Data from: Borrelia burgdorferi sensu lato spirochetes in wild birds in northwestern California: associations with ecological factors, bird behavior and tick infestation

Although Borrelia burgdorferi sensu lato (s.l.) are found in a great diversity of vertebrates, most studies in North America have focused on the role of mammals as spirochete reservoir hosts. We investigated the roles of birds as hosts for subadult Ixodes pacificus ticks and potential reservoirs of the Lyme disease spirochete B. burgdorferi sensu stricto (s.s.) in northwestern California. Overall, 623 birds representing 53 species yielded 284 I. pacificus larvae and nymphs. We used generalized linear models and zero-inflated negative binomial models to determine associations of bird behaviors, taxonomic relationships and infestation by I. pacificus with borrelial infection in the birds. Infection status in birds was best explained by taxonomic order, number of infesting nymphs, sampling year, and log-transformed average body weight. Presence and counts of larvae and nymphs could be predicted by ground- or bark-foraging behavior and contact with dense oak woodland. Molecular analysis yielded the first reported detection of Borrelia bissettii in birds. Moreover, our data suggest that the Golden-crowned Sparrow (Zonotrichia atricapilla), a non-resident species, could be an important reservoir for B. burgdorferi s.s. Of 12 individual birds (9 species) that carried B. burgdorferi s.l.-infected larvae, no birds carried the same genospecies of B. burgdorferi s.l. in their blood as were present in the infected larvae removed from them. Possible reasons for this discrepancy are discussed. Our study is the first to explicitly incorporate both taxonomic relationships and behaviors as predictor variables to identify putative avian reservoirs of B. burgdorferi s.l. Our findings underscore the importance of bird behavior to explain local tick infestation and Borrelia infection in these animals, and suggest the potential for bird-mediated geographic spread of vector ticks and spirochetes in the far-western United States.

尽管伯氏疏螺旋体广义群（Borrelia burgdorferi sensu lato, s.l.）可在多样的脊椎动物体内被检出，但北美地区的多数研究均聚焦于哺乳类作为该螺旋体储存宿主的作用。本研究针对加利福尼亚州西北部，探究了鸟类作为亚成体太平洋硬蜱（Ixodes pacificus）宿主，以及莱姆病致病菌伯氏疏螺旋体狭义群（Borrelia burgdorferi sensu stricto, s.s.）潜在储存宿主的角色。本次研究共计采集到隶属于53个物种的623只鸟类，从中获得284只太平洋硬蜱幼虫与若虫。我们采用广义线性模型与零膨胀负二项模型，分析鸟类行为、分类学亲缘关系以及太平洋硬蜱侵染与鸟类伯氏疏螺旋体感染之间的关联。鸟类的伯氏疏螺旋体感染状态，最优预测因子为分类目阶元、侵染若虫数量、采样年份以及经对数转换后的平均体重。幼虫与若虫的侵染发生率及侵染数量，可通过鸟类的地面/树皮取食行为，以及与致密栎林的接触情况进行预测。分子生物学检测首次在鸟类体内检出比斯提疏螺旋体（Borrelia bissettii）。此外，本研究数据提示，非居留性物种金顶带鹀（Zonotrichia atricapilla）可能是伯氏疏螺旋体狭义群的重要储存宿主。在12只（隶属于9个物种）携带被伯氏疏螺旋体广义群侵染的蜱幼虫的个体鸟类中，无一只其血液内的伯氏疏螺旋体基因种与从其体内移除的感染蜱幼虫所携带的基因种一致。本文对该现象可能的成因进行了讨论。本研究首次同时将分类学亲缘关系与行为特征作为预测变量，以明确伯氏疏螺旋体广义群的候选鸟类储存宿主。本研究结果凸显了鸟类行为在解释当地蜱虫侵染与鸟类伯氏疏螺旋体感染中的重要性，并提示在美国远西部区域，鸟类可能介导媒介蜱虫与螺旋体的地理扩散。