymptomatically infected by the virus but their role in the epidemiology of the disease is unclear and might differ according to geographic regions. In addition, the methods and techniques required to study the role of wild hosts in ASF virus (ASFV) epidemiology and ecology are very specific and differ from the more traditional methods to study domestic pigs or other tick species. The aim of this review is (i) to provide a descriptive list of the methodologies implemented to study the role of wild hosts in African swine fever, (ii) to compile the available knowledge about the Sylvatic Cycle of ASFV in different regions of Sub-Saharan Africa and the Indian Ocean in addition to the one that has been described for East and Southern Africa, and (iii) to discuss current methodologies and available knowledge in order to identify new orientations for further field and experimental surveys.
Nikos Vasilakis - One of the best experts on this subject based on the ideXlab platform.
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Colonized Sabethes cyaneus, a Sylvatic New World Mosquito Species, Shows a Low Vector Competence for Zika Virus Relative to Aedes aegypti.
Viruses, 2018Co-Authors: Ajit K. Karna, Sasha R. Azar, Jessica A. Plante, Rumei Yun, Nikos Vasilakis, Scott C. Weaver, Immo A. Hansen, Kathryn A. HanleyAbstract:The introduction of Zika virus (ZIKV) to the Americas raised concern that the virus would spill back from human transmission, perpetuated by Aedes aegypti, into a Sylvatic Cycle maintained in wildlife and forest-living mosquitoes. In the Americas, Sabethes species are vectors of Sylvatic yellow fever virus (YFV) and are therefore candidate vectors of a Sylvatic ZIKV Cycle. To test the potential of Sabethes cyaneus to transmit ZIKV, Sa. cyaneus and Ae. aegypti were fed on A129 mice one or two days post-infection (dpi) with a ZIKV isolate from Mexico. Sa. cyaneus were sampled at 3, 4, 5, 7, 14, and 21 days post-feeding (dpf) and Ae. aegypti were sampled at 14 and 21 dpf. ZIKV was quantified in mosquito bodies, legs, and saliva to measure infection, dissemination, and potential transmission, respectively. Of 69 Sa. cyaneus that fed, ZIKV was detected in only one, in all body compartments, at 21 dpf. In contrast, at 14 dpf 100% of 20 Ae. aegypti that fed on mice at 2 dpi were infected and 70% had virus in saliva. These data demonstrate that Sa. cyaneus is a competent vector for ZIKV, albeit much less competent than Ae. aegypti.
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the emergence of arthropod borne viral diseases a global prospective on dengue chikungunya and zika fevers
Acta Tropica, 2017Co-Authors: Sandra V Mayer, Robert B. Tesh, Nikos VasilakisAbstract:Arthropod-borne viruses (arboviruses) present a substantial threat to human and animal health worldwide. Arboviruses can cause a variety of clinical presentations that range from mild to life threatening symptoms. Many arboviruses are present in nature through two distinct Cycles, the urban and Sylvatic Cycle that are maintained in complex biological Cycles. In this review we briefly discuss the factors driving the emergence of arboviruses, such as the anthropogenic aspects of unrestrained human population growth, economic expansion and globalization. Also the important aspects of viruses and vectors in the occurrence of arboviruses epidemics. The focus of this review will be on dengue, zika and chikungunya viruses, particularly because these viruses are currently causing a negative impact on public health and economic damage around the world.
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Potential for Zika Virus to Establish a Sylvatic Transmission Cycle in the Americas.
PLOS Neglected Tropical Diseases, 2016Co-Authors: Benjamin M. Althouse, Nikos Vasilakis, Scott C. Weaver, Mawlouth Diallo, Amadou A. Sall, Kathryn A. HanleyAbstract:Zika virus (ZIKV) originated and continues to circulate in a Sylvatic transmission Cycle between non-human primate hosts and arboreal mosquitoes in tropical Africa. Recently ZIKV invaded the Americas, where it poses a threat to human health, especially to pregnant women and their infants. Here we examine the risk that ZIKV will establish a Sylvatic Cycle in the Americas, focusing on Brazil. We review the natural history of Sylvatic ZIKV and present a mathematical dynamic transmission model to assess the probability of establishment of a Sylvatic ZIKV transmission Cycle in non-human primates and/or other mammals and arboreal mosquito vectors in Brazil. Brazil is home to multiple species of primates and mosquitoes potentially capable of ZIKV transmission, though direct assessment of host competence (ability to mount viremia sufficient to infect a feeding mosquito) and vector competence (ability to become infected with ZIKV and disseminate and transmit upon subsequent feedings) of New World species is lacking. Modeling reveals a high probability of establishment of Sylvatic ZIKV across a large range of biologically plausible parameters. Probability of establishment is dependent on host and vector population sizes, host birthrates, and ZIKV force of infection. Research on the host competence of New World monkeys or other small mammals to ZIKV, on vector competence of New World Aedes, Sabethes, and Haemagogus mosquitoes for ZIKV, and on the geographic range of potential New World hosts and vectors is urgently needed. A Sylvatic Cycle of ZIKV would make future elimination efforts in the Americas practically impossible, and paints a dire picture for the epidemiology of ZIKV and our ability to end the ongoing outbreak of congenital Zika syndrome.
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Potential for Zika virus to establish a Sylvatic transmission Cycle in the Americas
2016Co-Authors: Benjamin M. Althouse, Nikos Vasilakis, Scott C. Weaver, Mawlouth Diallo, Amadou A. Sall, Kathryn A. HanleyAbstract:Zika virus (ZIKV) originated and continues to circulate in a Sylvatic transmission Cycle between non-human primate hosts and arboreal mosquitoes in tropical Africa. Recently ZIKV invaded the Americas, where it poses a threat to human health, especially to pregnant women and their infants. Here we examine the risk that ZIKV will establish a Sylvatic Cycle in the Americas, focusing on Brazil. We review the natural history of Sylvatic ZIKV and present a mathematical dynamic transmission model to assess the probability of establishment of a Sylvatic ZIKV transmission Cycle in non-human primates and/or other mammals and arboreal mosquito vectors in Brazil. Brazil is home to multiple species of primates and mosquitoes potentially capable of ZIKV transmission, though direct assessment of host competence (ability to mount viremia sufficient to infect a feeding mosquito) and vector competence (ability to become infected with ZIKV and disseminate and transmit upon subsequent feedings) of New World species is lacking. Modeling reveals a high probability of establishment of Sylvatic ZIKV across a large range of biologically plausible parameters. Probability of establishment is dependent on host population sizes and birthrates and ZIKV force of infection, but a network of as few as 6,000 primates with 10,000 mosquitoes is capable of supporting establishment of a ZIKV Sylvatic Cycle. Research on the susceptibility of New World monkeys or other small mammals to ZIKV, on the vector competence of New World Aedes, Sabethes, and Haemagogus mosquitoes for ZIKV, and on the geographic range of these species is urgently needed. A Sylvatic Cycle of ZIKV would make future elimination efforts in the Americas practically impossible, and paints a dire situation for the epidemiology of ZIKV and ending the ongoing outbreak of congenital Zika syndrome.
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Infection dynamics of Sylvatic dengue virus in a natural primate host, the African Green Monkey.
The American Journal of Tropical Medicine and Hygiene, 2014Co-Authors: Kathryn A. Hanley, Nikos Vasilakis, Scott C. Weaver, Mathilde Guerbois, Tiffany F. Kautz, Meredith Brown, Stephen S. Whitehead, Preston A. MarxAbstract:The four serotypes of mosquito-borne dengue virus (DENV-1, -2, -3, and -4) that circulate in humans each emerged from an enzootic, Sylvatic Cycle in non-human primates. Herein, we present the first study of Sylvatic DENV infection dynamics in a primate. Three African green monkeys were inoculated with 10 5 plaque-forming units (pfu) DENV-2 strain PM33974 from the Sylvatic Cycle, and one African green monkey was inoculated with 10 5 pfu DENV-2 strain New Guinea C from the human Cycle. All four monkeys seroconverted (more than fourfold rise in 80% plaque reduction neutralization titer (PRNT80)) against the strain of DENV with which they were inoculated; only one (33%) of three monkeys infected with Sylvatic DENV showed a neutralizing antibody response against human-endemic DENV. Virus was detected in two of three monkeys inoculated with Sylvatic DENV at low titer (£ 1.3 log10pfu/mL) and brief duration (£ 2 days). Clinical signs included rash and elevated aspartate aminotransferase (AST) and alanine amino- transferase (ALT) levels.
Livio Heath - One of the best experts on this subject based on the ideXlab platform.
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Investigation of African swine fever outbreaks in pigs outside the controlled areas of South Africa, 2012–2017
Journal of the South African Veterinary Association Tydkrif van die Suid-Afrikaanse Veterinere, 2020Co-Authors: Leana Janse Van Rensburg, Livio Heath, Juanita Van Heerden, Mary-louise Penrith, Thapelo Rametse, Eric M.c. EtterAbstract:South Africa historically experienced sporadic African swine fever (ASF) outbreaks in domestic pigs in the northern parts of the country. This was subsequently indicated to be because of spillover from the Sylvatic Cycle of ASF between warthog and tampans (soft ticks) in the area. South Africa declared this area an ASF-controlled area in 1935, and the area is still controlled in terms of the Animal Diseases Act, 1984 (Act 35 of 1984). Two main epidemics of ASF in domestic pigs were identified outside of the South African ASF-controlled area. The first occurred in 2012 with outbreaks in Gauteng and Mpumalanga provinces, and the second occurred in 2016-2017 with outbreaks in the North West, Free State and Northern Cape provinces. These were the first ASF epidemics in South Africa associated with transmission of the disease via a domestic Cycle. This study found that the spread of ASF in these epidemics was mainly via auctions, swill feeding and scavenging. These three aspects need to be addressed in terms of awareness and education on the disease including implementation of biosecurity measures in order to prevent future ASF outbreaks in South Africa. Specific biosecurity measures should be implemented in the semi-commercial sector to prevent ASF-infected pigs and pig products from being moved to naive pigs and therefore spreading the disease.
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Understanding African swine fever outbreaks in domestic pigs in a Sylvatic endemic area: The case of the South African controlled area between 1977–2017
Transboundary and emerging diseases, 2020Co-Authors: Leana Janse Van Rensburg, M. L. Penrith, E. Etter, Livio Heath, Juanita HeerdenAbstract:South Africa declared a controlled area for African swine fever (ASF) in 1935, consisting of the northern parts of Limpopo, Mpumalanga, North West and Kwa-Zulu Natal Provinces. The area was delineated based on the endemic presence of the Sylvatic Cycle of ASF, involving warthogs and argasid ticks. Occasionally, spillover occurs from the Sylvatic Cycle to domestic pigs, causing ASF outbreaks. In the period 1977 to 2017, 59 outbreaks of ASF were reported in domestic pigs within the ASF controlled area of South Africa. During these outbreaks, at least 4,031 domestic pigs either died or were culled. Season did not affect the number of reported ASF outbreaks, but the number of reported outbreaks in this area per year was thought to be slowly increasing, although not statistically significant. Outbreaks occurred predominantly in Limpopo province (93%) and were mostly due to contact (or suspected contact) with warthog or warthog carcasses. Clustering analysis of outbreaks found that the local municipalities of Ramotshere Moiloa, Lephalale and Thabazimbi had the highest relative risk for outbreaks. In 32 of the 59 outbreaks, the genotype of the ASF virus (ASFV) involved could be determined. Phylogenetic analysis of ASFVs detected in domestic pigs during the study period revealed that p72 genotypes I, III, IV, VII, VIII, XIX, XX, XXI and XXII had been involved in causing outbreaks within the ASF controlled area. No outbreaks were reported in the Kwa-Zulu Natal part of the controlled area during this period. South Africa is unlikely to eradicate all sources of ASFV as spillover from the Sylvatic Cycle in the controlled area continued to occur, but with the implementation of appropriate biosecurity measures pigs can be successfully farmed despite the presence of ASFV in African wild suids and soft ticks.
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genetic characterization of african swine fever virus isolates from soft ticks at the wildlife domestic interface in mozambique and identification of a novel genotype
Transboundary and Emerging Diseases, 2018Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O. p. domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts. (Resume d'auteur)
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Genetic Heterogeneity of African Swine Fever Virus within the Sylvatic Cycle in Central Mozambique
2018Co-Authors: Carlos J. Quembo, Ferran Jori, Livio Heath, Wilna VoslooAbstract:To determine if African swine fever (ASF) is maintained in a Sylvatic Cycle in Mozam-bican wildlife areas, we investigated the presence of soft tick reservoirs of ASFV and their infection rates in the Gorongosa National Park (GNP) and its surrounding villages. The GNP is one of the largest national parks located in the centre of the country. A total of 1,658 soft ticks were recovered from warthog burrows and pig-pens at the wildlife/livestock interface and viral DNA was detected by nested PCR in 19 % of Ornithodoros porcinus porcinus and 15 % of O. p. domesticus. Isola-tion of the virus was successful in approximately 50 % of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial gene sequencing (p72, p30 and p54) and analysis of the cen-tral variable region (CVR) of the B602L gene. Eleven isolates clustered in genotype II and were homologous to contemporary isolates from southern Africa, the Indian Ocean and Eastern Europe. Three isolates grouped within genotype V were simi-lar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated as genotype XXIV. The isolates classified within genotypes II and XXIV clustered into three major sub-types based on their p30 and p54 sequences. Based on analysis of the CVR gene, the viruses were classified into eight subgroups. This work corroborates for the first time the wildlife origin of Genotype II and confirms that a large diversity of ASFV strains maintained in wildlife areas can act as a permanent source of virus for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Eastern Europe suggests that the African Sylvatic Cycle has a high potential to disseminate different ASFV into new geographic areas and justifies the need to continue studying the epidemiology and ecology of ASF Sylvatic hosts in sub-Saharan Africa.
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Genetic characterization of African swine fever virus isolates from soft ticks at the wildlife/domestic interface in Mozambique and identification of a novel genotype
Transboundary and emerging diseases, 2018Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O.p.domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts.
Ferran Jori - One of the best experts on this subject based on the ideXlab platform.
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African Swine Fever Epidemiology and Control
Annual Review of Animal Biosciences, 2020Co-Authors: Linda K. Dixon, Karl Ståhl, Ferran Jori, Laurence Vial, Dirk U. PfeifferAbstract:African swine fever is a devastating disease that can result in death in almost all infected pigs. The continuing spread of African swine fever from Africa to Europe and recently to the high-pig production countries of China and others in Southeast Asia threatens global pork production and food security. The African swine fever virus is an unusual complex DNA virus and is not related to other viruses. This has presented challenges for vaccine development, and currently none is available. The virus is extremely well adapted to replicate in its hosts in the Sylvatic Cycle in East and South Africa. Its spread to other regions, with different wildlife hosts, climatic conditions, and pig production systems, has revealed unexpected epidemiological scenarios and different challenges for control. Here we review the epidemiology of African swine fever in these different scenarios and methods used for control. We also discuss progress toward vaccine development and research priorities to better understand this complex disease and improve control.
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genetic characterization of african swine fever virus isolates from soft ticks at the wildlife domestic interface in mozambique and identification of a novel genotype
Transboundary and Emerging Diseases, 2018Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O. p. domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts. (Resume d'auteur)
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Genetic Heterogeneity of African Swine Fever Virus within the Sylvatic Cycle in Central Mozambique
2018Co-Authors: Carlos J. Quembo, Ferran Jori, Livio Heath, Wilna VoslooAbstract:To determine if African swine fever (ASF) is maintained in a Sylvatic Cycle in Mozam-bican wildlife areas, we investigated the presence of soft tick reservoirs of ASFV and their infection rates in the Gorongosa National Park (GNP) and its surrounding villages. The GNP is one of the largest national parks located in the centre of the country. A total of 1,658 soft ticks were recovered from warthog burrows and pig-pens at the wildlife/livestock interface and viral DNA was detected by nested PCR in 19 % of Ornithodoros porcinus porcinus and 15 % of O. p. domesticus. Isola-tion of the virus was successful in approximately 50 % of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial gene sequencing (p72, p30 and p54) and analysis of the cen-tral variable region (CVR) of the B602L gene. Eleven isolates clustered in genotype II and were homologous to contemporary isolates from southern Africa, the Indian Ocean and Eastern Europe. Three isolates grouped within genotype V were simi-lar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated as genotype XXIV. The isolates classified within genotypes II and XXIV clustered into three major sub-types based on their p30 and p54 sequences. Based on analysis of the CVR gene, the viruses were classified into eight subgroups. This work corroborates for the first time the wildlife origin of Genotype II and confirms that a large diversity of ASFV strains maintained in wildlife areas can act as a permanent source of virus for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Eastern Europe suggests that the African Sylvatic Cycle has a high potential to disseminate different ASFV into new geographic areas and justifies the need to continue studying the epidemiology and ecology of ASF Sylvatic hosts in sub-Saharan Africa.
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Genetic characterization of African swine fever virus isolates from soft ticks at the wildlife/domestic interface in Mozambique and identification of a novel genotype
Transboundary and emerging diseases, 2018Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O.p.domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts.
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Genetic characterization of African swine fever virus isolates from soft ticks at the wildlife/domestic interface in Mozambique and identification of a novel genotype
Transboundary and Emerging Diseases, 2017Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O. p. domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts. (Resume d'auteur)
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genetic characterization of african swine fever virus isolates from soft ticks at the wildlife domestic interface in mozambique and identification of a novel genotype
Transboundary and Emerging Diseases, 2018Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O. p. domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts. (Resume d'auteur)
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Genetic Heterogeneity of African Swine Fever Virus within the Sylvatic Cycle in Central Mozambique
2018Co-Authors: Carlos J. Quembo, Ferran Jori, Livio Heath, Wilna VoslooAbstract:To determine if African swine fever (ASF) is maintained in a Sylvatic Cycle in Mozam-bican wildlife areas, we investigated the presence of soft tick reservoirs of ASFV and their infection rates in the Gorongosa National Park (GNP) and its surrounding villages. The GNP is one of the largest national parks located in the centre of the country. A total of 1,658 soft ticks were recovered from warthog burrows and pig-pens at the wildlife/livestock interface and viral DNA was detected by nested PCR in 19 % of Ornithodoros porcinus porcinus and 15 % of O. p. domesticus. Isola-tion of the virus was successful in approximately 50 % of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial gene sequencing (p72, p30 and p54) and analysis of the cen-tral variable region (CVR) of the B602L gene. Eleven isolates clustered in genotype II and were homologous to contemporary isolates from southern Africa, the Indian Ocean and Eastern Europe. Three isolates grouped within genotype V were simi-lar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated as genotype XXIV. The isolates classified within genotypes II and XXIV clustered into three major sub-types based on their p30 and p54 sequences. Based on analysis of the CVR gene, the viruses were classified into eight subgroups. This work corroborates for the first time the wildlife origin of Genotype II and confirms that a large diversity of ASFV strains maintained in wildlife areas can act as a permanent source of virus for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Eastern Europe suggests that the African Sylvatic Cycle has a high potential to disseminate different ASFV into new geographic areas and justifies the need to continue studying the epidemiology and ecology of ASF Sylvatic hosts in sub-Saharan Africa.
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Genetic characterization of African swine fever virus isolates from soft ticks at the wildlife/domestic interface in Mozambique and identification of a novel genotype
Transboundary and emerging diseases, 2018Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O.p.domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts.
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Genetic characterization of African swine fever virus isolates from soft ticks at the wildlife/domestic interface in Mozambique and identification of a novel genotype
Transboundary and Emerging Diseases, 2017Co-Authors: Carlos J. Quembo, Ferran Jori, Wilna Vosloo, Livio HeathAbstract:African swine fever virus (ASFV) is one of the most threatening infectious diseases of pigs. There are not sufficient data to indicate the importance of the Sylvatic Cycle in the spread and maintenance of the disease locally and potentially, globally. To assess the capacity to maintain ASF in the environment, we investigated the presence of soft tickreservoirs of ASFV in Gorongosa National Park (GNP) and its surrounding villages. A total of 1,658 soft ticks were recovered from warthog burrows and pig pens at the wildlife/livestock interface of the GNP and viral DNA was confirmed by nested PCR in 19% of Ornithodoros porcinus porcinus and 15% of O. p. domesticus. However, isolation of ASFV was only achieved in approximately 50% of the PCR-positive samples with nineteen haemadsorbing virus isolates recovered. These were genotyped using a combination of partial sequencing of the B646L gene (p72) and analysis of the central variable region (CVR) of the B602L gene. Eleven isolates were classified as belonging to genotype II and homologous to contemporary isolates from southern Africa, the Indian Ocean and eastern Europe. Three isolates grouped within genotype V and were similar to previous isolates from Mozambique and Malawi. The remaining five isolates constituted a new, previously unidentified genotype, designated genotype XXIV. This work confirms for the first time that the virus currently circulating in eastern Europe is likely to have a wildlife origin, and that the large diversity of ASFV maintained in wildlife areas can act as a permanent sources of different strains for the domestic pig value chain in Mozambique and beyond its boundaries. Their genetic similarity to ASFV strains currently spreading across Europe justifies the need to continue studying the Sylvatic Cycle in this African country and other parts of southern Africa in order to identify potential hot spots of ASF emergence and target surveillance and control efforts. (Resume d'auteur)
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Investigation into the Epidemiology of African Swine Fever Virus at the Wildlife – Domestic Interface of the Gorongosa National Park, Central Mozambique
Transboundary and Emerging Diseases, 2014Co-Authors: Carlos J. Quembo, Ferran Jori, Livio Heath, Ricardo Pérez-sánchez, Wilna VoslooAbstract:An epidemiological study of African swine fever (ASF) was conducted between March 2006 and September 2007 in a rural area adjacent to the Gorongosa National park (GNP) located in the Central Mozambique. Domestic pigs and warthogs were sampled to determine the prevalence of antibodies against ASF virus and the salivary antigens of Ornithodoros spp. ticks, while ticks collected from pig pens were tested for the presence of ASFV. In addition, 310 framers were interviewed to gain a better understanding of the pig value chain and potential practices that could impact on the spread of the virus. The sero-prevalence to ASFV was 12.6% on farms and 9.1% in pigs, while it reached 75% in warthogs. Approximately 33% of pigs and 78% of warthogs showed antibodies against salivary antigens of ticks. The differences in sero-prevalence between farms close to the GNP, where there is greater chance for the Sylvatic Cycle to cause outbreaks, and farms located in the rest of the district, where pig to pig transmission is more likely to occur, were marginally significant. Ornithodoros spp. ticks were found in only 2 of 20 pig pens outside the GNP, and both pens had ticks testing positive for ASFV DNA. Interviews carried out among farmers indicated that biosecurity measures were mostly absent. Herd sizes were small with pigs kept in a free-ranging husbandry system (65%). Only 1.6% of farmers slaughtered on their premises, but 51% acknowledged allowing visitors into their farms to purchase pigs. ASF outbreaks seemed to have a severe economic impact with nearly 36% of farmers ceasing pig farming for at least 1 year after a suspected ASF outbreak. This study provides the first evidence of the existence of a Sylvatic Cycle in Mozambique and confirms the presence of a permanent source of virus for the domestic pig value chain.
