• Incidence of malaria [ Time Frame: Four months ]
  

• Adverse events reported by the mother: vomiting, headache, fever, nausea, diarrhea [ Time Frame: within 4 days of the start treatment ]
  
• Prevalence of P.falciparum parasitaemia [ Time Frame: Measured by microscopy 1 month after the last treatment, in December ]
  
• Haemoglobin concentration [ Time Frame: Measured 1 month after the last treatment, in December ]
  
• The proportion of children carrying P.falciparum genotypes associated with resistance to sulfadoxine and pyrimethamine [ Time Frame: Measured in December ]
  
• Compliance with the treatment regimen [ Time Frame: Recorded 4 days after the start of treatment ]
  

In areas of seasonal malaria transmission the burden of severe disease and mortality due to malaria is mainly among children under 5 years of age. Intermittent preventive treatment (IPT) with antimalarial drugs given to all children once a month during the transmission season is a promising new strategy for malaria prevention. Seasonal IPT with sulfadoxine-pyrimethamine (SP) and one dose of artesunate resulted in a 90% reduction in incidence of clinical malaria in a recent trial in Senegal (Cisse et al., Lancet 2006). An important consideration is the possible impact of seasonal IPT on the emergence and spread of drug resistant parasite genotypes, the choice of drug regimen is therefore critical. A second trial in Senegal showed that a combination of two non-artemisinin drugs with relatively long half lives (SP and amodiaquine (AQ) over three days) was more effective than SP with artesunate and more effective than AQ with artesunate, in preventing malaria; and very few children developed parasitaemia, so that the potential for drug resistant genotypes to emerge and spread was low. Although SP+AQ was more efficacious than the artemisinin-containing regimens tested, it was associated with a higher frequency of adverse events, especially vomiting, and AQ has a bitter unpleasant taste, and therefore we have concerns about the acceptability of AQ for widespread use for IPT. It is important to select a drug regimen that is not only effective but safe and acceptable to the community. Each treatment is a 3-dose regimen over 3 days, the first dose will be supervised and the other 2 doses given by the mother or carer. One month after each treatment round, children will be visited at home to check for malaria symptoms, children with fever or a history of fever in the last 48 hours will be asked to give a finger prick blood sample for malaria diagnosis. One month after the last treatment all children will be asked to give a finger prick blood sample for parasitology and haemoglobin, axillary temperature will be measured. The child's carer will be interviewed about compliance and adverse events. The endpoints will be the cumulative incidence of malaria, the proportion of children experiencing moderate and severe adverse events, compliance with and acceptability of the regimen, the prevalence of parasitaemia, and the proportion of children carrying parasite genotypes associated with resistance to sulfadoxine or pyrimethamine at the end of the transmission season. Since acceptability is difficult to assess in the formal setting of a trial, and because the method of delivery may affect compliance and acceptability, drug treatments will be delivered by community workers replicating the conditions under IPT would be delivered routinely in Senegal. Treatments will be administered at home by local community workers, each worker covering a circuit of approximately 60-80 children. The community worker circuit will be the unit of randomization, for simplicity in the field to minimise allocation errors, and to avoid contamination due to sharing of tablets within a household.