Disease epidemiology in arthropods is altered by the presence of non-protective symbionts

Inherited microbial symbionts can modulate host susceptibility to natural enemy attack. A wider range of symbionts influence host population demography without altering individual susceptibility, and it has been suggested that these may modify host disease risk through altering the rate of exposure to natural enemies. We present the first test of this thesis, specifically testing whether male-killing symbionts alter the epidemiology of a sexually transmitted infection (STI) carried by its host. STIs are typically expected to show female-biased epidemics, and we first present a simple model which indicates that male-biased STI epidemics may occur where symbionts create female-biased population sex ratios. We then examined the dynamics of a STI in the ladybird beetle Adalia bipunctata, which is also host to a male-killing bacterium. We present evidence that male-biased epidemics of the STI are observed in natural populations when the male-killer is common. Laboratory experiments did not s...

遗传型微生物共生体（inherited microbial symbionts）可调节宿主对天敌侵袭的易感性。另有一类分布更广的共生体，可在不改变宿主个体易感性的前提下影响其种群统计学特征，已有研究提出，这类共生体可通过改变宿主接触天敌的概率，进而调整宿主的疾病感染风险。本研究首次对这一假说开展验证，具体探究杀雄型共生体（male-killing symbionts）是否会改变宿主所携带的性传播感染（Sexually Transmitted Infection，STI）的流行病学特征。
通常认为，性传播感染会呈现雌性偏向的流行态势，我们首先构建了一个简单的理论模型，结果表明，当共生体导致种群性比偏向雌性时，或会出现性传播感染的雄性偏向流行现象。随后我们针对异色瓢虫（Adalia bipunctata）体内的性传播感染动态展开研究，该宿主同时还携带有一种杀雄细菌。研究证据显示，当杀雄菌在自然种群中占比较高时，可观测到性传播感染呈现雄性偏向的流行特征。实验室实验并未……