Diagnostik, Prävalenz und Komplexität der Plasmodieninfektion bei drei Monate alten Kindern aus der Ashanti-Region, Ghana

Abstract

The diversity of Plasmodium falciparum infections based on variable surface antigens plays an important role in the development of children`s immunity in their first months of life in malaria endemic areas. Testing of 1070 three months old children in the hyper-/holoendemic Ashanti region in Ghana over a recruitment period of one year provides an insight into the prevalence of the Plasmodium infections in this age cohort, into complexity, seasonal variation and clinical relevance of Plasmodium infections. Clinical examinations, haemoglobin levels and microscopic diagnostics are completed by moleculargenetic tests: A genus- and species-specific PCR is compared with microscopy. Genotyping of the polymorphic surface proteins MSP-1 and 2 (Merozoite Surface Protein 1 and 2) describes the multiplicity of infection. The prevalence of infection is 13.5% in microscopic testing, 14.5% in PCR diagnostics. Compared with microscopy, PCR shows a sensitivity of 79.9% and a specificity of 96%. The mean number of strains of 3.9 strains per isolate reflects a high complexity of infections. There is a linear correlation between the number of clones and the logarithm of parasite density. In the rainy season, the prevalence of infection is 23%, in the dry season, it is 8.5%. Parasite diversity is significantly less in the rainy season than in the dry season. Mean haemoglobin levels in children with Plasmodium infections are significantly lower than those in healthy children. 30% of the children with a Plasmodium infection show malaria specific symptoms. There is no difference in complexity, whether infected children present clinical symptoms or not. Considering the low prevalence of infections, the observed parasitaemias are probably children`s first Plasmodium falciparum infections. A single mosquito bite could lead to multiple infections with a high antigenic variability.