Co-infection with microparasites (e.g., bacteria) and macroparasites (e.g., helminths) is often the natural state for wild animals. Despite evidence that gut helminths can bias immune responses away from inflammatory processes, few field studies have examined the role that helminths, or their potential interactions with internal microbial communities, play in modulating immunity in free-living, wild birds. Here, we used anthelmintic drugs to treat wild Song Sparrows (Melospiza melodia) for helminth infections and measured markers of systemic inflammation (heterothermia and locomotor activity) in response to an immune challenge with lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria. Using birds from a population that previously showed high helminth prevalence, we monitored skin temperature and activity remotely using automated radio telemetry. We also collected cloacal swabs to determine whether drug treatment was associated with changes in the cloacal microbiota, and whether cloacal microbial community structure was associated with the severity of birds’ immune responses. Because helminths can reduce the severity of inflammatory immune responses in other species, we predicted that in comparison with untreated control birds, anthelmintic-treated birds would be more lethargic and display higher fevers when challenged with LPS. Consistent with these predictions, anthelmintic-treated birds expressed higher fevers in response to immune challenge. However, all LPS-challenged birds decreased locomotor activity to a similar degree, regardless of anthelmintic treatment. Although several individual indicator bacterial taxa were strongly associated with anthelmintic treatment, this treatment did not alter overall bacterial alpha- and beta- diversity. Similarly, we did not find evidence that bacterial community diversity influenced the severity of immune responses to LPS. These results suggest that under field conditions, natural helminth infection can reduce the severity of songbirds’ thermoregulatory responses (fever) during an immune challenge, without major impacts on internal microbial communities or behavioral responses to infection.

中文翻译：

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驱虫药物调节急性期免疫反应，但不调节野生宋麻雀的微生物群

微生物（如细菌）和大型寄生虫（如蠕虫）的共同感染通常是野生动物的自然状态。尽管有证据表明肠道蠕虫可以使免疫反应远离炎症过程，但很少有实地研究检查蠕虫或它们与内部微生物群落的潜在相互作用在调节自由生活的野生鸟类免疫中所起的作用。在这里，我们使用驱虫药物治疗野生松雀 (Melospiza melodia) 的蠕虫感染，并测量全身炎症的标志物（体温异常和运动活动）以应对脂多糖 (LPS) 的免疫挑战，脂多糖 (LPS) 是革兰氏阴性菌的细胞壁成分细菌。使用先前表现出高蠕虫流行率的人群中的鸟类，我们使用自动无线电遥测远程监测皮肤温度和活动。我们还收集了泄殖腔拭子以确定药物治疗是否与泄殖腔微生物群的变化有关，以及泄殖腔微生物群落结构是否与鸟类免疫反应的严重程度有关。因为蠕虫可以降低其他物种炎症免疫反应的严重程度，我们预测，与未经处理的对照鸟类相比，经驱虫剂处理的鸟类在受到 LPS 攻击时会更加昏昏欲睡并表现出更高的发烧。与这些预测一致，驱虫剂治疗的鸟类在应对免疫挑战时表现出更高的发烧。然而，无论驱虫治疗如何，所有 LPS 攻击的鸟类都以相似的程度降低了运动活动。尽管几个单独的指示细菌类群与驱虫治疗密切相关，但这种治疗并没有改变整体细菌的 α 和 β 多样性。同样，我们没有发现细菌群落多样性影响对 LPS 的免疫反应严重程度的证据。这些结果表明，在野外条件下，天然蠕虫感染可以降低鸣禽在免疫挑战期间的体温调节反应（发烧）的严重程度，而不会对内部微生物群落或对感染的行为反应产生重大影响。