Data from: Links between blood parasites, blood chemistry, and the survival probability of nestling American crows

1. Many studies have used the avian haemosporidians (Leucocytozoon, Plasmodium, and Haemoproteus) to test hypotheses of host-parasite co-evolution, yet documented health and survival consequences of these blood parasites vary among studies and generalizations about their pathogenicity are debatable. In general, the negative effects of the haemosporidians are likely to be greatest during acute infections of young birds, yet most previous studies in wild passerines have examined chronic effects in adults. 2. Here, we evaluated responses of nestling American crows (Corvus brachyrhynchos) to acute infection (prevalence and burden), as well as its short- and long-term survival consequences. 3. We used panel of nine hematological and biochemical parameters that are regularly used to evaluate the health of domestic animals, including leukocyte profiles, hematocrit, and plasma proteins. We assessed the effects of infection on survival in a mark-recapture framework. 4. Overall, 56% of crows (n = 321 samples) were infected by at least one of the three genera. Infections by all genera were associated with elevated plasma proteins and globulins, which could indicate an adaptive immune response. However, only Plasmodium infections were associated with low hematocrit (anemia) and lower fledging success, possibly mediated by the negative effect of low hematocrit values on body condition. Moreover, early Plasmodium infection (< 40 days of age) had long-term survival implications: it was associated with lower apparent survival probability within three years after fledging. 5. These results suggest that young crows mounted an adaptive immune response to all three genera. Short- and long-term pathological effects, however, were only apparent with Plasmodium infections.

1. 诸多研究已利用禽血孢子虫（avian haemosporidians）——涵盖住白细胞虫属（Leucocytozoon）、疟原虫属（Plasmodium）与血变原虫属（Haemoproteus）——检验宿主-寄生虫协同进化相关假说，但不同研究中记录的此类血液寄生虫对宿主健康与存活的影响存在差异，且关于其致病性的学界共识尚存争议。总体而言，禽血孢子虫的负面影响在幼鸟急性感染阶段通常最为显著，但此前多数针对野生雀形目鸟类的研究仅聚焦于成体的慢性感染效应。2. 本研究以雏鸟美洲鸦（Corvus brachyrhynchos）为研究对象，评估其对急性感染的响应（包括感染率与感染负荷），以及该感染带来的短期与长期存活后果。3. 本研究采用一套包含9项指标的血液学与生化检测面板，该面板常用于家养动物的健康评估，涵盖白细胞分类计数、血细胞比容与血浆蛋白等指标；同时通过标记重捕法分析感染对宿主存活的影响。4. 整体而言，共计321份样本中，56%的美洲鸦至少感染了上述3个属中的1种。上述三个属的寄生虫感染均与血浆蛋白及球蛋白水平升高相关，这一现象或提示机体存在适应性免疫应答。但仅疟原虫属感染与血细胞比容降低（贫血）及出巢成功率下降存在关联，该关联可能由低血细胞比容对个体身体状况的负面影响所介导。此外，40日龄前的早期疟原虫感染会产生长期存活影响：该感染与雏鸟出巢后3年内的表观存活概率降低显著相关。5. 上述结果表明，幼龄美洲鸦对上述三类寄生虫均启动了适应性免疫应答；但仅疟原虫属感染会显现出短期与长期的病理效应。