Data for: Consequences of microsporidian prior exposure for virus infection outcomes and bumble bee host health

Host-parasite interactions do not occur in a vacuum but in connected multi-parasite networks. Resulting co-exposures and coinfections during an individual host's lifetime can affect host health and infectious disease ecology, including disease outbreaks. However, many host-parasite studies examine pairwise interactions, meaning we still lack a general understanding of the influence of co-exposures and coinfections. Using the bumble bee Bombus impatiens, we study the effects of larval exposure to a microsporidian, Nosema bombi, implicated in bumble bee declines, and adult exposure to Israeli Acute Paralysis Virus (IAPV), an emerging infectious disease from honey bee parasite spillover. We hypothesize that infection outcomes will be modified by co-exposure or coinfection depending on relevant temporal interactions, due to changes in host immune allocation or condition. Nosema bombi is a potentially severe, larval-infecting parasite, and we predict that prior exposure will result in decreased host resistance to adult IAPV infection. We predict a double exposure will also reduce host tolerance, as measured by host survival. Although our larval Nosema exposure mostly did not result in viable infections, it reduced resistance to adult IAPV infection. Exposure to Nosema also negatively affected survival, potentially due to a cost of immunity in resisting the exposure. There was also a significant negative effect of IAPV exposure on survivorship, but in contrast to resistance, prior Nosema exposure did not alter this survival outcome. These results again demonstrate that infection outcomes within multi-parasite host networks can be non-independent, even when exposure to one parasite does not result in a substantial infection.

宿主-寄生虫相互作用并非孤立存在，而是发生于相互关联的多寄生虫网络之中。宿主个体一生中发生的共暴露与共感染，可对宿主健康及包括疾病暴发在内的传染病生态学特征产生影响。然而，当前多数宿主-寄生虫相关研究仅关注两两互作，这导致我们对共暴露与共感染的整体影响仍缺乏系统性认知。本研究以印刻熊蜂（Bombus impatiens）为实验对象，探究幼虫暴露于与熊蜂种群衰退相关的微孢子虫——熊蜂微孢子虫（Nosema bombi），以及成虫暴露于源自蜜蜂寄生虫溢出感染的新发传染病——以色列急性麻痹病毒（Israeli Acute Paralysis Virus, IAPV）所产生的影响。我们提出假说：由于宿主免疫分配或生理状态发生改变，共暴露或共感染对感染结局的调控作用将取决于二者的时序互作关系。熊蜂微孢子虫是一种可侵染幼虫的潜在致命寄生虫，我们预测，预先暴露于该寄生虫会降低宿主对成虫阶段IAPV感染的抵抗力。同时我们预测，双重暴露也会降低宿主的感染耐受性（以宿主存活率作为衡量指标）。尽管我们施加的幼虫阶段熊蜂微孢子虫暴露大多未形成可检测的有效感染，但该处理仍降低了宿主对成虫阶段IAPV感染的抵抗力。暴露于熊蜂微孢子虫也对宿主存活率产生了负面影响，这可能源于宿主为抵抗该寄生虫暴露所付出的免疫成本。IAPV暴露同样对宿主存活率存在显著负面影响，但与对感染抵抗力的影响不同，预先暴露于熊蜂微孢子虫并未改变这一存活结局。本研究结果再次证实，即便宿主仅暴露于某一种寄生虫且未形成显著感染，多寄生虫宿主网络内的感染结局也并非相互独立的。