Investigation into the Epidemiology of African Swine Fever Virus at the Wildlife - Domestic Interface of the Gorongosa National Park, Central Mozambique

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212

SummaryAfrican 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.

Section: Discussionmentioning

confidence: 99%

Genetic characterization of African swine fever virus isolates from soft ticks at the wildlife/domestic interface in Mozambique and identification of a novel genotype

Quembo

Jori

Vosloo

et al. 2017

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“…A higher infection rate was recently reported for ticks from warthog burrows in the Gorongosa National Park in Mozambique, where 19% of the sample was positive for ASFV genome by nested PCR, although virus was isolated from only a little under half of the PCR positive samples (Quembo, Jori, Vosloo, & Heath, ). Interestingly, 75% of the warthogs sampled in the same study were positive for antibodies to ASFV, but this may be attributable to the small sample size ( n = 12) (Quembo, Jori, Heath, Pérez‐Sánchez, & Vosloo, ). Warthog infection rates in areas where the sylvatic cycle is present are usually close to 100%, although lower rates (50%–90% in Uganda and 75% in Gorongosa National Park, Mozambique) have been reported (Plowright et al., ; Quembo et al., ).…”

Section: Transmission Routes Of Asfv In Sylvatic Cyclesmentioning

confidence: 98%

“…Interestingly, 75% of the warthogs sampled in the same study were positive for antibodies to ASFV, but this may be attributable to the small sample size ( n = 12) (Quembo, Jori, Heath, Pérez‐Sánchez, & Vosloo, ). Warthog infection rates in areas where the sylvatic cycle is present are usually close to 100%, although lower rates (50%–90% in Uganda and 75% in Gorongosa National Park, Mozambique) have been reported (Plowright et al., ; Quembo et al., ). Only 2.5% of warthogs sampled in the Mkuze National Park in Northern Kwazulu‐Natal, South Africa, were reported positive for antibodies to ASFV, accompanied by a very low infection rate (0.06%) in Ornithodoros sampled from warthog burrows in the same area (Thomson, ; Thomson et al., ).…”

Section: Transmission Routes Of Asfv In Sylvatic Cyclesmentioning

confidence: 98%

Epidemiology of African swine fever in Africa today: Sylvatic cycle versus socio‐economic imperatives

Penrith

Bastos

Etter

et al. 2019

101

119

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.

“…Kenya, Malawi, Mozambique, Tanzania, Uganda and Zambia have experienced multiple to frequent outbreaks (Table ). The endemic occurrence of ASF in domestic pigs has subsequently been documented in several Eastern African countries: Kenya (Gallardo, Ademun, et al, ; Gallardo, Okoth, et al, ; Lichoti et al, ; Okoth et al, ), Madagascar (Randrianantoandro, Kono, & Kubota, ; Ravaomanana et al, , ; Roger, Ratovonjato, Vola, & Uilenberg, ), Malawi (Haresnape, Lungu, & Mamu, , ); Mozambique (Penrith et al, , ; Quembo et al, ), Tanzania (Misinzo et al, ; Wambura, Masambu, & Msami, ), Uganda (Atuhaire, Afayoa, Ochwo, Mwesigwa, Okuni, et al, ; Barongo et al, ; Gallardo, Ademun, et al, ; Muhangi et al, ; Muwonge et al., ) and the Eastern Province of Zambia (Samui, Mwanaumo, & Chizyuka, ; Samui et al, ; Simulundu et al, , ; Wilkinson et al, ).…”

Section: History Current Status Transmission Cycles Recent Outbreamentioning

confidence: 99%

“…On the contrary, the disease has devastating socio‐economic consequences in domestic pigs due to its high lethality. A domestic pig–tick cycle between domestic pigs and Ornithodoros ticks that live in their shelters (pig–tick cycle) has been demonstrated in Malawi and Mozambique and may be more widespread (Haresnape, Lungu, & Mamu, , ; Quembo, Jori, Heath, Pérez‐Sánchez, & Vosloo, ; Simulundu et al, ; Wilkinson, Pegram, Berry, Lemche, & Schels, ). A domestic cycle dependent on direct or indirect transmission amongst domestic pig populations without involvement of wild hosts or vectors occurs throughout the region.…”

Section: Introductionmentioning

confidence: 99%

African swine fever: Update on Eastern, Central and Southern Africa

Mulumba‐Mfumu

Saegerman

Dixon

et al. 2019

Control of African swine fever (ASF) in countries in Eastern, Central and SouthernAfrica (ECSA) is particularly complex owing to the presence of all three known epidemiological cycles of maintenance of the virus, namely an ancient sylvatic cycle involving the natural hosts and vectors of the disease as well as domestic cycles with and without involvement of natural vectors. While the situation is well documented in some of the countries, for others very little information is available. In spite of the unfavourable ASF situation, the pig population in the sub-region has grown exponentially in recent decades and is likely to continue to grow in response to rapid urban growth resulting in increasing demand for animal protein by populations that are no longer engaged in livestock production. Better management of ASF will be essential to permit the pig sector to reach its full potential as a supplier of high quality protein and a source of income to improve livelihoods and create wealth. No vaccine is currently available and it is likely that, in the near future, the sub-region will continue to rely on the implementation of preventive measures, based on the epidemiology of the disease, to avoid both the devastating losses that outbreaks can cause and the risk the sub-region poses to other parts of Africa and the world. The current situation in the ECSA sub-region is reviewed and gaps in knowledge are identified in order to support ongoing strategy development for managing ASF in endemic areas.