Black flies are blood-sucking insects of public health importance, and they are effective vectors of pathogens and parasites, such as filarial nematodes of the genus Onchocerca. Our previous surveys have shown that individuals of Simulium turgaicum are annoying pests of humans and livestock in the Aras River Basin of Iran. In the present study, adult black flies of S. turgaicum were trapped from different ecotopes of five villages in Khoda-Afarin County, Iran. By using a sensitive nested PCR assay and targeting the nuclear 18S rDNA-ITS1 marker, filarial infections were found in 38 (1.89%) of 2005 black flies. Homology exploration of 360 bp of the sequences indicated that the filarial worms are members of the family Onchocercidae, with maximum alignment scores of 93–95%. Phylogenetic analysis showed that two Iranian Onchocerca isolates were clustered in the O. fasciata–O. volvulus lineage and were well separated from other filarial nematodes. Both the entomological evidence (empty abdomen of the specimens) and climatologic data (adequate accumulated degree days for development) suggest that the filarial DNA was probably that of infective larvae of vertebrates. This is the first report of an infection by Onchocerca species in S. turgaicum and the first record of onchocercids in black flies in Iran; however, more research is required to demonstrate transmission of these filarial worms by black flies in nature.

黑蝇是对公共卫生具有重要意义的吸血昆虫，它们是病原体和寄生虫（例如盘尾丝虫属丝虫线虫）的有效载体。我们之前的调查显示，在伊朗阿拉斯河流域，蝽（Simulium turgaicum）个体是令人讨厌的人类和牲畜害虫。在本研究中，从伊朗科达-阿法林县五个村庄的不同生态环境中捕获了S. turgaicum成年黑蝇。通过使用灵敏的巢式 PCR 检测并针对核18S rDNA-ITS1标记，在 2005 年的 38 只黑蝇（1.89%）中发现了丝虫感染。对 360 bp 序列的同源性探索表明，丝虫是盘尾丝虫科的成员，最大比对得分为 93-95%。系统发育分析表明，两个伊朗盘尾丝虫分离株聚集在带带盘尾丝虫-盘尾丝虫谱系中，并且与其他丝虫线虫有很好的分离。昆虫学证据（标本的空腹部）和气候学数据（足够的发育累积度日）都表明丝虫 DNA 可能是脊椎动物感染性幼虫的 DNA。这是伊朗首次报告S. turgaicum中盘尾丝虫感染，也是伊朗黑蝇中盘尾丝虫感染的首次记录；然而，需要更多的研究来证明这些丝虫在自然界中是通过黑蝇传播的。