Seasonal malaria chemoprevention effectiveness and drug resistance in Plasmodium falciparum: a matched parallel cohort study, Kenya.

Authors

Beatrice Rotich, Emmah Kimachas, Joseph Kipkoech, Erastus Kirwa, Christine Markwalter, David Ekai, Ann Mwangi, Suzanne Van Hulle, Diana Menya, Wendy Prudhomme O'Meara

Published in

Bulletin of the World Health Organization. Volume 104. Issue 10. Pages 662-672. Oct 01, 2026. Epub Sep 01, 2026.

Abstract

To evaluate seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine in a semi-nomadic community in north-western Kenya, and to examine the relationship between parasite resistance and breakthrough infections.
A parallel cohort study conducted during the peak malaria season in 2024 involved 10 randomly selected villages in Turkana Central subcounty, where children younger than 5 years received seasonal malaria chemoprevention, and 10 matched villages in Turkana North subcounty (non-intervention cohort). We conducted surveillance of malaria symptoms weekly. The primary outcome was malaria-like symptoms plus a positive rapid diagnostic test result. We analysed Plasmodium falciparum genomic DNA in dried blood spot samples from children with symptomatic infections to identify pfdhfr and pfdhps gene substitutions associated with sulfadoxine-pyrimethamine resistance.
Children (198 in the intervention cohort and 200 in the non-intervention cohort) were followed until four weeks after the last chemoprevention cycle. In the intervention cohort, 72% (143/198) completed all five cycles. The incidence of malaria was significantly lower in the intervention than non-intervention cohort (adjusted incidence rate ratio 0.29; 95% confidence interval: 0.13-0.67). Plasmodium falciparum genomic DNA analysis of samples from 68 infected children showed that pfdhps gene mutations were more common in the intervention than non-intervention cohort and became more frequent as the number of treatment cycles increased.
Seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine was associated with substantial protection against malaria in children in an area where sulfadoxine-pyrimethamine resistance was common. Treated children were more likely to harbour resistant parasites.

PMID:
42819667
Bibliographic data and abstract were imported from PubMed on 02 Oct 2026.

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