Epidemiology of multiple Plasmodium falciparum infections - 6. Multiple Plasmodium falciparum infections in Tanzanian infants

Paired blood samples from 99 Tanzanian infants were analysed to examine the infection dynamics of Plasmodium falciparum during the first year of life. Infecting parasites were genotyped by polymerase chain reaction amplificat ion of the polymorphic gene for the merozoite surface protein 2 and subsequ ent analysis according to the resulting restriction fragment length polymor phism pattern. The same samples served as controls in a parallel case-contr ol study for which an additional blood sample was taken from each child dur ing a fever episode. The relationship of the number of concurrent infection s (multiplicity) with age and morbidity was analysed and results were compa red to those of a similar study on older children between 2 and 7 years of age, carried out in the same village at the same time. The mean of 2 infect ing genotypes per positive blood sample from community surveys was low comp ared to that in older children, and there was no significant age-dependency of multiplicity within the first year of life. Multiplicity of infection i n fever cases was also independent of age. In infants, multiplicity was pos itively associated with parasite density and risk of clinical malaria, in c ontrast to the situation in older children (>2 years). The findings help in the understanding of infection dynamics, premunition, and development of s emi-immunity in malaria.