Schmallenberg virus in Dutch dairy herds: Potential risk factors for high within-herd seroprevalence and malformations in calves, and its impact on productivity
Schmallenberg virus in Dutch dairy herds: Potential risk factors for high within-herd seroprevalence and malformations in calves, and its impact on productivity
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DOI：
10.1016/j.vetmic.2013.11.021
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发表时间：
2014-01-31
影响因子：
3.3
通讯作者：
van Schaik, G.
中科院分区：
文献类型：
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作者：
Veldhuis, A. M. B.;Carp-van Dijken, S.;van Schaik, G.
2011年11月，在荷兰发生发热、产奶量下降和腹泻的奶牛中发现了新的正布尼亚病毒施马伦贝格病毒（SBV） （Muskens et al., 2012）。Tijdschrift voor Diergeneeskunde 137, 112-115)和德国西北部奶牛产奶量下降（Hoffmann et al., 2012）。新发传染病18(3),469-472)，2011年8月/ 9月。本研究旨在量化荷兰乳牛群中SBV高流行率和SBV诱导的新生小牛畸形的危险因素。此外，还估计了SBV感染对牛群死亡率和产奶量的影响。采用病例-对照设计，包括75个临床感染病例群和74个对照群。对照牛群是根据新生牛犊没有畸形和繁殖性能异常来选择的。估计了群体内sbv特异性血清患病率。对群内高SBV血清患病率（bbb50 %）的危险因素和群中新生牛犊畸形的概率进行了量化。此外，还估计了SBV对奶牛产奶量和死亡率的群内影响。动物水平的血清阳性率在病例群中为84.4%(95%置信区间（CI）： 70.8-92.3)，在对照群中为75.8% （95% CI: 67.5-82.5）。完全没有SBV的对照牛群没有出现在研究中。2011年放牧的畜群与室内饲养的畜群相比，高血清患病率（50%）的几率增加（OR 9.9; 95% CI: 2.4-41.2）。此外，当2011年开始放牧时，新生牛犊畸形的几率往往是圈养牛群的2.6倍。在牛群水平上，新生牛犊畸形的发生率与牛群内血清患病率和成年牛疾病的临床表现有关。一旦大坝被感染，SBV垂直传播给胎儿的几率似乎很低。在研究期间，65名农民共提交了146头死产或畸形犊牛，其中19头根据病理调查和/或脑组织RT-qPCR检测被诊断为sbv阳性。根据这些结果以及这些象群的产犊数据，我们粗略估计，2012年2月至9月期间出生的小牛中至少有0.5%感染了SBV。2011年8月底至9月上半月（第35-36周）期间观察到产奶量下降，表明该流行病处于急性阶段。在预计发生SBV感染的4周期间，受影响奶牛群的产奶量总损失约为每头奶牛30-51公斤。鉴于成年奶牛中SBV的表达相对温和，新生牛犊畸形发生率低，因此SBV对死亡率没有或影响有限。(C) 2013 Elsevier B.V.版权所有
In November 2011, the new orthobunyavirus Schmallenberg virus (SBV) was identified in dairy cows that had induced fever, drop in milk production and diarrhoea in the Netherlands (Muskens et al., 2012. Tijdschrift voor Diergeneeskunde 137, 112-115) and a drop in milk production in cows in Northwestern Germany (Hoffmann et al., 2012. Emerging Infectious Diseases 18 (3), 469-472), in August/September 2011. This study aimed at quantifying risk factors for high within-herd prevalence of SBV and SBV-induced malformations in newborn calves in dairy herds in the Netherlands. Additionally, the within-herd impact of SBV infection on mortality rates and milk production was estimated.A case-control design was used, including 75 clinically affected case herds and 74 control herds. Control herds were selected based on absence of malformations in newborn calves and anomalies in reproductive performance. SBV-specific within-herd seroprevalences were estimated. Risk factors for high within-herd SBV seroprevalence (>50%) and the probability of malformed newborn calves in a herd were quantified. In addition, within-herd impact of SBV with regard to milk production and mortality was estimated.Animal-level seroprevalence was 84.4% (95% confidence interval (CI): 70.8-92.3) in case herds and 75.8% (95% CI: 67.5-82.5) in control herds. Control herds that were completely free from SBV were not present in the study. Herds that were grazed in 2011 had an increased odds (OR 9.9; 95% CI: 2.4-41.2)) of a high seroprevalence (>50%) compared to herds that were kept indoors. Also, when grazing was applied in 2011, the odds of malformations in newborn calves tended to be 2.6 times higher compared to herds in which cattle were kept indoors. Incidence of malformations in newborn calves at herd level was associated with both within-herd seroprevalence and clinical expression of the disease in adult cattle.The rate of vertical transmission of SBV to the fetus once a dam gets infected seemed low. A total of 146 stillborn or malformed calves were submitted by 65 farmers during the study period, of which 19 were diagnosed as SBV-positive based on pathological investigation and/or RT-qPCR testing of brain tissue. Based on these results combined with calving data from these herds we roughly estimated that at least 0.5% of the calves born between February and September 2012 have been infected by SBV.A drop in milk production was observed between the end of August 2011 and the first half of September (week 35-36), indicating the acute phase of the epidemic. During a 4-week period in which SBV infection was expected to have occurred, the total loss in milk production in affected dairy herds was around 30-51 kg per cow. SBV had no or limited impact on mortality rates which was as expected given the relatively mild expression of SBV in adult cows and the low incidence of malformations in newborn calves. (C) 2013 Elsevier B.V. All rights reserved.