Molecular Characterization of Onchocerca volvulus Infected Simulium damnosum and the Physicochemical Parameters Supporting the Fly Distribution along the Gamji Park Section of River Kaduna

Abstract

The blackfly (Simulium damnosum) found along fast flowing streams and river is the primary vector of Onchocerca volvulus, parasite in most parts of Africa including Nigeria that leads to irreversible blindness. This study aimed to evaluate the distribution and physicochemical parameters supporting Onchocerca volvulus infected blackflies along the Gamji Park section of River Kaduna and their molecular characterization using 0-150 OV and 12S rRNA. A grand total of 2689 blackflies were collected from the study site using hand scooping net and preserved in 80% ethanol for entomological studies. Out of these, 300 flies were randomly selected and divided into pools of 50 flies for DNA extraction and amplification. Purified DNA obtained was subjected to PCR analysis and amplified using the primers 12SrRNA for Simulium species and the 0-150OV for Onchocerca volvulus. The physicochemical parameters of the sampling station were also determined and correlated with number of flies caught. A non-significant negative correlation was observed between the dissolved oxygen, total dissolved solids, conductivity, velocity and number of blackflies caught during the dry (November to April) and rainy (May to October) seasons. Gene amplification generated a band size of 196bp for Simulium species and 190bp for Onchocerca volvulus. Sequencing and BLAST of the PCR products using the 12SrRNA confirmed different identities of nine strains of Simulium damnosum species. In conclusion, the results suggested abundance of blackflies many of which were infected with Onchocerca volvulus in the area; indicating a silent and moderate transmission of Onchocerca volvulus going on along the river.