Abstract:
African swine fever (ASF) is an economically significant haemorrhagic disease of domestic
pigs. It is caused by the African swine fever virus (ASFV), a deoxyribonucleic acid (DNA)
arbovirus. Argasid ticks of the genus Ornithodoros, which are widely distributed throughout
southern Africa, play a primary role in virus maintenance and spread within the endemic
sylvatic cycle. The ASF status of Swaziland is unknown, but this land-locked country is
surrounded by ASF-positive countries, has a burgeoning pig industry and sylvatic cycle hosts
present within its borders. In this first assessment of ASF status, warthog burrows in seven
nature reserves and game management areas in Swaziland were investigated for tick and
virus presence. Tick infestation rates of between 33.3% – 88.8% were recovered for the four
Ornithodoros-infested reserves. A total of 562 ticks were screened for virus genome presence
using a duplex Polymerase Chain Reaction (PCR) that targets the C-terminal end of the p72
gene of the ASFV and confirms DNA integrity through amplification of the 16S rRNA tick
host gene. All samples were negative for virus genome presence and positive for the tick
genome target. Nucleotide sequencing of the latter confirmed that Ornithodoros ticks from
Swaziland are identical to those from the Kruger National Park in South Africa across the
gene region characterised. Whilst this first evaluation of ASF presence in Swaziland indicates
that the virus does not appear to be present in the key virus vector, the presence of sylvatic
cycle hosts, together with the country’s proximity to ASF-affected countries calls for expanded
investigations and regular monitoring of the ASF status of Swaziland.
