Diversity of Plasmodium falciparum populations and complexity of infections in relation to transmission intensity and host age: a study from the Usambara Mountains, Tanzania

• Published in: Transactions of the Royal Society of Tropical Medicine and Hygiene Vol. 95; no. 2; pp. 143 - 148
• Main Authors: Bendixen, M., Msangeni, H.A., Pedersen, B.V., Shayo, D., Bedker, R.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2001; Royal Society of Tropical Medicine and Hygiene; Elsevier
• Subjects: Adolescent; Adult; age; Age Distribution; Aged; Altitude; Animals; Antigens, Protozoan - genetics; Biological and medical sciences; Child; Child, Preschool; Cross-Sectional Studies; genetic diversity; Genetic Variation; Human protozoal diseases; Humans; Infant; Infant, Newborn; Infectious diseases; Malaria; Malaria, Falciparum - epidemiology; Malaria, Falciparum - genetics; Malaria, Falciparum - transmission; Medical sciences; Merozoite Surface Protein 1 - genetics; Middle Aged; msp-1; msp-2; multiple infection; Parasitic diseases; Plasmodium falciparum; Plasmodium falciparum - genetics; Polymerase Chain Reaction - methods; Protozoal diseases; Protozoan Proteins - genetics; Regression Analysis; Sensitivity and Specificity; Tanzania; Tanzania - epidemiology; transmission intensity; Tropical medicine; Africa; Tanzania; Plasmodium falciparum; genetic diversity; Tanzania; multiple infection; msp-2; msp-1; malaria; transmission intensity; age; Human; Protozoa; Apicomplexa; Protozoal disease; Malaria; Transmission; Genotype; Genetic diversity; Parasitosis; Infection; Polymerase chain reaction; Merozoite; Age
• ISSN: 0035-9203; 1878-3503
• DOI: 10.1016/S0035-9203(01)90140-3

Diversity and complexity of infections with
Plasmodium falciparum were described from cross-sectional surveys in November–December 1996 in 6 villages in the Usambara Mountains, Tanzania, where transmission ranged markedly from 0·03 to 91 infective bites per individual per year. Forty-eight samples, stratified for age and parasite densities, were examined from each village (
n = 288). Genotyping was performed by a nested PCR method using primers specific for allele families of genes for the merozoite surface protein 1 (
msp-1) and merozoite surface protein 2 (
msp-2). A high degree of genetic diversity was found within each village but there were no differences found among the 6 villages. Poisson regressions showed significant effects of host age, village and interaction between host age and village on the complexity of infection. There was a positive, non-linear relationship between complexity of infection and transmission intensity with a maximal number of genotypes found per individual even at high transmission intensities. Furthermore there was a significantly lower complexity found in adults (>15 years) as compared to children (<15 years) in the lowland village. This difference was not found as transmission intensity decreased. By comparing data from the same geographical area, using the same methods, and taking into account confounding factors, the present study provides evidence for an effect of both age and transmission intensity on complexity of infection with
P. falciparum.