Swine Virology and Immunology Unit, Laboratoire de Ploufragan-Plouzané-Niort, Agence Nationale de Sécurité Sanitaire (ANSES), Ploufragan, France.
UMR ASTRE Animal Santé, Territoires, Risques et Ecosystèmes, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Montpellier, France.
PLoS One. 2019 Nov 27;14(11):e0225657. doi: 10.1371/journal.pone.0225657. eCollection 2019.
African swine fever (ASF) is a lethal hemorrhagic disease in domestic pigs and wild suids caused by African swine fever virus (ASFV), which threatens the swine industry globally. In its native African enzootic foci, ASFV is naturally circulating between soft ticks of the genus Ornithodoros, especially in the O. moubata group, and wild reservoir suids, such as warthogs (Phacochoerus spp.) that are bitten by infected soft ticks inhabiting their burrows. While the ability of some Afrotropical soft ticks to transmit and maintain ASFV is well established, the vector status of Palearctic soft tick species for ASFV strains currently circulating in Eurasia remains largely unknown. For example, the Iberian soft tick O. erraticus is a known vector and reservoir of ASFV, but its ability to transmit different ASFV strains has not been assessed since ASF re-emerged in Europe in 2007. Little is known about vector competence for ASFV in other species, such as O. verrucosus, which occurs in southern parts of Eastern Europe, including Ukraine and parts of Russia, and in the Caucasus. Therefore, we conducted transmission trials with two Palearctic soft tick species, O. erraticus and O. verrucosus, and the Afrotropical species O. moubata. We tested the ability of ticks to transmit virulent ASFV strains, including one of direct African origin (Liv13/33), and three from Eurasia that had been 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 failed to 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. Additionally, the persistence of infection in soft ticks for several months reaffirms that the infectious status of a given tick species is only part of the data required to assess its vector competence for ASFV.
非洲猪瘟（ASF）是一种致命的出血性疾病，可感染家猪和野猪，由非洲猪瘟病毒（ASFV）引起，该病毒对全球的养猪业构成威胁。在其自然流行的非洲地方性疫源地，ASFV 在软蜱属的软蜱中自然循环，尤其是在 O. moubata 组中，并且在野生储藏野猪中循环，这些野猪被栖息在其洞穴中的感染软蜱叮咬。虽然一些非洲热带软蜱传播和维持 ASFV 的能力已经得到充分证实，但目前在欧亚大陆流行的 ASFV 毒株的古北软蜱物种的媒介地位在很大程度上仍然未知。例如，伊比利亚软蜱 O. erraticus 是 ASFV 的已知传播媒介和储藏宿主，但自 2007 年 ASF 在欧洲再次出现以来，尚未评估其传播不同 ASFV 毒株的能力。对于其他物种（如 O. verrucosus）的 ASFV 媒介能力知之甚少，O. verrucosus 分布于东欧的南部地区，包括乌克兰和俄罗斯的部分地区以及高加索地区。因此，我们进行了两种古北软蜱物种（O. erraticus 和 O. verrucosus）和一种非洲热带物种（O. moubata）的传播试验。我们测试了蜱传播强毒 ASFV 毒株的能力，包括一种直接来自非洲的毒株（Liv13/33），以及三种来自欧亚大陆的毒株，这些毒株曾参与过先前的（OurT88/1）和当前的（格鲁吉亚 2007/1 和 Ukr12/Zapo）疫病。我们的实验结果表明，O. moubata 能够传播非洲和欧亚 ASF 毒株，而 O. erraticus 和 O. verrucosus 未能传播欧亚 ASF 毒株。然而，当用感染了病毒血症猪的 O. erraticus 和 O. verrucosus 叮咬的粉碎蜱的匀浆接种时，未感染的猪表现出 ASF 的临床症状，这证明了蜱中存在的 ASFV 的传染性。这些结果证明，O. erraticus 和 O. verrucosus 不太可能成为欧亚大陆目前流行的 ASFV 毒株的传播媒介。此外，软蜱可在几个月内持续感染，这再次证实了给定蜱种的感染状态仅是评估其 ASFV 媒介能力所需数据的一部分。
