Department of Veterinary and Biomedical Sciences, Animal Disease Research and Diagnostic Laboratory, South Dakota State University, Brookings, South Dakota, USA.
Department of Veterinary and Biomedical Sciences, Animal Disease Research and Diagnostic Laboratory, South Dakota State University, Brookings, South Dakota, USA
J Virol. 2019 Oct 15;93(21). doi: 10.1128/JVI.00819-19. Print 2019 Nov 1.
Senecavirus A (SVA) is a picornavirus that causes acute vesicular disease (VD), that is clinically indistinguishable from foot-and-mouth disease (FMD), in pigs. Notably, SVA RNA has been detected in lymphoid tissues of infected animals several weeks following resolution of the clinical disease, suggesting that the virus may persist in select host tissues. Here, we investigated the occurrence of persistent SVA infection and the contribution of stressors (transportation, immunosuppression, or parturition) to acute disease and recrudescence from persistent SVA infection. Our results show that transportation stress leads to a slight increase in disease severity following infection. During persistence, transportation, immunosuppression, and parturition stressors did not lead to overt/recrudescent clinical disease, but intermittent viremia and virus shedding were detected up to day 60 postinfection (p.i.) in all treatment groups following stress stimulation. Notably, real-time PCR and hybridization (ISH) assays confirmed that the tonsil harbors SVA RNA during the persistent phase of infection. Immunofluorescence assays (IFA) specific for double-stranded RNA (dsRNA) demonstrated the presence of double-stranded viral RNA in tonsillar cells. Most importantly, infectious SVA was isolated from the tonsil of two animals on day 60 p.i., confirming the occurrence of carrier animals following SVA infection. These findings were supported by the fact that contact piglets (11/44) born to persistently infected sows were infected by SVA, demonstrating successful transmission of the virus from carrier sows to contact piglets. Results here confirm the establishment of persistent infection by SVA and demonstrate successful transmission of the virus from persistently infected animals. Persistent viral infections have significant implications for disease control strategies. Previous studies demonstrated the persistence of SVA RNA in the tonsil of experimentally or naturally infected animals long after resolution of the clinical disease. Here, we showed that SVA establishes persistent infection in SVA-infected animals, with the tonsil serving as one of the sites of virus persistence. Importantly, persistently infected carrier animals shedding SVA in oral and nasal secretions or feces can serve as sources of infection to other susceptible animals, as evidenced by successful transmission of SVA from persistently infected sows to contact piglets. These findings unveil an important aspect of SVA infection biology, suggesting that persistently infected pigs may function as reservoirs for SVA.
塞尼卡病毒 A（SVA）是一种小 RNA 病毒，可引起猪的急性水疱病（VD），其临床症状与口蹄疫（FMD）无法区分。值得注意的是，在临床疾病缓解后数周，已在感染动物的淋巴组织中检测到 SVA RNA，这表明该病毒可能在特定宿主组织中持续存在。在这里，我们研究了持续性 SVA 感染的发生以及应激源（运输、免疫抑制或分娩）对急性疾病和持续性 SVA 感染复发的影响。我们的结果表明，运输应激会导致感染后疾病严重程度略有增加。在持续性感染期间，运输、免疫抑制和分娩应激源并未导致明显/复发的临床疾病，但在应激刺激后，所有治疗组在感染后第 60 天（p.i.）仍可检测到间歇性病毒血症和病毒脱落。值得注意的是，实时 PCR 和杂交（ISH）检测证实，在感染的持续性阶段，扁桃体含有 SVA RNA。针对双链 RNA（dsRNA）的免疫荧光检测（IFA）显示，扁桃体细胞中存在双链病毒 RNA。最重要的是，在感染后第 60 天，从 2 只动物的扁桃体分离到了传染性 SVA，证实了 SVA 感染后存在带毒动物。接触感染母猪所生的仔猪（44 头中的 11 头）感染了 SVA，这一事实支持了这一发现，表明病毒从带毒母猪成功传播给了接触仔猪。这些发现得到了以下事实的支持：在临床疾病缓解后很长一段时间内，实验或自然感染的动物的扁桃体中都可检测到 SVA RNA 的持续性存在。在这里，我们表明 SVA 在 SVA 感染动物中建立了持续性感染，扁桃体是病毒持续存在的部位之一。重要的是，在口腔和鼻腔分泌物或粪便中排出 SVA 的持续性感染带毒动物可成为其他易感动物的感染源，这从感染母猪成功传播 SVA 给接触仔猪中得到了证明。这些发现揭示了 SVA 感染生物学的一个重要方面，表明持续性感染的猪可能是 SVA 的储存宿主。
