Public‑Education Series：What‘s Artemisinin partial resistance？-

About AP-NDI

Public‑Education Series：What‘s Artemisinin partial resistance？

By Zheng Qi 2020-05-14

Artemisinin partial resistance, a growing public health concern first identified in Southeast Asia more than a decade ago, typically refers to a measurable delay in the clearance of malaria parasites from a patient’s bloodstream after they begin treatment with a standard Artemisinin-based Combination Therapy (ACT). In a fully responsive infection, the fast-acting artemisinin component of an ACT will rapidly reduce parasite levels, with most patients seeing their parasite counts drop dramatically within 48 hours. But in cases involving partial resistance, this process slows down noticeably: patients may still carry detectable numbers of parasites in their blood three days after starting treatment, a sign that the artemisinin compound is no longer as effective at wiping out all parasites within the recommended 3-day treatment window. This delayed clearance is not a trivial observation, as it means the infection lingers longer in the body, giving the remaining parasites more time to multiply and potentially spread further within the community, even if the patient does not immediately show severe new symptoms.

For many years, researchers around the world worked tirelessly to uncover exactly why and how these Plasmodium parasites were developing this reduced sensitivity to artemisinin, and their studies have now confirmed a critical, reassuring detail: the resistance mechanisms that the parasites have evolved to defend themselves against artemisinin compounds only impact one very specific stage of the malaria parasite’s life cycle inside the human body — the fragile, early ring stage. During this brief window after the parasite first invades a red blood cell, it is small, metabolically quiet, and far less vulnerable to the chemical attack of artemisinin than it is during later, more active stages of growth. This narrow, stage-limited effect is exactly why public health experts emphasize that the term “partial resistance” is the most accurate and responsible description for this phenomenon. The phrase deliberately highlights that this resistance is not total, that it only applies to a short, defined phase of the parasite’s development, and that artemisinin still retains its powerful killing effect on parasites in all other stages of their life cycle. To this day, scientists still do not know for certain whether artemisinin partial resistance could evolve further in the future, mutating in ways that allow it to affect other parasite stages and eventually develop into a complete, unbeatable resistance that renders artemisinin entirely useless. Crucially, however, no confirmed case of “full” artemisinin resistance has ever been officially documented anywhere in the world.

This partial, stage-specific nature of the resistance is also the reason that ACTs remain a highly effective tool even in regions where delayed parasite clearance has been detected. Currently, even when patients are infected with artemisinin partial resistant parasites, nearly every single one of them can still be fully cured by a standard ACT — as long as the partner drug paired with artemisinin in that specific formulation remains highly efficacious in their local geographical area. When the partner drug still works as intended, it can step in to eliminate all the parasites that the weakened artemisinin component could not clear in the first three days, finishing the job completely and preventing the infection from bouncing back. In situations where the partner drug itself has not developed resistance, artemisinin partial resistance very rarely leads to full treatment failure. Furthermore, after years of close monitoring in all the regions where partial resistance has been found, there is still no credible evidence that artemisinin partial resistance on its own has caused any measurable increase in malaria-related illness or death. This means that with careful surveillance, proper drug quality control, and continued efforts to preserve the effectiveness of partner drugs, the world can still protect the life-saving power of ACTs and avoid the catastrophic public health consequences that full artemisinin resistance would bring.

Edited by: Secretariat of the Asia-Pacific Network for Drug and Diagnostics Innovation
Produced by: Zheng Qi
Reviewed by: Zhang Haobing
Tel: 021-64377008-2510 Fax: 021-54108329
Address: 207 Ruijin 2nd Road, Huangpu District,Shanghai, P.R. China Postcode: 200025