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Discrimination between Onchocerca volvulus and O. ochengi filarial larvae in Simulium damnosum (s.l.) and their distribution throughout central Ghana using a versatile high-resolution speciation assay

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Doyle, Stephen R, Armoo, Samuel, Renz, Alfons, Taylor, Mark, Osei-Atweneboana, Mike Yaw and Grant, Warwick N (2016) 'Discrimination between Onchocerca volvulus and O. ochengi filarial larvae in Simulium damnosum (s.l.) and their distribution throughout central Ghana using a versatile high-resolution speciation assay'. Parasites & Vectors, Vol 9, p. 536.

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Abstract

BACKGROUND
Genetic surveillance of the human filarial parasite, Onchocerca volvulus, from onchocerciasis endemic regions will ideally focus on genotyping individual infective larval stages collected from their intermediate host, Simuliid blackflies. However, blackflies also transmit other Onchocerca species, including the cattle parasite O. ochengi, which are difficult to distinguish from the human parasite based on morphological characteristics alone. This study describes a versatile approach to discriminate between O. volvulus and O. ochengi that is demonstrated using parasite infective larvae dissected from blackflies.

RESULTS
A speciation assay was designed based on genetic differentiation between O. volvulus and O. ochengi mitochondrial genome sequences that can be performed in high-throughput high-resolution melt (HRM)- or lower throughput conventional restriction fragment length polymorphism (RFLP) analyses. This assay was validated on 185 Onchocerca larvae dissected from blackflies captured from 14 communities in Ghana throughout 2011-2013. The frequency of O. ochengi was approximately 67 % of all larvae analysed, which is significantly higher than previously reported in this region. Furthermore, the species distribution was not uniform throughout the study region, 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.

CONCLUSIONS
This tool provides a simple and cost-effective approach 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 presented highlight the need to discriminate Onchocerca species in transmission studies, as the frequency of each species varied significantly between the communities studied.

Item Type: Article
Subjects: QX Parasitology > Helminths. Annelida > QX 301 Filarioidea
QX Parasitology > Insects. Other Parasites > QX 505 Diptera
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 880 Filariasis and related conditions (General)
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 885 Onchocerciasis
Faculty: Department: Biological Sciences > Department of Tropical Disease Biology
Digital Object Identifer (DOI): https://doi.org/10.1186/s13071-016-1832-7
Depositing User: Jessica Jones
Date Deposited: 18 Oct 2016 13:40
Last Modified: 06 Feb 2018 13:13
URI: https://archive.lstmed.ac.uk/id/eprint/6279

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