Diversity of nematodes infecting the human-biting black fly species, Simulium nigrogilvum (Diptera: Simuliidae) in central Thailand

Huang, Fan and Srisuka, Wichai and Aupalee, Kittipat and Streit, Adrian and Fukuda, Masako and Pitasawat, Benjawan and Junkum, Anuluck and Saingamsook, Jassada and Somboon, Pradya and Takaoka, Hiroyuki and Saeung, Atiporn (2021) Diversity of nematodes infecting the human-biting black fly species, Simulium nigrogilvum (Diptera: Simuliidae) in central Thailand. Acta Tropica, 224. ISSN 0001-706X, DOI https://doi.org/10.1016/j.actatropica.2021.106140.

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Black flies (Diptera: Simuliidae) are known as vectors of disease agents in humans and livestock, with some species being vectors of Onchocerca volvulus, the filarial nematode that is the causative agent of human onchocerciasis. Nematode infections in adult female black flies have been reported from some areas in northern and western Thailand, but not from other regions of Thailand. In this study, wild-caught adult female black flies from the central region of Thailand were examined for infections with nematodes. Collections of adult females were carried out at Khlong Lan district, Kamphaeng Phet province, central Thailand. A molecular approach, based on the mitochondrial (cox1, 12S rRNA) and nuclear (18S rRNA) genes, was used to identify the species of nematodes recovered from the specimens collected. A total of 911 wild-caught adult black flies were collected. Simulium nigrogilvum was the most abundant species (n = 708), followed by S. doipuiense complex (n = 179), S. chamlongi (n = 11), S. umphangense (n = 10), S. chumpornense (n = 1), S. multistriatum species-group (n = 1), and S. maewongense (n = 1). Nematode infections were detected in nine specimens of S. nigrogilvum, of which two were positive for filarial worms (one worm each, infection rate 0.28%) and seven were positive for non-filarial nematodes (11 worms in total, infection rate 0.99%). The two filarial nematodes (third-stage larvae) were identified molecularly as Onchocerca species type I, while the 11 non-filarial nematodes were classified into ascaridoid (n = 2), tylenchid (n = 6) and mermithid (n = 3) nematodes. The results of this study demonstrated that adult female S. nigrogilvum were parasitized with diverse nematodes (filarial and non-filarial). Detection of the infective larvae of Onchocerca sp. type I in S. nigrogilvum confirms that occurrence of zoonotic onchocerciasis is highly possible in Thailand. Additional in-depth investigation of the morphology, life cycle and host-parasite relationship of nematodes that parasitized this black fly host is still needed.

Item Type: Article
Funders: None
Uncontrolled Keywords: Black fly; Zoonotic onchocerciasis; Onchocerca; Mermithid nematodes
Subjects: Q Science > Q Science (General)
R Medicine > RX Homeopathy > Diseases, treatment, etc
Divisions: Deputy Vice Chancellor (Research & Innovation) Office > Tropical Infectious Diseases Research and Education Centre
Depositing User: Ms Zaharah Ramly
Date Deposited: 09 May 2022 01:25
Last Modified: 09 May 2022 01:25
URI: http://eprints.um.edu.my/id/eprint/34430

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