Genetic Diversity of Plasmodium falciparum before and after intensive and massive relocation of populations into Yaoundé, Cameroon

Author(s): Akindeh Mbuh Nji, Aristid Herve Ekollo Mbange , Abdel Aziz Selly-Ngaloumo, Peter Thelma Ngwa Niba, Jean Paul Kengne Chedjou, Ngum Lesley Ngum, Tsiambom Monju, Lorraine Matchio Fokou-Kuignou, Olivia Achonduh-Atijegbe, Innocent Mbulli Ali, Cyrille Mbanwi Mbu’u, Calvino Tah Fumbah, Sebastien Kenmoe, Jude Bigoga, Wilfred Fon Mbacham

The introduction of new, genetically diverse and divergent populations of Plasmodium falciparum parasites into a given location, due to population influx, may have serious public health consequences. This study compared the genetic diversity (GD) of P. falciparum amongst Cameroonian populations sampled before (2014) and after (2018) intensive and massive relocations due to civil unrest, from affected regions with different malaria dynamics to the capital city Yaounde. For each time point, a subset of 50 samples was retrieved from a pool of samples collected from participant children aged between 6 months and 18 years and adults attending the hospital for outpatient consultation. To precisely assess the breadth of P. falciparum diversity, genotyping was performed using 2 PCR-based techniques which were further evaluated for their performance: nested-PCR targeting the merozoite surface protein 2 (msp2) gene and Random Amplified Polymorphic DNA (RAPD-PCR). Three of the 6 RAPD primers used (R8, E8, L12) yielded useful polymorphic patterns with higher genotyping rates (91-95%) than nested-PCR (67%). There was a significant difference between the 4 (3RAPD and msp2) primers used (ANOVA; P<0.001). Based on msp2, the Multiplicity of Infection in 2014 was greater than in 2018 (2.28 vs. 1.97). The calculated mean of GD parameters across years and markers showed RAPD-R8 had the highest index of GD (Shannon’s Index, Unbiased Nei-GD) except for the Percentage of Polymorphic Loci. These indices, based on RAPD-R8, confirmed the comparatively higher trend of GD in 2014 compared to 2018, respectively - 0.294 vs 0.246; 0.179 vs 0.156; 88.64 vs 75.0. Clustering analysis was also used as a proxy for population structure, with the msp2-based UPGMA distance-tree depicting intermixed and epidemiologically related clonal populations of 2014 and 2018 across sub-trees. Interestingly, the distance-tree based on RAPD-R8 primer revealed 2 clearly distinct unrelated clusters for 2014 alone, suggesting different genetic backgrounds from the rest of intermixed populations. These observations warrant in-depth investigation into how human migration redistributes malaria diversity and the interest of targeting populations with different genetic background for diagnostic purpose.

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