Do wild suids from Ndumo Game Reserve, South Africa, play a role in the
maintenance and transmission of African Swine Fever to domestic pigs?
Abstract
In Southern Africa, the African Swine Fever (ASF) sylvatic cycle
presents a permanent threat for the development of the pig farming
industry. Warthogs (Phacochoerus africanus) and bushpigs (Potamochoerus
larvatus), wild reservoirs of ASF are present in Ndumo Game Reserve
(NGR), located in Northern KwaZulu Natal Province in South Africa and
within 30 km of the locations of endemic ASF outbreaks in Mozambique
where sylvatic disease transmission has been implicated. To assess if
wild suids represent a risk of ASF virus spillover to domestic pigs in
the neighbouring community, transect counts and fence patrols were
conducted and camera traps were deployed in NGR to estimate wild suid
abundance and incursions outside NGR boundaries. We searched for
Ornithodoros ticks in 35 warthog burrows distributed across different
NGR areas. Pig farmers (n=254) surrounding Mathenjwa Community were
interviewed to gather information on interactions between domestic and
wild suids and the occurrence of ASF. We conclude that NGR has
established populations of bushpigs and warthogs, estimated at 5 and 3-5
individuals/km2 respectively. Both species move out of the reserve
regularly (15.4 warthogs/day and 6.35 bushpigs/day), with a significant
increase of movements during the dry season. Some farmers observed
warthogs and bushpigs as far as 8 and 19 km from the reserve
respectively, but no direct wild-domestic suids interactions nor any ASF
outbreaks were reported. In addition, no soft ticks were found among the
35 warthog burrows. The absence of ticks in warthog burrows from NGR and
the absence of reported outbreaks and familiarity with ASF in the
surrounding farming area, suggest that a sylvatic cycle of ASF is at
present unlikely in NGR. However, further research should be undertaken
to confirm this by surveying a larger number of warthog burrows and
monitoring potential antibodies in warthogs from NGR and domestic pigs
in the neighbouring community.