Relapsing malaria is associated with P. vivax and P. ovale due to relapse after initial illness; which two species demonstrate this pattern?

• A. P. vivax and P. ovale
• B. P. falciparum and P. vivax
• C. P. malariae and P. knowlesi
• D. P. vivax and P. malariae

Answer: (A)

Relapsing malaria happens when parasites hide in the liver as dormant forms and reactivate later, causing new clinical illness without a new mosquito bite. The species that form these dormant liver stages are P. vivax and P. ovale. After the initial infection, some parasites remain in hepatocytes as hypnozoites and can awaken weeks or months afterward, leading to another fever pattern. This is different from relapses caused by persistent blood-stage parasites (recrudescence) or new infections.

So, the relapsing pattern is characteristic of P. vivax and P. ovale because of their ability to form and reactivate hepatic hypnozoites.