Background: African 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.
Results: Two 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.
Conclusion: The 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.
Thomas, L.F., Bishop, R.P., Onzere, C., Mcintosh, M.T., Lemire, K.A., Glanville, W.A. de, Cook, E.A.J. and Fèvre, E.M. 2016. Evidence for the presence of African swine fever virus in an endemic region of Western Kenya in the absence of any reported outbreak. BMC Veterinary Research 12: 192.