Data from: Costs of crowding for the transmission potential in malaria parasites

The utility of using evolutionary and ecological frameworks to understand the dynamics of infectious diseases is gaining increasing recognition. However, integrating evolutionary ecology and infectious disease epidemiology is challenging because within-host dynamics can have counterintuitive consequences for between-host transmission, especially for vector-borne parasites. A major obstacle to linking within- and between-host processes is that the drivers of the relationships between the density, virulence, and fitness of parasites are poorly understood. By experimentally manipulating the intensity of rodent malaria (Plasmodium berghei) infections in Anopheles stephensi mosquitoes under different environmental conditions, we show that parasites experience substantial density-dependent fitness costs because crowding reduces both parasite proliferation and vector survival. We then use our data to predict how interactions between parasite density and vector environmental conditions shape within-vector processes and onward disease transmission. Our model predicts that density-dependent processes can have substantial and unexpected effects on the transmission potential of vector-borne disease, which should be considered in the development and evaluation of transmission-blocking interventions.

利用进化与生态学框架解析传染病动态的研究价值正日益获得学界认可。然而，整合进化生态学与传染病流行病学仍存在显著挑战：宿主体内动态对宿主间传播可能产生反直觉的影响，针对媒介传播寄生虫的研究尤为如此。制约宿主体内与宿主间过程关联研究的一大核心障碍，是学界对寄生虫密度、毒力与适合度之间关系的驱动机制仍知之甚少。本研究通过在不同环境条件下，对斯氏按蚊（Anopheles stephensi）体内的啮齿类疟疾——伯氏疟原虫（Plasmodium berghei）——感染强度开展实验调控，证实寄生虫会承受显著的密度依赖型适合度代价：种群拥挤会同时抑制寄生虫增殖并降低媒介昆虫的存活率。随后，本研究利用实验数据，预测了寄生虫密度与媒介环境条件之间的交互作用如何塑造媒介体内过程与后续疾病传播态势。本研究构建的模型显示，密度依赖过程会对媒介传播疾病的传播潜力产生显著且出乎意料的影响，这一发现应在阻断传播干预措施的开发与评估中予以充分考量。