Evidence for the presence of African swine fever virus in an endemic region of Western Kenya in the absence of any reported outbreak

Abstract

BackgroundAfrican swine fever (ASF), caused by African swine fever virus (ASFV), is a severe haemorrhagic disease of pigs, outbreaks of which can have a devastating impact upon commercial and small-holder pig production. Pig production in western Kenya is characterised by low-input, free-range systems practised by poor farmers keeping between two and ten pigs. These farmers are particularly vulnerable to the catastrophic loss of livestock assets experienced in an ASF outbreak. This study wished to expand our understanding of ASFV epidemiology during a period when no outbreaks were reported.ResultsTwo hundred and seventy six whole blood samples were analysed using two independent conventional and real time PCR assays to detect ASFV. Despite no recorded outbreak of clinical ASF during this time, virus was detected in 90/277 samples analysed by conventional PCR and 142/209 samples analysed by qPCR. Genotyping of a sub-set of these samples indicated that the viruses associated with the positive samples were classified within genotype IX and that these strains were therefore genetically similar to the virus associated with the 2006/2007 ASF outbreaks in Kenya.ConclusionThe detection of ASFV viral DNA in a relatively high number of pigs delivered for slaughter during a period with no reported outbreaks provides support for two hypotheses, which are not mutually exclusive: (1) that virus prevalence may be over-estimated by slaughter-slab sampling, relative to that prevailing in the wider pig population; (2) that sub-clinical, chronically infected or recovered pigs may be responsible for persistence of the virus in endemic areas.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0830-5) contains supplementary material, which is available to authorized users.

Evidence of African Swine Fever Virus in Pigs Slaughtered at Muhanzi Municipal Abattoir in Bukavu City, Eastern of Democratic Republic of Congo

“…Additionally the higher prevalence of ASFV obtained in our study compared to studies conducted in farm level [20] may be due to the fact that farmers probably recognize ASF symptoms at an early stage and rapidly bring animals to the slaughter house for sale [21]. This evidence was supported by a considerably higher ASFV prevalence found in apparently healthy animals sampled at slaughterhouse, than in the farm pig population [22].…”

Current status and evolving approaches to African swine fever vaccine development

“…Additionally, soft ticks can be persistently infected and contribute to the dissemination of ASFV as a vector (Tulman et al, 2009). Thus, ASF has a complex epidemiology (Arias, Jurado, Gallardo, Fernández-Pinero, & Sánchez-Vizcaíno, 2018;Sánchez-Vizcaíno, Mur, Bastos, & Pernith, 2015;Thomas et al, 2016) and continues to be a challenging disease (Arias et al, 2018;Sánchez-Cordón, Montoya, Reis, & Dixon, 2018). There is an immediate and pressing need to develop a safe and effective vaccine and alleviate significant economic losses to the pig industry.…”

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

“…The discovery of a cycle of maintenance and transmission of ASFV between domestic pigs and O. moubata complex ticks in the Mchinji district in Malawi revealed a pig population with improved resistance to the pathogenic effects of ASFV and the ability of the disease to persist without involvement of wild suids (Haresnape & Mamu, 1986;Haresnape et al, 1985Haresnape et al, , 1987. Similarly resistant populations of domestic pigs have been reported in Kenya (Okoth et al, 2012), along the Kenya/Uganda border on both sides (Abworo et al, 2017;Thomas et al, 2016); Mozambique (Penrith et al, 2007;Pen-rith, Thomson, Bastos, Phiri, et al, 2004) and the Eastern Province of Zambia (Simulundu et al, 2017). The involvement of ticks in these populations has not been documented and requires further investigation.…”