Comparative vector competence of the Afrotropical soft tick Ornithodoros moubata and Palearctic species, O. erraticus and O. verrucosus, for African Swine Fever virus strains circulating in Eurasia

African swine fever (ASF) is a lethal hemorrhagic fever disease in domestic pigs and wild boars caused by African swine fever virus (ASFV), which threatens the swine industry. In its native African endemic area, ASFV is naturally circulating between soft ticks of the genus Ornithodoros, especially in the O. moubata complex, and wild reservoir suids that are bitten by infected soft ticks inhabiting the same burrows. While the ability of some Afrotropical soft ticks to transmit and maintain ASFV is established, the vector status of Palearctic soft ticks remains unknown for ASFV strains currently circulating in Eurasia. The Iberian O. erraticus is a known vector and reservoir of ASFV, but ASFV re-emerged in Europe after eradication resulting in the circulation of new ASFV strains that have been spreading westward since 2007. Therefore, we conducted transmission trials with the Palearctic soft tick species O. erraticus and O. verrucosus, and the Afrotropical O. moubata, that fed on viremic pigs infected with highly virulent ASFV strains including one directly from Africa (Liv13/33), and three from Eurasia involved in previous (OurT88/1), and the current epizooties (Georgia2007/1, and Ukr12/Zapo). Our experimental results showed that O. moubata was able to transmit the African and Eurasian ASFV strains, whereas O. erraticus and O. verrucosus did not transmit the Eurasian ASFV strains. However, naïve pigs showed clinical signs of ASF when inoculated with homogenates of crushed O. erraticus and O. verrucosus ticks that fed on viraemic pigs, which proved the infectiousness of ASFV contained in the ticks. These results documented that O. erraticus and O. verrucosus are unlikely to be capable vectors of ASFV strains currently circulating in Eurasia. Persistent infection for several months reaffirms that the infectious status of a soft tick species is only part of the data required to assess its vector competence for ASFV.