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

Abstract

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.

First detection of African swine fever (ASF) virus genotype X and serogroup 7 in symptomatic pigs in the Democratic Republic of Congo

“…The number of TRS repeat observed is relatively small compared to reports from some studies in the same geographic region describing the TRS motif repeated over 20 to 50 times [34,42]. However, Mulumba-Mfumu et al also observed this sequence repeated only 5 or 6 times in some DR Congo isolates [20]. The two CVR variants found in our study were different from the previously reported variants in DR Congo ASFV isolates [36] and to any other known viruses causing outbreaks or ASF cases, thus suggesting that the ASFV genotype 10 in circulation in the South Kivu province of DR Congo identified in this study may be unique [41,43].…”

“…African swine fever constitutes the major obstacle to the development of the pig industry in the DRC, with sporadic outbreaks occurring across various areas throughout the year [20]. Despite recurrent occurrence of suspected ASF outbreaks in South Kivu province, information on the virus characterization remains scarce.…”

“…Five separate PCR experiments were set up to amplify PPA-positive samples: (i) for p72 genotype classification, the C-terminal region of the p72 protein gene was amplified using the primers p72-U/D [14]; (ii) for p54 genotyping, the gene E183L encoding the p54 protein was amplified using the primers PPA722/PPA89 [10]; (iii) the B602L gene characterized by the Central Variable Region (CVR) was amplified using the primer pairs CVR-FL1 and CVR-FL2 as previously reported [20]; (iv) for determining the origin, and to distinguish between closely related ASFV isolates circulating in the South Kivu province, a 356 bp fragment, specific for identification of Tandem Repeat Sequences (TRS), located between the I73R and I329L genes was amplified using the primer pairs ECO1A and ECO1B [30]; (v) to determine the serogroups of the isolates, the partial EP402R gene encoding the CD2v protein [23] was amplified and sequenced using two sets of primers to generate two overlapping fragments. The primers used for the diagnosis and genotyping are presented in the Table 1. PCR amplicons were confirmed using 2% agarose gel electrophoresis in the presence of molecular weight markers.…”

“…African countries with the highest number of outbreaks (84) registered in the Democratic Republic of Congo (DRC) causing a loss of 105,614 pigs [19,20]. Previous studies have reported circulation of genotype I, IX and XIV in DRC, encouraging the need for continued characterization of ASFV isolates responsible for outbreaks to better understand the spread of this economical important disease in DRC.…”

Genetic profile of African swine fever virus responsible for the 2019 outbreak in northern Malawi

“…Recently, an additional epidemiological cycle characterized by both direct transmission between infected and susceptible Eurasian wild boar (Sus scrofa) and indirect transmission through carcasses in the habitat has been described and named the wild boarhabitat cycle (8). The current geographical distribution of ASF extends across more than 50 countries in Africa, Europe and Asia and among them, 33 are countries in Africa, south of Sahara (9,10). The recent spread of ASF within Europe and Asia has substantially increased the global concern regarding the disease and it is considered as the most devastating disease to global domestic pig industry and food security (2).…”