Is genetic diversity of Plasmodium falciparum suggestive of malaria endemic zone in West Africa? An attempt to respond by a cross-sectional comparative study between Senegal and Nigeria

Background: Characterization of malaria parasite populations in different endemic settings (from low to high) could be helpful for ascertaining the progress of malaria interventions in endemic settings. The present study aims to compare Plasmodium falciparum parasite population structure between two West African countries with very different level of endemicity using P. falciparum allelic polymorphic markers: msp1 and msp2. Methods: Parasite genomic DNA was extracted from 187 dried blood spot collected from confirmed uncomplicated P. falciparum malaria infected patients in Senegal (94) being at the pre-elimination stage in most part of the country and Nigeria (93) which is still at the control stage. Allelic polymorphism of msp1 and msp2 genes were assessed by nested PCR. Results: In Senegal as well as in Nigeria, K1 and IC3D7 allelic families were the most represented for msp1 and msp2 genes respectively. A higher multiplicity of infection (MOI) was found in both study sites in Senegal (Thies:1.51/2.53; Kedougou:2.2/2.0 for msp 1/2) than from sites in Nigeria (Gbagada: 1.39/1.96; Oredo: 1.35/1.75]). The heterozygosity of msp 1 gene was higher in P. falciparum isolates from Senegal (Thies: 0.62; Kedougou: 0.53) than isolates from Nigeria (Gbagada: 0.55; Oredo: 0.50). In Senegal, K1 alleles were associated with heavy (28) than with moderate (18) infections, in Nigeria however, equal proportions of K1 were observed in both infection types. The IC3D7 subtype allele of the msp 2 family showed high occurrence in heavily infected individuals from both countries (Senegal- 32; Nigeria- 26) than in the moderately infected participants. Conclusion: With the unusual high genetic diversity obtained in low endemic setting in Senegal and low genetic diversity in a high endemic Nigerian setting, multiple holistic approach should be employed in evaluating the actual transmission of a place in order to effectively direct control measures.