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. 已有诸多研究利用禽血孢子虫（avian haemosporidians，包括住白细胞虫属Leucocytozoon、疟原虫属Plasmodium以及血变原虫属Haemoproteus）检验宿主-寄生虫协同进化假说，但现有研究中关于此类血液寄生虫对宿主健康与存活的影响结果并不一致，其致病性的普遍性结论亦存在争议。总体而言，禽血孢子虫的负面效应在幼鸟急性感染期可能最为显著，但此前针对野生雀形目鸟类的多数研究仅聚焦于成体的慢性感染效应。
2. 本研究针对美洲乌鸦（Corvus brachyrhynchos）的雏鸟，评估其对急性感染（感染率与载虫量）的应答反应，同时探究该感染对雏鸟短期与长期存活的影响。
3. 本研究采用9项常用于评估家养动物健康状况的血液学与生化指标组合，包括白细胞分类、血细胞比容（hematocrit）以及血浆蛋白。我们通过标记重捕（mark-recapture）框架评估感染对存活的影响。
4. 总体而言，321份样本中的56%至少感染了上述3个属中的1种。三类血孢子虫感染均与血浆蛋白及球蛋白水平升高相关，这提示宿主产生了适应性免疫应答。但仅疟原虫属感染与血细胞比容降低（贫血）以及出飞成功率下降相关，其潜在机制可能是低血细胞比容对身体状况产生了负面影响。此外，雏鸟早期（40日龄前）的疟原虫感染会产生长期存活影响：该感染与出飞后3年内的表观存活概率降低相关。
5. 上述结果表明，美洲乌鸦雏鸟对上述3种血孢子虫属均产生了适应性免疫应答。但仅疟原虫属感染才表现出显著的短期与长期病理效应。