Natural infections with larvae of Onchocerca species type I in the human-biting black fly, Simulium nigrogilvum (Diptera: Simuliidae), in western Thailand

Saeung, Atiporn and Srisuka, Wichai and Aupalee, Kittipat and Fukuda, Masako and Otsuka, Yasushi and Taai, Kritsana and Maleewong, Wanchai and Takaoka, Hiroyuki (2020) Natural infections with larvae of Onchocerca species type I in the human-biting black fly, Simulium nigrogilvum (Diptera: Simuliidae), in western Thailand. Acta Tropica, 204. p. 105344. ISSN 0001-706X

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Official URL: https://doi.org/10.1016/j.actatropica.2020.105344

Abstract

Zoonotic onchocerciasis is a human infection caused by Onchocerca species of animal origins and transmitted by black fly vectors. The reported incidence of this disease has increased throughout the world. This study aims to clarify the vectorial roles of black fly species in zoonotic filarial transmission in Tak province, western Thailand. The integrated approach of morphological and DNA sequence-based analyses was used to identify species of both wild-caught female black flies and infective filarial larvae found in the infected black flies. All of 494 female black flies captured were identified as Simulium nigrogilvum, through scanning electron microscopy (SEM) and DNA sequence analyses based on the cytochrome c oxidase subunit I (COI) and subunit II (COII), and the fast-evolving nuclear elongation complex protein 1 (ECP1) genes. Four females of S. nigrogilvum harbored one to three third-stage larvae (infective larvae) in their thoraces, with an infection rate of 0.81% (4/494). All infective larvae were similar in morphology and size to one another, being identified as Onchocerca species type I (= O. sp. type A), a bovine filaria, originally reported from Japan, and also as O. sp. found in S. nodosum in Thailand, based on their body lengths and widths being 1,068–1,346 µm long by 25–28 µm wide, and morphological characters. Comparisons of cytochrome c oxidase subunit I (COI) and 12S rRNA sequences of mitochondrial DNA (mtDNA) and phylogenetic analyses with those of previous reports strongly supported that all larvae were O. sp. type I. This report is the first indicating the presence of O. sp. type I in Thailand and its vector being S. nigrogilvum. © 2020 Elsevier B.V.

Item Type: Article
Uncontrolled Keywords: Filaria; Zoonotic onchocerciasis; COI; COII; ECP1
Subjects: R Medicine
Divisions: Deputy Vice Chancellor (Research & Innovation) Office > Tropical Infectious Diseases Research and Education Centre
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 28 Jul 2020 02:59
Last Modified: 28 Jul 2020 02:59
URI: http://eprints.um.edu.my/id/eprint/25201

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