Assessment Of Genetic Diversity, Complexity Of Infection Of Plasmodium Falciparum And Resistance To Antimalarial Drugs In Two Ecological Zones In Ghana

ABSTRACT

Introduction: One major challenge to the global agenda for the elimination of malaria is the extensive genetic diversity of the parasite population, resulting in the development of drug resistance and variation in antigens targeted for vaccine development. The aim of this study was to decipher any ecological difference in the evolution of drug resistance and to determine how much the increased use of artemisinin-based combination therapies (ACTs) and other control interventions are shaping the genetic diversity of the Plasmodium falciparum population in two ecologically distinct populations in Ghana. Methods: A total of 803 dried blood spots (DBS) collected on filter paper from symptomatic children, aged 6 months to 14 years, with P. falciparum mono-infection in the coastal savanna (Cape-Coast) and the forest (Begoro) zones of Ghana from 2014 to 2017. In addition, a total of 991 P. falciparum infected DBS were collected from asymptomatic school children, aged 6 years to 14 years from 2013 to 2017. The study leveraged the high specificity and relatively low-cost of targeted next generation sequencing using molecular inversion probes for targeting and sequencing on the illumina MISEQ platform for sequencing of P. falciparum genes (pfcrt, pfdhfr, pfdhps, pfmdr1 and pfk13) implicated in anti-malarial resistance to chloroquine (CQ), sulfadoxine pyrimethamine (SP), lumefantrine, amodiaquine and artemisinin. The Plasmodium falciparum Apical Membrane Antigen 1 (pfama1) gene was also sequenced for the genetic diversity and complexity of P. falciparum infections (COI) analysis. Genetic diversity was compared between the two study populations and the sequences from Ghana were iii compared with sequences from West Africa, East Africa and South East Asia obtained from the gene bank. Results: The result showed high genetic diversity in pfama1 in Ghanaian sequences with a total of 164 pfama1 haplotypes and a haplotype diversity of 0.993. There was no genetic differentiation between the two study populations in Ghana. Parasite isolates from the two ecological zones in Ghana showed a moderate genetic differentiation with sequences from Thailand (Fst=0.054) and low differentiation with sequences from Kenya (Fst=0.004). Seventy three percent (73%) of the infections were monoclonal. The major molecular marker associated with CQ resistance pfcrt K76T significantly reduced over the four years of the study (χ² = 40.57; p