Comparative population structure of Plasmodium malariae and Plasmodium falciparum under different transmission settings in Malawi

Malaria Journal

Research

Marian C Bruce¹  Malcolm E Molyneux²  Allan Macheso³  Alex McConnachie⁴ 

[1] Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Level 5, Glasgow Biomedical Research Centre, Glasgow University, 120 University Place, Glasgow University of Glasgow, G12 8TA, UK;Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi, and School of Tropical Medicine, University of Liverpool, UK;Ministry of Health and Population, Government of Malawi, currently at Management Sciences for Health Malawi Programme, Lilongwe, Malawi;Robertson Centre for Biostatistics, Boyd Orr Building, Glasgow University, University Avenue, G12 8QQ, Glasgow, UK;

关键词: Malaria;    Plasmodium;    Parasite Density;    Plasmodium Species;    Clinical Malaria;   

DOI  :  10.1186/1475-2875-10-38

 received in 2010-08-10, accepted in 2011-02-11,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundDescribed here is the first population genetic study of Plasmodium malariae, the causative agent of quartan malaria. Although not as deadly as Plasmodium falciparum, P. malariae is more common than previously thought, and is frequently in sympatry and co-infection with P. falciparum, making its study increasingly important. This study compares the population parameters of the two species in two districts of Malawi with different malaria transmission patterns - one seasonal, one perennial - to explore the effects of transmission on population structures.MethodsSix species-specific microsatellite markers were used to analyse 257 P. malariae samples and 257 P. falciparum samples matched for age, gender and village of residence. Allele sizes were scored to within 2 bp for each locus and haplotypes were constructed from dominant alleles in multiple infections. Analysis of multiplicity of infection (MOI), population differentiation, clustering of haplotypes and linkage disequilibrium was performed for both species. Regression analyses were used to determine association of MOI measurements with clinical malaria parameters.ResultsMultiple-genotype infections within each species were common in both districts, accounting for 86.0% of P. falciparum and 73.2% of P. malariae infections and did not differ significantly with transmission setting. Mean MOI of P. falciparum was increased under perennial transmission compared with seasonal (3.14 vs 2.59, p = 0.008) and was greater in children compared with adults. In contrast, P. malariae mean MOI was similar between transmission settings (2.12 vs 2.11) and there was no difference between children and adults. Population differentiation showed no significant differences between villages or districts for either species. There was no evidence of geographical clustering of haplotypes. Linkage disequilibrium amongst loci was found only for P. falciparum samples from the seasonal transmission setting.ConclusionsThe extent of similarity between P. falciparum and P. malariae population structure described by the high level of multiple infection, the lack of significant population differentiation or haplotype clustering and lack of linkage disequilibrium is surprising given the differences in the biological features of these species that suggest a reduced potential for out-crossing and transmission in P. malariae. The absence of a rise in P. malariae MOI with increased transmission or a reduction in MOI with age could be explained by differences in the duration of infection or degree of immunity compared to P. falciparum.

【 授权许可】

CC BY   
© Bruce et al; licensee BioMed Central Ltd. 2011