Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany.
Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany.
Transbound Emerg Dis. 2019 Jan;66(1):454-462. doi: 10.1111/tbed.13045. Epub 2018 Nov 16.
Since its first appearance in 2011, Schmallenberg virus (SBV) has been repeatedly detected in aborted ruminant foetuses or severely malformed newborns whose mothers were naturally infected during pregnancy. However, especially the knowledge about dynamics of foetal infection in cattle is still scarce. Therefore, a total of 36 pregnant heifers were experimentally infected during two animal trials with SBV between days 60 and 150 of gestation. The foetuses were collected between 10 and 35 days after infection and virologically and pathologically investigated. Overall, 33 heifers yielded normally developed, macroscopically inconspicuous foetuses, but abundant virus replication was evident at the maternal/foetal interface and viral genome was detectable in at least one organ system of 18 out of 35 foetuses. One heifer was found to be not pregnant at autopsy. One of the animals aborted at day 4 after infection, viral RNA was detectable in the lymphatic tissue of the dam, in the maternal and foetal placenta, and in organs and lymphatic tissue of the foetus. In another foetus, SBV typical malformations like torticollis and arthrogryposis were observed. The corresponding dam was infected at day 90 of pregnancy and viral genome was detectable in the cerebellum of the unborn. Interestingly, no common patterns of infected foetal organs or maternal/foetal placentas could be identified, and both, sites of virus replication and genome loads, varied to a high degree in the individual foetuses. It is therefore concluded, that SBV infects in many cases also the bovine foetus of naïve pregnant cattle, however, the experimentally observed low abortion/malformation rate is in concordance to the reported low rates in the field during the first outbreak wave following the introduction of SBV. This observation speaks for a natural resistance of most bovine foetuses even during the vulnerable phase of early pregnancy, which has to be further studied in the future.
自 2011 年首次出现以来，沙氏贝科病毒（SBV）已在流产的反刍动物胎儿或严重畸形的新生牛中反复检测到，这些新生牛的母亲在怀孕期间自然感染了 SBV。然而，特别是关于牛胎儿感染的动态知识仍然缺乏。因此，在两次动物试验中，共有 36 头怀孕的小母牛在妊娠第 60 至 150 天期间用 SBV 进行了实验性感染。在感染后 10 至 35 天收集胎儿，并进行病毒学和病理学检查。总体而言，33 头小母牛产下了正常发育、大体上无明显异常的胎儿，但在至少 18 头胎儿的一个或多个器官系统中可检测到大量病毒复制。一头小母牛在尸检时被发现未怀孕。一头动物在感染后第 4 天流产，在母体的淋巴组织、母体和胎儿胎盘以及胎儿的器官和淋巴组织中可检测到病毒 RNA。在另一头胎儿中，观察到 SBV 典型的畸形，如斜颈和关节挛缩。相应的母畜在妊娠第 90 天感染，未出生胎儿的小脑可检测到病毒基因组。有趣的是，无法确定受感染胎儿器官或母体/胎儿胎盘的共同模式，并且在个体胎儿中，病毒复制的部位和基因组载量差异很大。因此可以得出结论，在许多情况下，SBV 也会感染初次怀孕的无经验牛的胎儿，但实验观察到的低流产/畸形率与 SBV 引入后的首次暴发波中报告的低流行率一致。这一观察结果表明，大多数牛胎儿即使在怀孕早期的脆弱阶段也具有天然的抵抗力，这需要在未来进一步研究。
