Do wild suids from Ndumo Game Reserve, South Africa, play a role in the maintenance and transmission of African Swine Fever to domestic pigs?

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.