The virulence-transmission relationship in an obligate killer holds under diverse epidemiological and ecological conditions, but where is the tradeoff?
The virulence-transmission relationship in an obligate killer holds under diverse epidemiological and ecological conditions, but where is the tradeoff?
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DOI：
10.1002/ece3.3532
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发表时间：
2017-12
影响因子：
2.6
通讯作者：
Ben-Ami F
中科院分区：
文献类型：
--
作者：
Ben-Ami F
寄生虫的毒力是进化生物学的主要主题。对毒力进化过程进行建模有望为传染病的管理和疫苗接种战略的实施提供实际的见解。毒力建模的一个关键因素是在寄生虫传播率和宿主寿命之间进行权衡。这一假设对于预测最佳毒力水平至关重要。在这里，我用水蚤大水蚤和它的去势和专性杀死细菌巴氏菌来测试这一假设。在不同的流行病学和生态条件下，毒力-传播关系都是成立的。特别是，寄生虫基因型、绝对和相对剂量以及多次感染的宿主内竞争对观察到的趋势没有显著影响。有趣的是，在这个系统中，毒力和寄生虫传播之间的关系最好用一个包含三次项的模型来解释。在这种关系下，寄生虫传播最初在中等毒力水平达到峰值并达到饱和，但随后随着毒力下降而进一步增加，超过之前的峰值。我的研究结果还强调了使用寄生虫诱导的宿主死亡率作为水平传播寄生虫的“一刀切”的毒力测量方法的问题，而没有考虑寄生虫传播的开始和持续时间以及寄生虫的其他同等毒力效应（例如，宿主阉割）。因此，可能需要数学模型来预测水平传播寄生虫的这些特殊特征是否可以将毒力进化引导到现有模型未设想的方向。
Parasite virulence is a leading theme in evolutionary biology. Modeling the course of virulence evolution holds the promise of providing practical insights into the management of infectious diseases and the implementation of vaccination strategies. A key element of virulence modeling is a tradeoff between parasite transmission rate and host lifespan. This assumption is crucial for predicting the level of optimal virulence. Here, I test this assumption using the water flea Daphnia magna and its castrating and obligate‐killing bacterium Pasteuria ramosa. I found that the virulence–transmission relationship holds under diverse epidemiological and ecological conditions. In particular, parasite genotype, absolute and relative parasite dose, and within‐host competition in multiple infections did not significantly affect the observed trend. Interestingly, the relationship between virulence and parasite transmission in this system is best explained by a model that includes a cubic term. Under this relationship, parasite transmission initially peaks and saturates at an intermediate level of virulence, but then it further increases as virulence decreases, surpassing the previous peak. My findings also highlight the problem of using parasite‐induced host mortality as a “one‐size‐fits‐all” measure of virulence for horizontally transmitted parasites, without considering the onset and duration of parasite transmission as well as other equally virulent effects of parasites (e.g., host castration). Therefore, mathematical models may be required to predict whether these particular characteristics of horizontally transmitted parasites can direct virulence evolution into directions not envisaged by existing models.
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影响因子：
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作者：
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通讯作者：
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发表时间：
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影响因子：
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