Plasmodium vivax and P. ovale are the species associated with malaria recurrence after treatment
Both P. vivax (Option B) and P. ovale (Option D) cause recurrent malaria due to dormant liver-stage hypnozoites that reactivate weeks to months after initial treatment, but P. vivax is by far the most common cause of recurrence globally.
Why P. vivax and P. ovale Cause Recurrence
The unique feature distinguishing these species is the presence of hypnozoites—dormant liver-stage parasites that persist after blood-stage treatment 1. These hypnozoites can reactivate to cause relapses:
- P. vivax: Relapses occur in up to 81% of patients within 90 days, with median time to first relapse of 20 days 2
- P. ovale: First-time relapse occurs in 4.1% of episodes (lower than vivax) 1
- A Swedish retrospective study showed 9.3% relapse rate for P. vivax and 4.1% for P. ovale 1
Why Not P. falciparum or P. malariae?
- P. falciparum (Option A): Does not form hypnozoites; recurrences represent treatment failure or reinfection, not true relapse 1
- P. malariae (Option C): Can cause recrudescence from persistent low-level blood-stage parasitemia (not hypnozoites), but this is rare and occurs over years, not the typical pattern of "recurrence after treatment" 1
Clinical Implications
Following blood-stage treatment, patients with P. vivax or P. ovale require anti-relapse therapy with primaquine or tafenoquine to eradicate hypnozoites 1. Without this radical cure:
- Primaquine reduces relapse risk by 80% 1
- Recurrent infections maintain transmission even when asymptomatic 3
- Most relapses (71%) are asymptomatic but remain infectious to mosquitoes 3, 2
Critical Caveat
G6PD testing is mandatory before administering primaquine or tafenoquine due to hemolysis risk 1. Both drugs are contraindicated in pregnancy 1.
Answer to the Question
If forced to choose a single answer: B) Vivax is correct, as it is the most common species causing recurrence globally and accounts for the majority of relapse cases in endemic regions 1, 4, 2.
However, D) Ovale is also technically correct, as it shares the same hypnozoite-mediated relapse mechanism 1. The question's phrasing "reports show an increase in recurrence" most strongly suggests P. vivax given its higher frequency and the substantial body of recent evidence documenting frequent relapses 4, 3, 2.