Seasonal variation and high multiplicity of first Plasmodium falciparum infections in children from a holoendemic area in Ghana, West Africa.

Objective: To assess the prevalence and multiplicity of Plasmodium falciparum infections in Ghanaian infants.

Method: In an epidemiological study in an area holoendemic for malaria in Ghana, the prevalence and multiplicity of P. falciparum infections (MOI) were assessed in 1069 three month-old infants by typing of the genes encoding the merozoite surface proteins 1 and 2 (msp-1, msp-2) over a recruitment period of one year. Alleles were amplified using allele family-specific polymerase chain reaction (PCR) assays and determined according to their length polymorphisms on a genetic analyzer.

Results: The occurrence of early infections was dependent on the season (month-stratified prevalence 6.4-29.0%). Diversity of msp-alleles was extensive and significantly higher in the dry than in the rainy season.

Conclusions: The level of infection prevalence and the high multiplicity of infections (median 4, maximum 14 strains per isolate) in the first months of life indicate early contacts with parasites exhibiting a wide repertoire of antigens and, most likely, multiple infections per single mosquito bite.