Parasitological efficacy of seasonal malaria chemoprevention in Nampula, northern Mozambique

BACKGROUND: Deployment of seasonal malaria chemoprevention (SMC) for young children using monthly sulphadoxine-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 d after first SPAQ administration. RESULTS: After SPAQ, parasitaemia prevalence decreased from 68% to 41%. Among children followed successfully for 28 d, malaria parasitaemia prevalence declined from 71% to 44%. Preventive efficacy was 97% for Plasmodium ovale and 42% 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.