Daily rhythms of Plasmodium chabaudi, showing that 60% of those are intrinsic to the parasite

Malarial rhythmic fevers are the consequence of the synchronous bursting of red blood cells (RBCs) upon completion of the malaria parasite asexual cell-cycle. Here we hypothesized that an intrinsic clock in the parasite underlies the modulo-24h rhythms of RBC bursting. We show that parasite rhythms are plastic and slow down to match rhythms of hosts with long circadian period. We also demonstrate that malaria rhythms persist even when host food intake is evenly spread across 24h, suggesting that host feeding cues are not required for synchrony. Moreover, we find that the parasite population remains synchronous and rhythmic even in an arrhythmic clock mutant host. Thus, we propose that parasite rhythms are generated by the parasite, possibly to anticipate its rhythmic changing environment. Overall design: mRNA-seq circadian profiles were generated from Plasmodium chabaudi infected mouse blood. Multiple host conditions tested, from normal light/dark cycles, complete darkness, long period mutants, spread-out feeding and arrhythmic mutants