Lynsdale Carly L, Mumby Hannah S, Hayward Adam D, Mar Khyne U, Lummaa Virpi
Department of Animal and Plant Sciences University of Sheffield Sheffield UK.
Department of Zoology University of Cambridge Cambridge UK.
Ecol Evol. 2017 Nov 12;7(24):10904-10915. doi: 10.1002/ece3.3559. eCollection 2017 Dec.
Parasites can cause severe host morbidity and threaten survival. As parasites are generally aggregated within certain host demographics, they are likely to affect a small proportion of the entire population, with specific hosts being at particular risk. However, little is known as to whether increased host mortality from parasitic causes is experienced by specific host demographics. Outside of theoretical studies, there is a paucity of literature concerning dynamics of parasite-associated host mortality. Empirical evidence mainly focuses on short-lived hosts or model systems, with data lacking from long-lived wild or semi-wild vertebrate populations. We investigated parasite-associated mortality utilizing a multigenerational database of mortality, health, and reproductive data for over 4,000 semi-captive timber elephants (), with known causes of death for mortality events. We determined variation in mortality according to a number of host traits that are commonly associated with variation in parasitism within mammals: age, sex, and reproductive investment in females. We found that potentially parasite-associated mortality varied significantly across elephant ages, with individuals at extremes of lifespan (young and old) at highest risk. Mortality probability was significantly higher for males across all ages. Female reproducers experienced a lower probability of potentially parasite-associated mortality than females who did not reproduce at any investigated time frame. Our results demonstrate increased potentially parasite-associated mortality within particular demographic groups. These groups (males, juveniles, elderly adults) have been identified in other studies as susceptible to parasitism, stressing the need for further work investigating links between infection and mortality. Furthermore, we show variation between reproductive and non-reproductive females, with mothers being less at risk of potentially parasite mortality than nonreproducers.
寄生虫可导致宿主严重发病并威胁其生存。由于寄生虫通常在特定宿主群体中聚集，它们可能仅影响整个人口中的一小部分，特定宿主面临着特殊风险。然而，对于特定宿主群体是否因寄生虫感染导致宿主死亡率增加，我们知之甚少。除了理论研究外，关于寄生虫相关宿主死亡率动态的文献也很少。实证证据主要集中在寿命较短的宿主或模型系统，缺乏来自长寿野生或半野生脊椎动物种群的数据。我们利用一个包含4000多头半圈养亚洲象的多代死亡率、健康和繁殖数据的数据库，调查了与寄生虫相关的死亡率，该数据库记录了死亡事件的已知死因。我们根据一些在哺乳动物中通常与寄生虫感染变化相关的宿主特征，即年龄、性别以及雌性的繁殖投入，确定了死亡率的差异。我们发现，潜在的与寄生虫相关的死亡率在大象的不同年龄段有显著差异，寿命两端（幼年和老年）的个体风险最高。所有年龄段的雄性死亡率概率都显著更高。在任何调查时间段内，处于繁殖期的雌性与寄生虫相关的潜在死亡率概率低于未繁殖的雌性。我们的研究结果表明特定人群中与寄生虫相关的潜在死亡率有所增加。在其他研究中，这些人群（雄性、幼年、老年个体）被确定为易受寄生虫感染，这凸显了进一步研究感染与死亡率之间联系的必要性。此外，我们还发现了繁殖期和非繁殖期雌性之间的差异，即母亲比未生育的雌性面临潜在寄生虫死亡的风险更低。
