Evolutionary relationships and secondary structural analysis of the human filarial parasite Onchocerca volvulus based on 28S rRNA Sequences

Onchocerca volvulus is the causative agent of onchocerciasis (river blindness), transmitted between hosts by blackflies of the genus Simulium. This debilitating disease poses a significant public health challenge, causing both cutaneous and ocular manifestations. This study aimed to compare the partial 28S ribosomal RNA (rRNA) sequence of O. volvulus to determine its secondary structure and molecular phylogeny. Using PCR, an 861-bp genomic DNA fragment from O. volvulus, designated as Ov28SrRNA was successfully amplified and sequenced. The PCR products were fractionated on an agarose gel and subsequently sequenced; yielding a fragment of 861 bp. Taxonomic analysis identified 96 sequence matches within the superfamily Filarioidea, with 93 hits associated with the family Onchocercidae. A comparative search using the Rfam database revealed high similarity to known eukaryotic large subunit rRNA sequences (RF02543), corresponding to one hit for O. volvulus. Multiple sequence alignment of O. volvulus with 11 Onchocerca species revealed a sequence similarity range of 85.73%-92.45%. The RNAfold algorithm predicted an optimal secondary structure with a minimum free energy of -258.31 kcal/mol and an ensemble diversity of 140.91, indicating considerable structural variability. Phylogenetic analysis revealed that O. volvulus formed a sub-cluster with O. lienalis and O. ochengi and O. lupi. The lowest genetic distance (0.8%) was observed between O. volvulus and the two bovine filarial parasites O. lienalis and O. ochengi, as well as O. lupi, a parasite of carnivores. Understanding the evolutionary relationships of O. volvulus may provide valuable insights into the bovine parasite-host model, which could be utilized for screening chemical compounds with potential applications against the human parasite.