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Why does Plasmodium malariae malaria have a 72-hour fever cycle?

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Malaria life cycle — malaria Life cycle of a malaria parasite.

The 72-hour fever cycle associated with Plasmodium malariae, often referred to as quartan malaria, is a direct result of the parasite's specific biological life cycle within the human host.12

After infecting red blood cells, the parasites grow and divide into a new generation of merozoites. The interval between the initial invasion of a red blood cell and the subsequent rupture of that cell—which releases the new generation of merozoites into the bloodstream—is approximately 72 hours for P. malariae.21

The characteristic chills and fever occur because the destruction of these red blood cells liberates toxins into the host's system. Consequently, the periodic fever attacks coincide with the synchronized release of each new generation of parasites. While other species like P. vivax and P. falciparum have a 48-hour cycle, the slower developmental pace of P. malariae results in the longer 72-hour interval between these symptomatic events.12