Also we should understand that
After a person is infected with Plasmodium parasites through the bite of an infected mosquito, the parasites first migrate to the liver, where they undergo an incubation period (typically 7–14 days, depending on the species). During this hepatic phase, the parasites multiply and develop into tissue schizonts, which later rupture to release merozoites into the bloodstream.
These merozoites are the infective blood-stage forms that invade red blood cells, digest haemoglobin (globin), multiply further, and cause the classical symptoms of malaria such as fever, headache, malaise, chills, and body pain.
In some malaria species, most notably Plasmodium vivax and Plasmodium ovale a proportion of liver-stage parasites do not immediately mature. Instead, they remain dormant in the liver as hypnozoites (often mistakenly referred to as “dormant schizonts”). These dormant forms can reactivate weeks or even months later, causing relapse, even in the absence of a new mosquito bite.
Most conventional antimalarial treatments, including many artemisinin-based combination therapies (ACTs), primarily target the blood-stage parasites (merozoites). This is logical because these forms are responsible for the symptoms that bring patients to the clinic. However, standard ACTs do not eliminate dormant liver forms (hypnozoites).
This explains why some individuals experience recurrent malaria episodes after apparently successful treatment. Factors such as stress, reduced immunity, intercurrent illness, or alcohol consumption may coincide with relapse, leading people to believe these factors “caused” the malaria, when in reality they triggered the reactivation of dormant parasites.
ACTs combine a fast-acting artemisinin derivative (artemether, artesunate, dihydroartemisinin, etc.) with a longer-acting partner drug. These partner drugs remain in the bloodstream after the artemisinin component has been cleared and help eliminate residual blood-stage parasites.
However, most ACT partner drugs do not effectively target liver hypnozoites.
It is important to clarify that hypnozoites are not formed by Plasmodium falciparum. Dormant liver-stage hypnozoites are a defining feature of P. vivax and P. ovale infections.
However, Plasmodium falciparum may persist at very low levels in the blood, sometimes described as drug-tolerant or persister ring-stage parasites, which can lead to recrudescence (not true relapse), particularly if blood-stage clearance is incomplete after treatment.
Crucially, only the 8-aminoquinoline class of antimalarials, notably primaquine and tafenoquine has proven activity against dormant liver hypnozoites. These drugs are essential for achieving radical cure and preventing relapse in P. vivax and P. ovale infections.
Because of persistent or recurrent infections, some clinicians use adjunct antimalarial agents, such as:
Sulfadoxine–pyrimethamine (Fansidar)
Doxycycline
Clindamycin
Atovaquone–proguanil
These agents help suppress or clear blood-stage parasites and improve treatment efficacy, but they do not reliably eliminate dormant liver hypnozoites, further underscoring the importance of 8-aminoquinolines for true relapse prevention.
Key points to note:-
Relapse—hypnozoites (P. vivax, P. ovale)
Recrudescence—persistent blood-stage parasites (P. falciparum)
WHY YOUR MALARIA TREATMENT ISN'T WORKING
If you treat malaria every 1-2 months and the symptoms keep coming back, there's a problem.
It could be a wrong diagnosis, incomplete treatment, or reinfection.
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