Parasite rearing and infection temperatures jointly influence disease transmission and shape seasonality of epidemics
Parasite rearing and infection temperatures jointly influence disease transmission and shape seasonality of epidemics
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寄生虫饲养和感染温度共同影响疾病传播并影响流行病的季节性
DOI：
10.1002/ecy.2430
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发表时间：
2018
期刊：
影响因子：
4.8
通讯作者：
Hall, Spencer R.
中科院分区：
文献类型：
--
作者：
Shocket, Marta S.;Vergara, Daniela;Sickbert, Andrew J.;Walsman, Jason M.;Strauss, Alexander T.;Hite, Jessica L.;Duffy, Meghan A.;Cáceres, Carla E.;Hall, Spencer R.
季节性流行病通常在自然界爆发，并由许多机制驱动。在这里，我们提出了一种新的机制，可以确定季节性流行病的规模和时间：饲养环境改变寄生虫的性能。当寄生虫产生的环境条件影响其表现时，这种机制就会出现-与当前环境无关。为了说明“饲养效应”的潜力，我们展示了温度如何通过寄生虫饲养温度和感染温度影响水蚤真菌疾病系统中的感染风险（传播率）。在秋季流行期间，浮游动物宿主接触（吃）在逐渐冷却的环境中饲养的真菌寄生虫（孢子）。为了描述饲养温度对暴露和感染温度的影响，我们使用实验室实验来参数化传播率的机械模型。我们还评估了饲养效果，从流行病在冷却湖收集孢子。我们发现真菌孢子在温暖的温度下饲养时更具感染性（在实验室和三个湖泊中的两个）。此外，宿主的暴露（觅食）率随着感染温度的升高而增加。因此，这两种机制都导致传播率随着秋季流行季节（从夏季到冬季）气温的下降而下降。模拟显示了这些温度驱动的传播率变化如何随着湖泊冷却而导致流行病的减弱。此外，通过热依赖性传播，环境冷却模式的变化可以改变流行病的规模和形状。因此，热环境通过对宿主的影响（暴露率）和寄生虫的传染性（饲养效应）驱动季节性流行病。目前，寄生虫饲养效果的一般性仍然未知。我们的研究结果表明，它们可能提供了一个重要的，但未得到充分重视的机制，温度的季节性流行病。
Seasonal epidemics erupt commonly in nature and are driven by numerous mechanisms. Here, we suggest a new mechanism that could determine the size and timing of seasonal epidemics: rearing environment changes the performance of parasites. This mechanism arises when the environmental conditions in which a parasite is produced impact its performance—independently from the current environment. To illustrate the potential for “rearing effects”, we show how temperature influences infection risk (transmission rate) in aDaphnia‐fungus disease system through both parasite rearing temperature and infection temperature. During autumnal epidemics, zooplankton hosts contact (eat) fungal parasites (spores) reared in a gradually cooling environment. To delineate the effect of rearing temperature from temperature at exposure and infection, we used lab experiments to parameterize a mechanistic model of transmission rate. We also evaluated the rearing effect using spores collected from epidemics in cooling lakes. We found that fungal spores were more infectious when reared at warmer temperatures (in the lab and in two of three lakes). Additionally, the exposure (foraging) rate of hosts increased with warmer infection temperatures. Thus, both mechanisms cause transmission rate to drop as temperature decreases over the autumnal epidemic season (from summer to winter). Simulations show how these temperature‐driven changes in transmission rate can induce waning of epidemics as lakes cool. Furthermore, via thermally dependent transmission, variation in environmental cooling patterns can alter the size and shape of epidemics. Thus, the thermal environment drives seasonal epidemics through effects on hosts (exposure rate) and the infectivity of parasites (a rearing effect). Presently, the generality of parasite rearing effects remains unknown. Our results suggest that they may provide an important but underappreciated mechanism linking temperature to the seasonality of epidemics.