Biosciences eastern and central Africa - International Livestock Research Institute Hub, Nairobi, Kenya.
Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania.
Transbound Emerg Dis. 2021 Mar;68(2):813-823. doi: 10.1111/tbed.13747. Epub 2020 Aug 15.
African swine fever (ASF) is a severe haemorrhagic disease of domestic pigs caused by ASF virus (ASFV). ASFV is transmitted by soft ticks (Ornithodoros moubata complex group) and by direct transmission. In Africa, ASF is maintained in transmission cycles of asymptomatic infection involving wild suids, mainly warthogs (Phacochoerus africanus). ASF outbreaks have been reported in many parts of Tanzania; however, active surveillance has been limited to pig farms in a few geographical locations. There is an information gap on whether and where the sylvatic cycle may occur independently of domestic pigs. To explore the existence of a sylvatic cycle in Saadani National Park in Tanzania, blood and serum samples were collected from 19 warthogs selected using convenience sampling along vehicle-accessible transects within the national park. The ticks were sampled from warthog burrows. Blood samples and ticks were subjected to ASFV molecular diagnosis (PCR) and genotyping, and warthog sera were subjected to serological (indirect ELISA) testing for ASFV antibody detection. All warthog blood samples were PCR-negative, but 16/19 (84%) of the warthog sera were seropositive by ELISA confirming exposure of warthogs to ASFV. Of the ticks sampled, 20/111 (18%) were positive for ASFV by conventional PCR. Sequencing of the p72 virus gene fragments showed that ASF viruses detected in ticks belonged to genotype XV. The results confirm the existence of a sylvatic cycle of ASFV in Saadani National Park, Tanzania, that involves ticks and warthogs independent of domestic pigs. Our findings suggest that genotype XV previously reported in 2008 in Tanzania is likely to be widely distributed and involved in both wild and domestic infection cycles. Whole-genome sequencing and analysis of the ASFV genotype XV circulating in Tanzania is recommended to determine the phylogeny of the viruses.
非洲猪瘟（ASF）是一种由 ASF 病毒（ASFV）引起的家猪严重出血性疾病。ASFV 通过软蜱（Ornithodoros moubata 复合组）和直接传播传播。在非洲，ASF 维持在涉及野猪的无症状感染的传播循环中，主要是疣猪（Phacochoerus africanus）。坦桑尼亚许多地区都报告了 ASF 暴发；然而，主动监测仅限于少数地理位置的养猪场。关于是否以及在何处可能发生与家猪无关的森林循环，存在信息差距。为了探索坦桑尼亚萨达尼国家公园是否存在森林循环，使用便利抽样法从公园内车辆可达的横截线上选择了 19 头疣猪，采集了血液和血清样本。从疣猪洞穴中采集了蜱虫。对血液样本和蜱虫进行了 ASFV 分子诊断（PCR）和基因分型，对疣猪血清进行了血清学（间接 ELISA）检测以检测 ASFV 抗体。所有疣猪血液样本的 PCR 均为阴性，但 19 份血清样本中的 16 份（84%）通过 ELISA 呈血清阳性，证实疣猪接触过 ASFV。在采集的蜱虫中，通过常规 PCR 有 20/111（18%）为 ASFV 阳性。对 p72 病毒基因片段的测序表明，在蜱虫中检测到的 ASF 病毒属于基因型 XV。研究结果证实，坦桑尼亚萨达尼国家公园存在涉及蜱虫和疣猪的 ASFV 森林循环，与家猪无关。我们的研究结果表明，2008 年在坦桑尼亚报告的基因型 XV 可能广泛分布并参与野生和家养感染循环。建议对坦桑尼亚循环的 ASFV 基因型 XV 进行全基因组测序和分析，以确定病毒的系统发育。
