ONIRIS, UMR 1300 Bio-Agression, Epidémiologie et Analyse de Risque, Nantes F-44307, France.
Prev Vet Med. 2011 Aug 1;101(1-2):51-7. doi: 10.1016/j.prevetmed.2011.05.005. Epub 2011 Jun 8.
Coxiella burnetii is the causal agent of Q fever, a worldwide spread zoonosis. Prevention of C. burnetii shedding in cattle is critical to control the spread of the pathogen between animals, and from animals to humans. Vaccination with a phase 1 vaccine has been shown to be effective in preventing shedding when implemented in still susceptible animals, even in infected cattle herds. The identification of these animals (dairy cows and nulliparous females) as targets for vaccination consequently is crucial. Hygiene measures conventionally also are implemented, but their relative impact on C. burnetii diffusion remains unknown. The objectives of this study therefore were to (i) describe the distribution of the within-herd apparent seroprevalence among cows and nulliparous females and (ii) to explore the association between management practices and herd characteristics on the one hand, and these seroprevalences on the other. In a sample of 100 naturally and clinically infected dairy herds, blood samples were taken systematically from all nulliparous females (older than 12 months) and cows, and serologically tested. Information on herd characteristics and management practices were collected through a questionnaire filled in by each farmer. The variation in within-herd seroprevalence among cows and the risk for a herd of having at least one seropositive nulliparous female were investigated using multivariate (linear and logistic respectively) regression models. Median within-herd seroprevalence was 0.32 (Q1=0.22; Q3=0.43). We observed a low to null (median=0.01; Q1=0; Q3=0.10) within-herd seroprevalence in nulliparous females contrary to a high value (median=0.42) and variability (Q1=0.28; Q3=0.56) in cows. Only a few herd characteristics and management practices were found to be related to seroprevalence. Within-herd seroprevalence in cows was found to be significantly (P<0.10) higher in herds (i) with a number of cows<46, (ii) with seasonal calving, and (iii) with grazing or contact through the fence with other ruminant herds. The risk of having at least one seropositive nulliparous female was increased in herds (i) with seasonal calving and (ii) where the foetus and/or the placenta of aborted cows were not systematically removed. Our findings support, in addition to the implementation of high level of hygiene measures, the relevance of vaccination (at least in nulliparous females) as a method to control the spread of C. burnetii within an infected herd, as vaccination is effective in susceptible animals and given that nulliparous females are mostly not infected even in infected herds.
贝氏考克斯氏体是 Q 热的病原体，是一种分布广泛的动物传染病。预防牛群中贝氏考克斯氏体的脱落对于控制病原体在动物之间以及从动物传播到人类的传播至关重要。在易感动物中接种 1 期疫苗已被证明可有效预防脱落，即使在感染牛群中也是如此。因此，确定这些动物（奶牛和初产未孕母牛）为疫苗接种目标至关重要。常规实施卫生措施，但它们对贝氏考克斯氏体扩散的相对影响仍不清楚。本研究的目的是：（i）描述牛群和初产未孕母牛的群内血清阳性率分布；（ii）探讨管理实践和畜群特征与这些血清阳性率之间的关系。在 100 个自然和临床感染的奶牛群的样本中，系统地从所有初产未孕母牛（12 个月以上）和奶牛中采集血液样本，并进行血清学检测。通过每个农民填写的问卷收集了畜群特征和管理实践信息。使用多变量（线性和逻辑分别）回归模型研究了牛群内的血清阳性率变化和畜群至少有一个血清阳性初产未孕母牛的风险。牛群内的血清阳性率中位数为 0.32（Q1=0.22；Q3=0.43）。我们观察到，与奶牛相比，初产未孕母牛的血清阳性率较低至为零（中位数=0.01；Q1=0；Q3=0.10），而奶牛的血清阳性率则较高（中位数=0.42）且差异较大（Q1=0.28；Q3=0.56）。仅发现少数畜群特征和管理实践与血清阳性率有关。发现牛群内的血清阳性率在以下情况下（i）奶牛数量<46，（ii）季节性产犊，以及（iii）放牧或通过围栏与其他反刍动物群接触时显著（P<0.10）升高。在（i）季节性产犊和（ii）系统清除流产牛的胎儿和/或胎盘的畜群中，初产未孕母牛血清阳性的风险增加。我们的研究结果支持在实施高水平卫生措施的基础上，将疫苗接种（至少在初产未孕母牛中）作为控制感染畜群中贝氏考克斯氏体传播的一种方法，因为疫苗接种对易感动物有效，而且即使在感染畜群中，初产未孕母牛也大多未感染。
