How malaria parasites resist drugs, and why Kenya plans to rotate treatments

The World Health Organization (WHO) lists confirmed artemisinin partial resistance in Eritrea, Rwanda, Uganda and Tanzania, and says it is suspected in Ethiopia, Namibia, Sudan and Zambia. WHO defines it as a delay in clearing malaria parasites from the bloodstream.

The issue was discussed in Nairobi from 7 to 9 October. The Kenya Medical Research Institute (KEMRI), the Africa Centres for Disease Control and Prevention (Africa CDC), the East African Community (EAC) Secretariat, the Science for Africa Foundation and the RBM Partnership to End Malaria co-hosted a genomics pre-conference on 7 October and the second EAC Malaria Stakeholders' Meeting on 8 and 9 October, according to KEMRI. Participants asked for a standardised East African framework for genomic surveillance and data sharing, and for Pfk13 markers linked to artemisinin resistance to be monitored over time.

WHO says artemisinin-based combination therapies (ACTs), which combine an artemisinin derivative with a partner drug, are the most effective treatment for Plasmodium falciparum, the deadliest malaria parasite. Resistance here is partial because, in WHO's words, it affects only one stage of the parasite's life in humans, the ring stage.

WHO's question-and-answer page on resistance, dated 9 January 2025, says the role of the artemisinin compound is to reduce the number of parasites during the first three days of treatment; partial resistance means that clearance is delayed. Mutations in a parasite gene called PfKelch13, or K13, are used as markers. WHO lists a mutation as validated when, in at least 20 patients, it is statistically linked to a parasite clearance half-life of more than five hours or to parasites still in the blood on day three, and laboratory tests also support it. WHO says more than 260 such mutations have been reported, and not all are tied to resistance.

WHO also uses therapeutic efficacy studies (TES) to assess the efficacy of recommended ACTs: patients are treated and followed to see whether the drug clears the infection. Repeated studies at the same sites can show a decline early, WHO says. Kelvin Thiong'o, Head of the Malaria Department at KEMRI, is principal investigator for the malaria therapeutic efficacy studies, according to the institute's account of the Nairobi meeting.

WHO says the African parasites emerged independently and did not spread from South-East Asia. In a publication dated 20 November 2024, WHO says artemisinin partial resistance alone does not lead to ACT failure where the partner medicines are still effective. Its question-and-answer page describes ACTs as the best available treatment and says resistance should not make providers or patients hesitate to use them for confirmed malaria.

Kenya's response is a change in how drugs are chosen. The Star reported on 28 April that Kenya would adopt multiple first-line therapies (MFT) from October, with health workers rotating among several combinations, including artemether-lumefantrine, on which Kenya has largely depended for years, artesunate-pyronaridine and dihydroartemisinin-piperaquine. The National Malaria Control Programme cited early signs that parasites are beginning to adapt to current treatments in some parts of the country, the paper said.

In Siaya County, the effectiveness of artemether-lumefantrine fell from 97.8% in 2011 to 88.5% in 2017, according to The Star. Jhpiego, which implements a Unitaid-funded project on multiple first-line therapies, said in a post on 20 April that using several first-line treatments at the same time "puts less pressure on any one drug". The Ministry of Health's implementation plan covers 2026 to 2030 and was validated at a meeting on 5 February 2026, Jhpiego said.

Patients may receive different drugs on different visits. "Receiving different malaria medicines at different visits is expected and correct under MFT policy," Dr Edwin Onyango of the National Malaria Control Programme said, as quoted by The Star. He also said the change rests on emerging scientific evidence rather than a failure of current drugs, and that patients should complete the full dose as instructed. The rollout will begin in high-burden counties including Siaya, Kakamega, Busia, Kisumu and Migori before expanding nationwide, the paper said.

The Star reported that Kenya recorded about 4.2 million malaria cases in 2024, with the disease accounting for 18% of outpatient visits, and that about three in four Kenyans live in malaria-risk areas. It said the burden remains concentrated in western Kenya around Lake Victoria. WHO's fact sheet says the WHO African Region had about 95% of the world's 282 million estimated malaria cases in 2024.

WHO says the most common early symptoms are fever, headache and chills, and that getting tested early is important because some symptoms are not specific. Travellers to malaria areas should consult a doctor several weeks before departure, it says.

At the Nairobi meeting, Kenya, Rwanda and Tanzania shared their experience of putting multiple first-line therapies into practice, KEMRI said. Rotating treatments over two years was discussed as a way to preserve efficacy and delay resistance, with concern about added pressure on lumefantrine, the partner drug in artemether-lumefantrine. Participants proposed an EAC white paper on the evidence and policy for multiple first-line approaches, including options beyond ACTs. Dr Erick Lelo, who spoke for KEMRI's Vice Chancellor and CEO, told the meeting: "Malaria does not respect borders, and neither should our solutions."