Data from: The effects of sub-curative praziquantel treatment on life-history traits and trade-offs in drug-resistant Schistosoma mansoni

Natural selection acts on all organisms, including parasites, to maximise reproductive fitness. Drug resistance traits are often associated with life-history costs in the absence of treatment. Schistosomiasis control programmes rely on mass drug administration to reduce human morbidity and mortality. Although hotspots of reduced drug efficacy have been reported, resistance is not widespread. Using Bayesian State-Space Models (SSMs) fitted to data from an in vivo laboratory system, we tested the hypothesis that the spread of resistant Schistosoma may be limited by life-history costs not present in susceptible counterparts. Schistosoma mansoni parasites from a praziquantel–susceptible (S), a praziquantel–resistant (R) or a mixed line of originally resistant and susceptible parasites (RS) were exposed to a range of praziquantel doses. Parasite numbers at each life stage were quantified in their molluscan intermediate and murine definitive hosts across four generations, and SSMs were used to estimate key life-history parameters for each experimental group over time. Model outputs illustrated that parasite adult survival and fecundity in the murine host decreased across all lines, including R, with increasing drug pressure. Trade-offs between adult survival and fecundity were observed in all untreated lines, and these remained strong in S with praziquantel pressure. In contrast, trade-offs between adult survival and fecundity were lost under praziquantel pressure in R. As expected, parasite life-history traits within the molluscan host were complex, but trade-offs were demonstrated between parasite establishment and cercarial output. The observed trade-offs between generations within hosts, which were modified by praziquantel treatment in the R line, could limit the spread of R parasites under praziquantel pressure. Whilst such complex life-history costs may be difficult to detect using standard empirical methods, we demonstrate that SSMs provide robust estimates of life history parameters, aiding our understanding of costs and trade-offs of resistant parasites within this system and beyond.

自然选择作用于所有生物（包括寄生虫），以最大化其繁殖适合度。在无药物处理的情况下，抗药性性状通常与生活史代价相关联。血吸虫病（Schistosomiasis）防控方案依靠大规模药物给药以降低人类的发病率与死亡率。尽管已有报道称存在药物疗效下降的热点区域，但抗药性并未广泛传播。本研究利用适配于体内实验室系统数据的贝叶斯状态空间模型（Bayesian State-Space Models, SSMs），验证了这一假说：抗药性血吸虫的传播可能受到敏感品系所不具备的生活史代价的限制。
本研究使用的曼氏血吸虫（Schistosoma mansoni）分为吡喹酮（praziquantel）敏感株（S）、吡喹酮（praziquantel）抗药性株（R）以及由原始抗药性与敏感株混合得到的混合株（RS），将其暴露于一系列梯度剂量的吡喹酮环境中。研究在四代实验周期内，分别对其软体动物中间宿主与啮齿类终宿主体内各生活阶段的寄生虫数量进行定量，并利用SSMs随时间推移估算每个实验组的关键生活史参数。
模型结果显示，随着药物压力升高，包括R株在内的所有品系的曼氏血吸虫在啮齿类宿主内的成虫存活率与繁殖力均出现下降。所有未处理组均观察到成虫存活率与繁殖力之间存在权衡关系，且在S株受吡喹酮药物压力时，该权衡关系依然显著。与之相反，R株在吡喹酮药物压力下，成虫存活率与繁殖力之间的权衡关系消失。
正如预期，软体动物宿主内的血吸虫生活史特征较为复杂，但研究证实其宿主建立能力与尾蚴产出量之间存在权衡关系。本研究观察到宿主内不同世代间的权衡关系，且该关系在R株中受吡喹酮处理影响发生改变，这一现象可限制R株在吡喹酮药物压力下的传播。
尽管利用标准实验方法难以检测此类复杂的生活史代价，但本研究证实SSMs可对生活史参数提供稳健的估算结果，有助于我们理解该系统乃至其他系统中抗药性寄生虫的代价与权衡关系。