Genetic diversity of the Plasmodium falciparum msp2 gene in children from the Eastern Democratic Republic of Congo: a comparative study of clinical and subclinical infections

Plasmodium falciparum is the main cause of malaria-related illness and death in sub-Saharan Africa. Despite control efforts, asymptomatic carriers, particularly children, continue to sustain transmission. Improving surveillance requires a better understanding of the genetic diversity and parasite burden of symptomatic versus asymptomatic infections.

To compare Plasmodium falciparum genotypic profiles and msp2 gene copy numbers in symptomatic and asymptomatic children in Kindu, and assess associations with clinical status.

Children aged 6 months to 12 years were recruited from health centres and schools. DNA extracted from dried blood spots (Chelex^® 100) was analysed by nested PCR to identify msp2 allelic families (FC27, 3D7, multiplicity of infection) and by quantitative PCR to estimate copy number. Statistical tests compared groups and predictors of symptomatic infection.

Of the 522 children included, those in the symptomatic group were younger than those in the asymptomatic group (mean age: 5.77 vs. 7.25 years; p < 0.001) and were more frequently male (70%). P. falciparum prevalence was higher among symptomatic children (69.8%). The FC27 allele family and polyclonal infections (higher multiplicity of infection) were strongly associated with symptomatic malaria (aOR = 6.50 and 24.58, respectively; p < 0.01). Gene copy number was higher in symptomatic and polyclonal infections, but was not independently associated with clinical status after multivariable adjustment (aOR = 0.98; p = 0.134). Parasite positivity remained a strong independent predictor of symptomatic disease (aOR = 3.83; p < 0.001).

Symptomatic malaria in children is more closely associated with parasite genotype diversity than density. This emphasises the importance of control strategies for molecular surveillance.