Authors

S R Doyle²; S Armoo²; A Renz⁴; M J Taylor³; M Y Osei-Atweneboana¹; W N Grant²;  ¹ Council for Scientific and industrial Research - Water Research Institute, Accra, Ghana;  ² Department of Animal, Plant and Soil Sciences, La Trobe University, Bundoora, 3086, Australia;  ³ Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom;  ⁴ Institute of Evolution and Ecology, Department of Comparative Zoology, University of Tübingen, Germany

Discussion

Transmission of the human filarial nematode Onchocerca volvulus is typically monitored using molecular pool screening techniques and dissection of the Simulid blackly vector. Black flies from disease endemic regions also co-transmit a range of other Onchocerca spp, which can be difficult to distinguish form the human parasite based on morphological characters alone. Here we describe a versatile molecular approach that exploits mitochondrial DNA sequence variation to discriminate between O. volvulus and O. ochengi dissected from black flies. We validated these tools on 185 Onchocerca larvae dissected from black flies captured from 14 communities in Ghana throughout 2011-13, which revealed (i) a higher than expected prevalence of O. ochengi, (ii) evidence for differential migration of both species within different tissues of the fly, and (iii) a non-uniform distribution of the two parasites, with 25%, 47%, and 93% of O. volvulus being found in the western-most (Black Volta, Tain and Tombe), the central Pru and eastern-most Daka river basins, respectively. The tools presented provide a simple and cost-effective approaches to determine the identity and distribution of two Onchocerca species, and will be valuable for future genetic studies that focus on parasites collected from blackflies. The results emphasise the need for molecular identification of parasites collected from blackflies, particularly if inferences regarding transmission of the disease-causing O. volvulus are made.