The epidemiology of multiple Plasmodium falciparum infections - 8. Effect of iron supplementation and malaria prophylaxis in infants on Plasmodium falciparum genotypes and multiplicity of infection

During a randomized placebo-controlled trial of chemoprophylaxis against Pl asmodium falciparum malaria and iron supplementation, in infants living und er conditions of intense transmission, all samples of P. falciparum obtaine d from children aged 5 and 8 months were genotyped by polymerase chain reac tion-restriction fragment length polymorphism analysis for the msp2 locus. One hundred and six blood samples were analysed for the number of concurren t infections (multiplicity), and the allelic family of each msp2 genotype w as determined. Mean multiplicity of infection was, overall, 2.76 infections /child, and it was significantly reduced in infants receiving chemoprophyla xis. This finding might help to explain the rebound effect in morbidity obs erved after prophylaxis was ended. Iron supplementation did not affect mult iplicity of infection. In infants receiving placebo only, or placebo and ir on supplementation, a significant positive association was observed between the number of infections and parasite densities (Spearman's rho=0.25, P-0. 047). This association was lost in the group receiving chemoprophylaxis alo ne, or in combination with iron. This study showed a significant associatio n of FC27-like msp2 alleles with prospective risk of clinical malaria in ch ildren (relative risk=1.487, P=0.013). Such an association was also found f or the present risk of clinical malaria in infants receiving prophylaxis (o dds ratio=3.84, P=0.026), which might imply that chemoprophylaxis may impai r the development of premunition.