Parasitology



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


M. C. BRUCE a1c1, M. R. GALINSKI a2, J. W. BARNWELL a3, C. A. DONNELLY a1, M. WALMSLEY a4, M. P. ALPERS a5, D. WALLIKER a4 and K. P. DAY a1
a1 Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, Oxford OX1 3FY
a2 Department of Medicine, Division of Infectious Diseases, Emory University School of Medicine, Emory Vaccine Center, Atlanta, GA 30329, USA
a3 Biology and Diagnostic Branch, Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
a4 Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JN
a5 Papua New Guinea Institute of Medical Research, P.O. Box 378, Madang, Papua New Guinea

Abstract

We describe the dynamics of co-infections of Plasmodium falciparum and P. vivax in 28 asymptomatic children by genotyping these species using the polymorphic loci Msp2 and Msp3α, respectively. The total number of Plasmodium spp. infections detected using 3 day sampling over 61 days varied between 1 and 14 (mean 6·6). The dynamics of P. falciparum and P. vivax genotypes varied greatly both within and amongst children. Periodicity in the detection of P. falciparum infections is consistent with the synchronous replication of individual genotypes. Replication synchrony of multiple co- infecting genotypes was not detected. In 4-year-old children P. falciparum genotype complexity was reduced and episodes lasted significantly longer (median duration > 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 older children but was not as long as P. falciparum episodes. Recurrence of P. falciparum and P. vivax genotypes over weeks was observed. We interpret these major fluctuations in the density of genotypes over time as the result of the mechanism of antigenic variation thought to be present in these Plasmodium species.

(Received November 9 1999)
(Revised March 16 2000)
(Accepted March 16 2000)


Key Words: Plasmodium falciparum; Plasmodium vivax; dynamics; asymptomatic infection; genotyping.

Correspondence:
c1 Corresponding author: Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, Oxford OX1 3FY. Tel: +01865 271247. Fax: +01865 281245. E-mail: marianbruce@hotmail.com


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