Detection of African Swine Fever Virus in Tick Species Associated with Indigenous and Extralimital Warthog Populations in South Africa.

We investigated the possibility that sylvatic circulation of African swine fever virus (ASFV) in warthogs and ticks had extended beyond the historically affected northern part of South Africa that was declared a controlled area in 1935 to prevent the spread of infection to the rest of the country. We recently reported finding antibody to the virus in extralimital warthogs in the south of the country, and now describe the detection of infected ticks outside the controlled area. A total of 5078 ticks was collected at 45 locations in 7/9 provinces during 2019-2021 and assayed as 711 pools for virus content by qPCR, while 221 pools were also analysed for tick phylogenetics. Viral nucleic acid was detected in 50 tick pools representing all four members of the complex known to occur in South Africa: and species yielded ASFV genotypes XX, XXI, XXII at 4 locations and yielded ASFV genotype I at two locations inside the controlled area. Outside the controlled area, and ticks yielded ASFV genotype I at 7 locations, while genotype III ASFV was identified in ticks at a single location. Two of the three species of the complex ticks known to be present in the country, and , were collected at single locations and found negative for virus. The only member of the subgenus of ticks known to occur in South Africa, , was collected from warthog burrows for the first time, in Addo National Park in the Eastern Cape Province where ASFV had never been recorded, and it tested negative for the viral nucleic acid. While it is confirmed that there is sylvatic circulation of ASFV outside the controlled area in South Africa, there is a need for more extensive surveillance and for vector competence studies with various species of ticks.