Which subtype of malaria is most likely to cause recurrence of pre-existing malaria?

The most likely subtype of malaria to cause recurrence of pre-existing malaria is Plasmodium vivax. This is primarily due to its unique lifecycle, which includes the ability to form hypnozoites, a dormant stage that can remain in the liver for extended periods. These hypnozoites can reactivate, leading to relapses of the disease after the initial infection has been cleared from the bloodstream.

Plasmodium vivax can remain asymptomatic for a long time, and the relapses can occur weeks to months after the initial infection, making it distinct from other malaria species. Effective treatment requires not only addressing the infection circulating in the blood but also targeting these dormant liver forms, typically necessitating additional medications like primaquine that specifically work against hypnozoites.

In contrast, other malaria species such as Plasmodium falciparum, while more severe and commonly associated with acute infections and complications, do not exhibit this dormant liver stage and therefore do not cause recurrences in the same way. Plasmodium malariae and Plasmodium ovale also have their respective characteristics but lack the same propensity for relapse as seen with Plasmodium vivax.