Parasitological efficacy of seasonal malaria chemoprevention in Nampula, northern Mozambique

Authors: Craig Bonnington, Mercia Sitoe, Ivan A Pulido Tarquino, Sonia M Enosse, Chayanin Sararat, Kanokorn Suwannasin, Stephane Proux, Urairat Koesukwiwat, Joel Tarning, Mallika Imwong, Katherine Theiss-Nyland, François Henri Nosten, Nicholas John White

A high level of parasitological chemoprevention failure following seasonal malaria chemoprevention with sulfadoxine-pyrimethamine plus amodiaquine (SPAQ) in two areas of northern Mozambique could not be explained adequately by known drug resistance markers.

Background
Deployment of seasonal malaria chemoprevention (SMC) for young children using monthly sulfadoxine-pyrimethamine-amodiaquine (SPAQ) has recently been extended to Central and East Africa.

Methods
A pilot pharmacometric assessment was nested within a larger deployment of SMC in a high malaria transmission area in northern Mozambique. SPAQ was given to 460 healthy children in two large villages. Simultaneous filter-paper blood spot malaria quantitative PCRs, blood slide microscopy and antimalarial drug measurements were taken before, then 7 and 28 days after first SPAQ administration.

Results
After SPAQ, parasitaemia prevalence decreased from 68 percent to 41 percent. Among children followed successfully for 28 days, malaria parasitaemia prevalence declined from 71 percent to 44 percent. Preventive efficacy was 97 percent for Plasmodium ovale and 42 percent for Plasmodium falciparum. Reinfections (N=50 with sufficient DNA for genotyping) and recrudescences (N=3) often grew through high concentrations of desethylamodiaquine, yet all 250 P. falciparum isolates genotyped were Pfcrt 76K, a molecular marker of 4-aminoquinoline susceptibility. One-third (21/64) of microscopy-detectable breakthrough P. falciparum infections had patent gametocytaemia. There was a clear chemoprevention exposure–response relationship evident for desethylamodiaquine, but not for sulphadoxine or pyrimethamine.

Conclusions
In Nampula, northern Mozambique, amodiaquine had low parasitological efficacy and sulphadoxine and pyrimethamine did not contribute significantly to chemoprevention.

Citation: Transactions of The Royal Society of Tropical Medicine and Hygiene, 2026; 120(3): 258–267,