Genetic diversity and dynamics of Plasmodium falciparum and P-vivax populations in multiply infected children with asymptomatic malaria infections inPapua New Guinea

We describe the dynamics of co-infections of Plasmodium falciparum and P. v ivax in 28 asymptomatic children by genotyping these species using the poly morphic loci Msp2 and Msp3 alpha, respectively. The total number of Plasmod ium spp. infections detected using 3 day sampling over 61 days varied betwe en 1 and 14 (mean 6.6). The dynamics of P. falciparum and P. vivax genotype s varied greatly both within and amongst children. Periodicity in the detec tion of P. falciparum infections is consistent with the synchronous replica tion of individual genotypes. Replication synchrony of multiple coinfecting genotypes was not detected. In 4-year-old children P. falciparum genotype complexity was reduced and episodes lasted significantly longer (median dur ation > 60 days) when compared to children aged 5-14 years (median duration 9 days). P. vivax genotype complexity was not correlated with age but the episode duration was also longer for this species in 4-year-olds than in ol der children but was not as long as P. falciparum episodes. Recurrence of P . falciparum and P. vivax genotypes over weeks was observed. We interpret t hese major fluctuations in the density of genotypes over time as the result of the mechanism of antigenic variation thought to be present in these Pla smodium species.