Data from: The fitness of drug-resistant malaria parasites in a rodent model: multiplicity of infection

Malaria infections normally consist of more than one clonally-replicating lineage. Within-host interactions between sensitive and resistant parasites can have profound effects on the evolution of drug resistance. Here, using the Plasmodium chabaudi mouse malaria model, we ask whether the costs and benefits of resistance are affected by the number of co-infecting strains competing with a resistant clone. We found strong competitive suppression of resistant parasites in untreated infections and marked competitive release following treatment. The magnitude of competitive suppression depended on competitor identity. However, there was no overall effect of the diversity of susceptible parasites on the extent of competitive suppression or release. If these findings generalize, then transmission intensity will impact on resistance evolution because of its effect on the frequency of mixed infections, not because of its effect on the distribution of clones per host. This would greatly simplify the computational problems of adequately capturing within-host ecology in models of drug resistance evolution in malaria.

疟疾感染通常包含不止一种克隆复制谱系。宿主内敏感与耐药疟原虫间的相互作用，可对耐药性演化产生深远影响。本研究依托查氏疟原虫（Plasmodium chabaudi）小鼠疟疾模型，探究与耐药克隆竞争的共感染菌株数量，是否会影响耐药性的成本与收益。研究发现，未接受治疗的感染中存在显著的耐药疟原虫竞争性抑制，而治疗后则出现明显的竞争性释放。竞争性抑制的强度取决于竞争菌株的种类。然而，易感疟原虫的多样性并未对竞争性抑制或释放的程度产生整体影响。若该研究结论具有普适性，则传播强度会通过影响混合感染的发生频率，而非影响每个宿主内的克隆分布，进而对耐药性演化产生作用。这将极大简化疟疾耐药性演化模型中，精准刻画宿主内生态所需的计算难题。