Molecular Identification of Onchocerca Species among Residents of Benue and Cross River States, Nigeria, Using Known Microsatellites and Mitochondrial DNA

Abstract

Background: Human onchocerciasis is a neglected tropical disease caused by Onchocerca volvulus and is transmitted by the species Simulium damnosum. Currently, onchocerciasis is estimated to have infected over 37million people in tropical Africa, Yemen and Latin America, resulting in a debilitating eye and skin disease in more than 5million people with over 1.2 million cases of visual impairment or blindness. Also, an estimate of about 120 million people is at risk of contracting the disease due to the breeding habit of the vector. Community-directed ivermectin administration has greatly reduced the infection burden in different parts of the world but they are persistent cases of onchocerciasis infection in Benue and Cross River States, Nigeria due to the terrain, relapse/poor ivermectin coverage, and COVID-19 outbreak. Aims and Objectives: To investigate the prevalence of onchocerciasis in these localities, this study reported the use of mitochondrial DNA and microsatellite markers for molecular identification studies of Onchocerca species amongst residents of Benue and Cross River State, Nigeria. Materials and Method: Three hundred (300) patients from Benue and Cross River State, Nigeria, 150 patients each from both states were screened using SD Bioline onchocerciasis test strip from South Korea with batch no: 61ADE002B for the detection of IgG4 antibodies against Ov16 in onchocerciasis. 25 were positive from Cross River State and 20 from Benue state. Six (6) from each state were sent for DNA extraction and PCR amplification (L1-6=Benue State, L6-12= Cross River) using polymerase chain reaction (PCR) amplification of mitochondrial cytochrome C oxidase subunit I (COXI) genes using HC02198: 5’-TAAACTTCAGGGTGACCAAAAAATCA-3’ primers and the primers of the respective microsatellites; (GT)AT(GT)AT(GT)10, (GT)GC(GT)10, (CAG)₂(CAA)₁₀(CAG), and (GT)11TT(GT). Results: The results showed amplification of COX 1 subunit of the mtDNA of Onchocerca volvulus at 344bp DNA sequence and amplification of (GT)AT(GT)AT(GT)10 microsatellites at 193bp, (GT)GC(GT)10 at 180bp, (CAG)₂(CAA)₁₀(CAG) at 209bp, and (GT)11TT(GT) 195bp respectively. Conclusion: This study clearly showed that active transmission of human onchocerciasis infection is still ongoing in Wanikade and Igede communities of Benue and Cross River State as evident by the skin lesions and depigmentation presented by a 55 years old woman and the molecular parasitological evidence of the incidence Onchocerca volvulus using the parasites’ genetic materials. Therefore, we recommend intensifying community-directed ivermectin
intervention in these states.