Analyses of livestock movement networks has become key to understanding an industry's vulnerability to infectious disease spread and for identifying farms that play disproportionate roles in pathogen dissemination. In addition to animal movements, many pathogens can spread between farms via mechanisms mediated by spatial proximity. Heterogeneities in contact patterns based on spatial proximity are less commonly considered in network studies, and studies that jointly consider spatial connectivity and animal movement are rare. The objective of this study was to determine the extent to which movement versus spatial proximity networks determine the distribution of an economically important endemic virus, porcine reproductive and respiratory syndrome virus (PRRSV), within a swine-dense region of the U.S. PRRSV can be classified into numerous phylogenetic lineages. Such data can be used to better resolve between-farm infection chains and elucidate types of contact most associated with transmission. Here, we construct movement and spatial proximity networks; farms within the networks were classified as cases if a given PRRSV lineage had been recovered at least once in a year for each of three years analyzed. We evaluated six lineages and sub-lineages across three years, and evaluated the epidemiological relevance of each network by applying network k-tests to statistically evaluate whether the pattern of case occurrence within the network was consistent with transmission via network linkages. Our results indicated that animal movements, not local area spread, play a dominant role in shaping transmission pathways, though there were differences amongst lineages. The median number of case farms inter-linked via animal movements was approximately 4.1x higher than random expectations (range: 1.7-13.7; p < 0.05, network k-test), whereas this measure was only 2.7x higher than random expectations for farms linked via spatial proximity (range: 1.3-5.4; p < 0.05, network k-test). For spatial proximity networks, contact based on proximities of <5 km appeared to have greater epidemiological relevance than longer distances, likely related to diminishing probabilities of local area spread at greater distances. However, the greater overall levels of connectivity of the spatial network compared to the movement network highlights the vulnerability of pig populations to widespread transmission via this route. By combining genetic data with network analysis, this research advances our understanding of dynamics of between-farm spread of PRRSV, helps establish the relative importance of transmission via animal movements versus local area spread, and highlights the potential for targeted control strategies based upon heterogeneities in network connectivity.

中文翻译：

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在形成遗传多样性病毒的传播途径中，动物的运动和空间连通性网络形成对比。

对牲畜活动网络的分析已成为了解该行业对传染病传播的脆弱性以及确定在病原体传播中起不成比例作用的农场的关键。除动物运动外，许多病原体还可以通过空间邻近性介导的机制在农场之间传播。在网络研究中，较少考虑基于空间邻近性的接触模式的异质性，而很少考虑将空间连通性和动物运动结合起来的研究。这项研究的目的是确定运动与空间邻近网络在多大程度上确定了在美国猪密集地区内经济上重要的地方性病毒，猪繁殖与呼吸综合征病毒（PRRSV）的分布。PRRSV可以分为许多种系。此类数据可用于更好地解析农场之间的感染链，并阐明与传播最相关的接触类型。在这里，我们构建运动和空间邻近网络；网络中的农场被分类为以下情况：如果给定的PRRSV谱系在所分析的三年中的每一年中每年至少恢复一次。我们评估了三年中的六个血统和子血统，并通过应用网络k检验来统计评估网络内病例的发生方式是否与通过网络链接传播相一致，从而评估了每个网络的流行病学相关性。我们的结果表明，动物运动而不是局部传播在塑造传播途径中起着主导作用，尽管血统之间存在差异。通过动物运动相互联系的案例农场的中位数比随机预期高约4.1倍（范围：1.7-13.7； p <0.05，网络k检验），而该指标仅比农场随机预期高2.7倍通过空间接近度链接（范围：1.3-5.4； p <0.05，网络k检验）。对于空间邻近网络，基于接近度小于5 km的接触似乎比更长距离具有更大的流行病学相关性，可能与减小在更大距离上传播的本地区域的概率有关。但是，与移动网络相比，空间网络的总体连通性更高，这突出表明了猪种群对通过此途径进行广泛传播的脆弱性。通过结合遗传数据和网络分析，