Faculty of Health Sciences and Veterinary Medicine, School of Veterinary Medicine, Neudamm Campus, University of Namibia, Private Bag 13301, Windhoek 9000, Namibia.
Central Veterinary Laboratory (CVL), 24 Goethe Street, Private Bag 18137, Windhoek 9000, Namibia; Faculty of Veterinary Medicine, University of Teramo, Teramo 64100, Italy.
Acta Trop. 2024 Jan;249:107085. doi: 10.1016/j.actatropica.2023.107085. Epub 2023 Nov 26.
Since its first identification in 2015, porcine circovirus 3 (PCV-3) has been reported worldwide with a high frequency and in the presence of several clinical conditions, although its impact on pig health and productivity is still debated. Data on the presence of PCV-3 in Africa are, however, limited. A previous study performed on commercial pigs in Namibia failed to identify the pathogen. In the present study, the viral circulation in backyard farms, characterised by lower biosecurity measures and frequent animal exchange between farms, was assessed. The susceptibility of warthogs to PCV-3 infection and their potential epidemiological role were also evaluated. Tonsils from 77 pigs from backyard piggeries and 55 warthogs were collected in different regions of Namibia and tested by PCR. Positive samples were sequenced and compared to PCV-3 strains circulating globally. Forty-two out of 77 pigs (54.54 %) and 12 out of 55 warthogs (21.82 %) tested positive, demonstrating the presence of PCV-3 in the country and suggesting that the high biosecurity measures implemented in the commercial farms that previously tested negative for PCV-3 probably prevented viral introduction. The partial ORF2 gene was successfully sequenced in samples from 27 pigs and 6 warthogs. Genetically, the identified strains were part of 3 distinct groups which included both backyard pigs and warthogs from different regions of Namibia. There is also evidence for the occurrence of multiple introduction events most likely from Asian countries, either directly into Namibia or through other African countries. Considering the strict Namibian regulations on live animal importation, understanding the source of viral introduction is challenging, although semen importation or the habit of feeding backyard pigs with human food waste might have played a role. Pig exchanges between farms for breeding purposes or wildlife movements could also have been involved in PCV-3 dispersal within Namibia. Despite the significant advances in the field, further studies should be undertaken to properly understand PCV-3 epidemiology in Namibia and its impact on pig productivity and wildlife health.
自 2015 年首次发现以来，猪圆环病毒 3 型（PCV-3）已在全球范围内被频繁报道，并存在多种临床病症，尽管其对猪健康和生产力的影响仍存在争议。然而，非洲地区有关 PCV-3 的存在的数据有限。此前在纳米比亚的商业猪群中进行的一项研究未能发现该病原体。在本研究中，评估了后院农场的病毒循环情况，这些农场的生物安全措施较低，农场之间经常交换动物。还评估了疣猪对 PCV-3 感染的易感性及其潜在的流行病学作用。在纳米比亚不同地区收集了来自后院养猪场的 77 头猪和 55 头疣猪的扁桃体，并通过 PCR 进行检测。对阳性样本进行测序，并与全球流行的 PCV-3 株进行比较。77 头猪中有 42 头（54.54%）和 55 头疣猪中有 12 头（21.82%）检测呈阳性，表明该国存在 PCV-3，并表明以前对 PCV-3 检测呈阴性的商业农场实施的高生物安全措施可能阻止了病毒的传入。成功对来自 27 头猪和 6 头疣猪的样本进行了部分 ORF2 基因测序。遗传上，鉴定出的毒株属于 3 个不同的组，其中包括来自纳米比亚不同地区的后院猪和疣猪。也有证据表明发生了多次传入事件，这些事件很可能来自亚洲国家，要么直接传入纳米比亚，要么通过其他非洲国家传入。考虑到纳米比亚对活体动物进口的严格规定，了解病毒传入的来源具有挑战性，尽管精液进口或后院猪食用人类食物垃圾的习惯可能发挥了作用。出于繁殖目的或野生动物活动而在农场之间交换猪也可能导致 PCV-3 在纳米比亚的传播。尽管在该领域取得了重大进展，但仍应进行进一步的研究，以正确了解纳米比亚的 PCV-3 流行病学及其对猪生产力和野生动物健康的影响。
