MOLECULAR CHARACTERIZATION OF SIMULIUM DAMNOSUM COMPLEX IN AN ENDEMIC FOCUS OF GURARA RIVER, KAGARKO LGA, KADUNA STATE, NIGERIA
MOLECULAR CHARACTERIZATION OF SIMULIUM DAMNOSUM COMPLEX IN AN ENDEMIC FOCUS OF GURARA RIVER, KAGARKO LGA, KADUNA STATE, NIGERIA
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Date
2018-08
Authors
OLUWASEGUN, Ashade Noah
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Abstract
The black flies (Diptera: Simuliidae), vectors of onchocerciasis are difficult to be distinguished morphologically. This study was carried out to characterize the residing Simulium damnosum complex collected along Gurara River focus, Kagarko LGA of Kaduna State, Nigeria. Morphological identity was determined using WHO/OCP colour classification criteria and transmission potential of the obtained adult female S. damnosum complex was done under stereo microscope as the first approach. Similarly, genomic DNA extractions and PCR were used to identify S. damnosum complex collected from morphologically verified populations based on ITS, ITS1, and ITS2 of nuclear ribosomal gene (NRG); and 16S rRNA of mitochondrial ribosomal gene (MRG). In addition, bioinformatics involving the use of BLAST and molecular evolutionary genetics analysis version six software (MEGA 6.06) were applied in the characterization. Results of morphological identification reflected the black flies to be S. damnosum sub-complex (i. e., savanna group) with zero transmission potential as the monthly transmission potential (MTP) was calculated to be zero. Whereas the PCR mediated assays yielded different amplicon sizes on agarose gel electrophoresis. The result of the ITS amplifications warrants further comments for heterozygous alleles – indicated by electrophoregram amplicon 2A and 2B of ITS/NRG. Also, the BLASTN results of ITS/NRG amplicon 2A and 3 nucleotide sequence suggested they might be new cryptic species as they did not have any corresponding sequences from the NCBI GenBank database. Meanwhile, the phylogenetic and molecular evolutionary analyses gave topology of trees that are quite similar for ITS, ITS1 and ITS2 of NRG, except that the tree topology for 16S rRNA of MRG are different from others. The different PCR amplicon sizes examined from the results was used to bypass the cytological examination of larvae for identification. However, S. damnosum clones (suspected to be S. damnosum sensu stricto), S. sirbanum (both savanna group); and S. sanctipauli (a forest group) were revealed as closely related sister members for ITS, ITS1 and ITS2 phylogenies. These results can also facilitate the understanding of the species groups of the black flies available at the study focus. At molecular level, the ITS marker was of the most identification utility among the markers of NRG, while by phylogenetic, the ITS, ITS1 and ITS2 markers gave phylogenies with better identification insight than the 16S rRNA marker from this study.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF SCIENCE IN BIOTECHNOLOGY DEPARTMENT OF BIOCHEMISTRY FACULTY OF LIFE SCIENCES AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
MOLECULAR CHARACTERIZATION,, SIMULIUM DAMNOSUM COMPLEX,, ENDEMIC FOCUS,, GURARA RIVER,, KAGARKO LGA,, KADUNA STATE,, NIGERIA,