Data from: Predictors and immunological correlates of sublethal mercury exposure in vampire bats

Mercury (Hg) is a pervasive heavy metal that often enters the environment from anthropogenic sources such as gold mining and agriculture. Chronic exposure to Hg can impair immune function, reducing the ability of animals to resist or recover from infections. How Hg influences immunity and susceptibility remains unknown for bats, which appear immunologically distinct from other mammals and are reservoir hosts of many pathogens of importance to human and animal health. We here quantify total Hg (THg) in hair collected from common vampire bats (Desmodus rotundus), which feed on blood and are the main reservoir hosts of rabies virus in Latin America. We examine how diet, sampling site and year, and bat demography influence THg and test the consequences of this variation for eight measures of immune function. In two populations from Belize, THg concentrations in bats were best explained by an interaction between long-term diet inferred from stable isotopes and year. Bats that foraged more consistently on domestic animals exhibited higher THg. However, relationships between diet and THg were evident only in 2015 but not in 2014, which could reflect recent environmental perturbations associated with agriculture. THg concentrations were low relative to values previously observed in other bat species but still correlated with bat immunity. Bats with higher THg had more neutrophils, weaker bacterial killing ability, and impaired innate immunity. These patterns suggest that temporal variation in Hg exposure may impair bat innate immunity and increase susceptibility to pathogens such as bacteria. Unexpected associations between low-level Hg exposure and immune function underscore the need to better understand the environmental sources of Hg exposure in bats and the consequences for bat immunity and susceptibility.汞（Mercury, Hg）是一种广泛分布的重金属，常通过金矿开采、农业等人为来源进入环境。长期暴露于汞会损害免疫功能，降低动物抵抗感染或从感染中恢复的能力。目前关于汞如何影响蝙蝠的免疫功能与感染易感性的研究仍属空白：蝙蝠在免疫学层面与其他哺乳动物存在显著差异，同时是诸多对人类与动物健康具有重要意义的病原体的储存宿主。本研究通过采集普通吸血蝠（Desmodus rotundus，以血液为食，是拉丁美洲狂犬病病毒（rabies virus）的主要储存宿主）的毛发，对其中的总汞（Total Hg, THg）含量进行定量分析。我们探讨了饮食、采样地点与年份、蝙蝠种群统计特征对总汞含量的影响，并检验了该含量差异对八项免疫功能指标的作用效果。在伯利兹的两个蝙蝠种群中，蝙蝠体内的总汞浓度最适宜的解释模型为基于稳定同位素（stable isotopes）推断的长期饮食与采样年份的交互效应。更持续取食家畜的蝙蝠体内总汞含量更高，但饮食与总汞含量的相关性仅在2015年显现，2014年未观察到此关联，这或反映了近年与农业相关的环境扰动。相较于此前其他蝙蝠物种的检测值，本研究中蝙蝠的总汞浓度处于较低水平，但仍与蝙蝠免疫功能存在关联。总汞含量更高的蝙蝠，其中性粒细胞（neutrophils）数量更多、细菌杀伤能力更弱，且先天免疫（innate immunity）功能受损。上述结果表明，汞暴露的时间变异或会损害蝙蝠的先天免疫功能，并提升其对细菌等病原体的感染易感性。低水平汞暴露与免疫功能间的意外关联，凸显了我们需要进一步明确蝙蝠体内汞暴露的环境来源，以及其对蝙蝠免疫功能与感染易感性的影响。