Malaria parasites and circadian rhythm: New insights into an old puzzle
The hallmark of #malaria, an infectious disease caused by parasites from the Plasmodium genus, is cyclic fever. Fevers and chills generally occur within 48 h (h) for Plasmodium falciparum (Fig. 1A) and Plasmodium vivax and every 72 h for Plasmodium malariae. This periodic fever has been known for almost a century to be a consequence of synchronous maturation of the parasites inside the host erythrocytes followed by the rupture of infected cells and the massive release of parasites into the bloodstream (Garcia et al., 2001; Stauber, 1939; Taliaferro, 1925). In the 1970s, Hawking observed that many Plasmodium species follow multiple 24-h life cycles in the vertebrate host, suggesting that the malaria parasite has a circadian rhythm (Hawking, 19701975). The circadian rhythm functions as an internal oscillator that repeats approximately every 24 h inside an organism; this rhythm is controlled by an external stimulus, such as a photoperiod, and is responsible for synchronizing behavioral and physiological rhythms (Rusak and Zucker, 1975).