The American pika, Ochotona princeps, is projected to decline throughout North America as climate change reduces its range, and pikas have already disappeared from several locations. In addition to climate, disease spillover from lower elevation mammalian species might affect pikas. We sampled pika fleas in Colorado and Montana across elevations ranging from 2896 to 3612 m and screened them for the presence of DNA from rodent-associated bacterial pathogens (Bartonella species and Yersinia pestis) to test the hypothesis that flea exchange between pikas and rodents may lead to occurrence of rodent-associated pathogens in pika ectoparasites. We collected 275 fleas from 74 individual pikas at 5 sites in Colorado and one site in Montana. We found that 5.5% of 275 pika fleas in this study tested positive for rodent-associated Bartonella DNA but that variation in Bartonella infection prevalence in fleas among sites was not driven by elevation. Specifically, we detected DNA sequences from two loci (gltA and rpoB) that are most similar to Bartonella grahamii isolates collected from rodents in Canada. We did not detect Y. pestis DNA in our survey. Our results demonstrate evidence of rodent-associated flea-borne bacteria in pika fleas. These findings are also consistent with the hypothesis that rodent-associated pathogens could be acquired by pikas. Flea-borne pathogen spillover from rodents to pikas has the potential to exacerbate the more direct effects of climate that have been suggested to drive pika declines.

随着气候变化减少其分布范围，预计美洲鼠兔Ochotona Princeps将在整个北美减少，而且鼠兔已经从几个地方消失了。除了气候之外，来自低海拔哺乳动物物种的疾病外溢可能会影响鼠兔。我们在科罗拉多州和蒙大拿州的 2896 米到 3612 米的海拔范围内对鼠兔跳蚤进行了采样，并筛选了它们是否存在来自啮齿动物相关细菌病原体（巴尔通体和鼠疫杆菌）的 DNA。) 以检验鼠兔和啮齿动物之间的跳蚤交换可能导致鼠兔体外寄生虫中与啮齿动物相关的病原体发生的假设。我们从科罗拉多州的 5 个地点和蒙大拿州的一个地点的 74 只鼠兔中收集了 275 只跳蚤。我们发现本研究中 275 只鼠兔跳蚤中有 5.5% 的啮齿动物相关巴尔通体DNA检测呈阳性，但不同地点跳蚤中巴尔通体感染率的差异并不是由海拔高度驱动的。具体来说，我们检测了两个基因座（gltA和rpoB）的DNA 序列，它们与从加拿大啮齿类动物收集的格雷哈姆巴尔通体分离株最相似。我们没有检测到鼠疫耶尔森氏菌我们调查中的 DNA。我们的结果证明鼠兔跳蚤中存在与啮齿动物相关的跳蚤传播细菌的证据。这些发现也与鼠兔可以感染啮齿动物相关病原体的假设一致。从啮齿动物到鼠兔的跳蚤传播病原体有可能加剧气候的更直接影响，而气候影响已被认为是导致鼠兔数量减少的原因。