Seasonal dynamics and repeatability of gastrointestinal parasite burdens in wild Soay sheep
Seasonal dynamics and repeatability of gastrointestinal parasite burdens in wild Soay sheep
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野生索伊羊胃肠道寄生虫负荷的季节动态和重复性
DOI：
10.1101/2021.03.10.434794
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Sweeny A
中科院分区：
文献类型：
--
作者：
Sweeny A
季节性是野生动物疾病生态学的普遍特征，但由环境、寄生虫学和宿主因素的复杂相互作用决定。胃肠道寄生虫在野生脊椎动物种群中通常表现出强烈的季节性动态，例如，由于环境对自由生活或媒介生活阶段的影响，以及宿主在其年度周期中的生理和免疫状态的变化。同时，野生种群通常感染多种寄生虫。共感染寄生虫的季节动态可能因年龄和生殖状态而异，寄生虫之间的关联可能由短期个体内变化或宿主之间一致的长期相互作用驱动。在这里，我们使用粪便样本和鸡蛋计数重复收集单独标记和监测野生Soay羊，是一项长期研究的一部分，调查季节性动态的6个胃肠道寄生虫群（圆线虫，球虫原虫，毛细线虫，类圆线虫，线虫，和莫尼茨）。患病率和丰度一般倾向于较高的春季和夏季，和负担较高的羔羊比成人。在高度流行的圆线虫组，我们发现的差异，在季节性的卵计数取决于成年人的生殖状态。繁殖母羊增加了计数在春天出生的时候，然后在夏季下降丰富，而贫瘠的母羊几乎没有证据表明季节性。男性在春季和夏季的鸡蛋数量持续上升，性别差异仅在夏季非常明显。与此相反，在同样流行的球虫，我们发现了一个高峰，粪便卵囊计数在春季，但男性，不育和怀孕母羊之间的季节性没有差异。使用多变量混合效应模型，我们继续表明，无论是圆线虫和球虫计数是适度重复跨季节的个人。我们进一步表明，圆线虫和球虫计数之间明显的正相关性是由两种寄生虫负荷的短期个体内变化驱动的，而不是长期个体间的协变。总的来说，我们的研究结果表明，季节性在人口和寄生虫群体中各不相同，并强调了调查随着时间的推移波动的易感性和暴露的价值，以了解人口的流行病学。
Seasonality is a ubiquitous feature of wildlife disease ecology, but is determined by a complex interplay of environmental, parasitological and host factors. Gastrointestinal parasites often exhibit strong seasonal dynamics in wild vertebrate populations due to, for example, environmental influences on free-living or vectored life stages, and variation in the physiological and immune status of hosts across their annual cycle. At the same time, wild populations are typically infected with multiple parasites. The seasonal dynamics of co-infecting parasites may differ depending on age and reproductive status, and associations among parasites may be driven by short-term within-individual changes or longer-term interactions that are consistent among hosts. Here, we used faecal samples and egg counts collected repeatedly from individually marked and monitored wild Soay sheep that were part of a long-term study to investigate seasonal dynamics of six gastrointestinal parasite groups (strongyle nematodes, coccidian protozoa,Capillaria, Strongyloides, Nematodirus, andMoniezia). Prevalence and abundance generally tended to be higher spring and summer, and burdens were higher in lambs than adults. Within the highly prevalent strongyle nematode group, we found differences in seasonality of egg counts depending on adult reproductive status. Reproductive ewes had increased counts in spring around the time of birth followed by a drop in abundance in summer, while barren ewes showed little evidence of seasonality. Males showed a sustained rise in egg counts through spring and summer, and sex differences were only strongly apparent in summer. In contrast, in similarly prevalent coccidia we found a peak in faecal oocyst counts in spring but no differences in seasonality among males, barren and pregnant ewes. Using multivariate mixed-effects models, we went on to show that both strongyle and coccidia counts are moderately repeatable across seasons among individuals. We further show that apparent positive correlation between strongyle and coccidia counts was driven by short-term within-individual changes in both parasite burdens rather than long-term among-individual covariation. Overall, our results demonstrate that seasonality varies across demographic and parasite groups and highlight the value of investigating fluctuating susceptibility and exposure over time for understanding epidemiology of a population.
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