Molecular Characterization and Phylogenetic analysis of Wuchereria bancrofti in human blood samples from Malindi and Tana River Delta, endemic regions in Kenya.

Abstract

IntroductionLymphatic filariasis is a debilitating disease caused by filarial worms; Wuchereria bancrofti, Brugia Malayi and B. Timori. It is earmarked for elimination by the year 2020 through the Global Program for the Elimination of Lymphatic Filariasis (GPELF). In Kenya, mass treatment has been ongoing since the year 2002 though it has not been consistent as recommended by World health organization (WHO). Taking this into account, the emergence of W. bancrofti resistance strains against the current choice of drugs cannot be ruled out. Information on genetic structure and variations is important in assessment of Programs success. Data on genetic characterization of W. bancrofti in Kenya is lacking. This study, therefore reports the first genetic diversity of W. bancrofti in two Kenyan endemic regions.\n\nMethodologyGenomic DNA was extracted from 100 human blood samples obtained from Mpirani district in Malindi and Kipini district in Tana River Delta. They were then amplified by PCR and detected through gel electrophoresis. Seventeen PCR products positive for Wuchereria PCR bancrofti were purified and then DNA quantified for Sanger sequencing. Chromas version 2.6.5 and BioEdit softwares were used for sequence alignment and editing. Fourteen sequences were selected for analysis by MEGA7 and six more related sequences retrieved from the Gene Bank for further analysis with the study sequences. Intrapopulation, interpopulation diversity and pair wise distance were determined and the phylogenetic trees constructed. Tajimas D-test of neutrality was also determined and Statistical evolutionary rate was done using Chi-square (X2) test.\n\nResults and DiscussionThe mean diversity of Malindi and Tana River Delta isolates was 1.42 and the overall mean distance was 0.99. Tajimas (D) test for test of Neutrality was 4.149 and nucleotide diversity({pi}) was 0.603. These results revealed high genetic variations of W. bancrofti in Kenyan endemic regions. This variation could be attributed to prolonged use of the mass drug administration (MDA) and the long period of parasite circulation in these populations.\n\nAuthor SummaryElephantiasis is a disabling disease that causes severe swellings to the affected limbs. It is caused by parasites of Wuchereria bancrofti, Brugia Timori and B. malayi which are transmitted by mosquito vectors. The disease is under the control by the Global Programme to eliminate filariasis and due to the effect of continued treatment through mass drug administration there have been changes in the genetic makeup of the parasite. This may result to resistant strains which may have negative impact on the treatment interventions. We therefore aimed at characterizing the genetic sequences of the Wuchereria bancrofti parasite found in Kenya. Through analyzing parasites obtained in different years after treatment, we were able to track any genetic variations since the start of mass drug administration in Kenya. These variations would be due to the effect of drug pressure, human population movements or mosquito vector movement. This kind of study is important for drug developments and for evaluating the progress of the control programmes.