Browsing by Author "Chege, William"

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    Genetic diversity and population structure of Plasmodium falciparum in Kenyan–Ugandan border areas
    (wiley publishers, 2019) Nderu, David; Kimani, Francis; Karanja, Evaline; Thiong'o, Kelvin; Akinyi, Maureen; Too, Edwin; Chege, William; Nambati, Eva; Wangai, Laura N.; Meyer, Christian G.; Velavan, Thirumalaisamy P.
    Kenya has, in the last decade, made tremendous progress in the fight against malaria. Nevertheless, continued surveillance of the genetic diversity and population structure of Plasmodium falciparum is required to refine malaria control and to adapt and improve elimination strategies. Twelve neutral microsatellite loci were genotyped in 201 P. falciparum isolates obtained from the Kenyan–Ugandan border (Busia) and from two inland malaria-endemic sites situated in western (Nyando) and coastal (Msambweni) Kenya. Analyses were done to assess the genetic diversity (allelic richness and expected heterozygosity, [He]), multilocus linkage disequilibrium () and population structure. A similarly high degree of genetic diversity was observed among the three parasite populations surveyed (mean He = 0.76; P > 0.05). Except in Msambweni, random association of microsatellite loci was observed, indicating high parasite out-breeding. Low to moderate genetic structure (FST = 0.022–0.076; P < 0.0001) was observed with only 5% variance in allele frequencies observed among the populations. This study shows that the genetic diversity of P. falciparum populations at the Kenyan–Ugandan border is comparable to the parasite populations from inland Kenya. In addition, high genetic diversity, panmixia and weak population structure in this study highlight the fitness of Kenyan P. falciparum populations to successfully withstand malaria control interventions.
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    Plasmodium falciparum histidine-rich protein (PfHRP2 and 3) diversity in Western and Coastal Kenya
    (Nature Publishing Group, 2019-02-08) Nderu, David; Kimani, Francis; Thiong’o, Kelvin; Karanja, Evaline; Akinyi, Maureen; Too, Edwin; Chege, William; Nambati, Eva; Meyer, Christian G.; Velavan, Thirumalaisamy P.
    Plasmodium falciparum histidine-rich proteins 2 (PfHRP2) based RDTs are advocated in falciparum malaria-endemic regions, particularly when quality microscopy is not available. However, diversity and any deletion in the pfhrp2 and pfhrp3 genes can affect the performance of PfHRP2-based RDTs. A total of 400 samples collected from uncomplicated malaria cases from Kenya were investigated for the amino acid repeat profiles in exon 2 of pfhrp2 and pfhrp3 genes. In addition, PfHRP2 levels were measured in 96 individuals with uncomplicated malaria. We observed a unique distribution pattern of amino acid repeats both in the PfHRP2 and PfHRP3. 228 PfHRP2 and 124 PfHRP3 different amino acid sequences were identified. Of this, 214 (94%) PfHRP2 and 81 (65%) PfHRP3 amino acid sequences occurred only once. Thirty-nine new PfHRP2 and 20 new PfHRP3 amino acid repeat types were identified. PfHRP2 levels were not correlated with parasitemia or the number of PfHRP2 repeat types. This study shows the variability of PfHRP2, PfHRP3 and PfHRP2 concentration among uncomplicated malaria cases. These findings will be useful to understand the performance of PfHRP2-based RDTs in Kenya.