Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
MIVEGEC (UMR CNRS 5290), Montpellier, France.
Proc Biol Sci. 2020 Nov 25;287(1939):20202615. doi: 10.1098/rspb.2020.2615.
A pervasive characteristic of parasite infections is their tendency to be overdispersed. Understanding the mechanisms underlying this overdispersed distribution is of key importance as it may impact the transmission dynamics of the pathogen. Although multiple factors ranging from environmental stochasticity to inter-individual heterogeneity may explain parasite overdispersion, parasite infection is also overdispersed in an inbred host population maintained under laboratory conditions, suggesting that other mechanisms are at play. Here, we show that the aggregated distribution of malaria parasites within mosquito vectors is partially explained by a temporal heterogeneity in parasite infectivity triggered by the bites of mosquitoes. Parasite transmission tripled between the mosquito's first and last blood feed in a period of only 3 h. Surprisingly, the increase in transmission is not associated with an increase in parasite investment in production of the transmissible stage. Overall, we highlight that is capable of responding to the bites of mosquitoes to increase its own transmission at a much faster pace than initially thought and that this is partly responsible for overdispersed distribution of infection. We discuss the underlying mechanisms as well as the broader implications of this plastic response for the epidemiology of malaria.
寄生虫感染的一个普遍特征是它们倾向于过度离散。理解这种过度离散分布的机制至关重要，因为它可能影响病原体的传播动态。尽管从环境随机性到个体间异质性的多种因素都可以解释寄生虫的过度离散，但在实验室条件下维持的近交宿主群体中，寄生虫感染也存在过度离散，这表明存在其他机制在起作用。在这里，我们表明，蚊子载体中疟原虫的聚集分布部分是由蚊子叮咬引起的寄生虫感染力的时间异质性所解释的。在仅仅 3 小时的时间内，蚊子的第一次和最后一次吸血之间，寄生虫的传播增加了两倍。令人惊讶的是，传播的增加与寄生虫在可传播阶段的生产中投入的增加无关。总的来说，我们强调指出，疟原虫能够对蚊子的叮咬做出反应，以比最初想象的更快的速度增加自身的传播，这是感染过度离散分布的部分原因。我们讨论了这种可塑性反应的潜在机制以及对疟疾流行病学的更广泛影响。
