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Identification of the onchocerciasis vector in the Kakoi-Koda focus of the Democratic Republic of Congo

Post, RJ, Laudisoit, A, Mandro, M, Lakwo, T, Laemmer, C, Pfarr, K, Hoerauf, A, Tortosa, P, Gomard, Y, Ukety, T, Mande, C, Farovitch, L, Amazigo, U, Bakajika, D, Oguttu, DW, Awaca, N and Colebunders, R (2022) Identification of the onchocerciasis vector in the Kakoi-Koda focus of the Democratic Republic of Congo. PLoS neglected tropical diseases, 16 (11). ISSN 1935-2727

Identification of the onchocerciasis vector in the Kakoi-Koda focus of the Democratic Republic of Congo.pdf - Published Version
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Open Access URL: http://dx.doi.org/10.1371/journal.pntd.0010684 (Published version)


Background: The objective of this study was to characterise the vector in a small hyper-endemic focus of onchocerciasis (the Kakoi-Koda focus) which has recently been discovered on the western slopes of the rift valley above Lake Albert.
Methodology/Principal Findings: Aquatic stages of blackflies were collected by hand from streams and rivers, and anthropophilic adult females were collected by human landing catches. Using a combination of morphotaxonomy and DNA barcoding, the blackflies collected biting humans within the focus were identified as Simulium dentulosum and Simulium vorax, which were also found breeding in local streams and rivers. Simulium damnosum s.l., Simulium neavei and Simulium albivirgulatum were not found (except for a single site in 2009 where crabs were carrying S. neavei). Anthropophilic specimens from the focus were screened for Onchocerca DNA using discriminant qualitative real-time triplex PCR. One specimen of S. vorax was positive for Onchocerca volvulus in the body, and out of 155 S. dentulosum, 30% and 11% were infected and infective (respectively). Conclusions/Significance: Simulium dentulosum currently appears to be the main vector of human onchocerciasis within the Kakoi-Koda focus, and S. vorax may be a secondary vector. It remains possible that S. neavei was the main (or only) vector in the past having now become rare as a result of the removal of tree-cover and land-use changes. Simulium vorax has previously been shown to support the development of O. volvulus in the laboratory, but this is the first time that S. dentulosum has been implicated as a probable vector of onchocerciasis, and this raises the possibility that other blackfly species which are not generally considered to be anthropophilic vectors might become vectors under suitable conditions. Because S. dentulosum is not a vector in endemic areas surrounding the Kakoi-Koda focus, it is probable that the Kakoi-Koda focus is significantly isolated.

Item Type: Article
Uncontrolled Keywords: Animals; Humans; Simuliidae; Onchocerca volvulus; Onchocerciasis; Insect Vectors; Adult; Democratic Republic of the Congo; Female; Plant Breeding; Adult; Animals; Female; Humans; Onchocerciasis; Democratic Republic of the Congo; Insect Vectors; Plant Breeding; Onchocerca volvulus; Simuliidae; 06 Biological Sciences; 11 Medical and Health Sciences; Tropical Medicine
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QH Natural history > QH426 Genetics
R Medicine > R Medicine (General)
R Medicine > RM Therapeutics. Pharmacology
Divisions: Biological & Environmental Sciences (from Sep 19)
Publisher: Public Library of Science (PLoS)
SWORD Depositor: A Symplectic
Date Deposited: 03 Jan 2023 12:29
Last Modified: 03 Jan 2023 12:29
DOI or ID number: 10.1371/journal.pntd.0010684
Editors: Basáñez, María-Gloria
URI: https://researchonline.ljmu.ac.uk/id/eprint/18519
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