Analysis of Plasmodium falciparum infections in a village community in Northern Nigeria: determination of msp2 genotypes and parasite-specific IgG responses

The genetic diversity of P. falciparum and multiplicity of infection has be en studied in a village in Northern Nigeria at the end of the rainy season, when transmission is high. We analysed blood samples from 104 individuals aged 5-70 years by polymerase chain reaction (PCR) amplifying the gene for the merozoite surface protein MSP2 followed by genotyping based on restrict ion fragment length polymorphism (RFLP). 94.2% of all samples were parasite positive by PCR and over 80% of those had multiple infections. The age dis tribution of the average number of parasite clones present in P. falciparum infections showed an initial increase, then reached a peak multiplicity in children 8-10 years of age, and afterwards decreased significantly with ag e. Mean multiplicity in those 8-10-year-old children was 5.4 clones per car rier. Peak multiplicity and parasite diversity in Nigerian individuals is c ompared to findings from other study sites in Africa and PNG. The prevalenc e of IgG antibodies against the circumsporozoite protein (CSP), an indicato r for malaria exposure, was over 85% in all age groups showing a high expos ure of villagers to P. falciparum. OD values in ELISA were positively corre lated with age. There was no correlation between the level of IgG against C SP and the multiplicity of P. falciparum infections determined by PCR of ms p2. These results imply that in highly endemic areas multiplicity of infect ion is not directly correlated with exposure to P. falciparum. (C) 2000 Els evier Science B.V. All rights reserved.