Syngamid worms (Nematoda: Syngamidae) parasitizing birds of prey are considered cosmopolitan, but the efforts to understand their biology and systematics are restricted to the Holarctic region. However, in the Neotropical region there is only one recent record with no data about its molecular characterization or its significance to the health of its hosts. Thus, this study aimed to identify through an integrative approach the Syngamid worms parasitizing a native owl, and to describe its pathological consequences. A total of 14 barn owls (Tyto alba) were dissected between 2015 and 2021, from which one bird was found to be parasitized by a high parasitic burden (i.e. 185 worms). Considering light microscopy and SEM, these nematodes were morphologically identified as Cyathostoma americana, and then supported through molecular analyses of nuclear loci ITS and LSU. The pathological changes were described as severe airsacculitis and pneumonia, which probably were the cause of death of the bird. This study represents the first effort to characterize the parasitism by this nematode in a nocturnal bird of prey from the Neotropics, with a lethal outcome. Additional studies are required from other geographical areas and Neotropical countries to better understand the dynamics of this parasite and their hosts, considering both diurnal and nocturnal birds of prey.

寄生于猛禽的合成线虫（线虫纲：合成线虫科）被认为是世界性的，但了解其生物学和系统学的努力仅限于全北区。然而，在新热带地区，只有一项最近的记录，没有关于其分子特征或其对其宿主健康的重要性的数据。因此，本研究旨在通过综合方法识别寄生于本地猫头鹰的 Syngamid 蠕虫，并描述其病理后果。 2015 年至 2021 年间，总共解剖了 14 只仓鸮（ Tyto alba ），其中一只鸟被发现寄生有高寄生负担（即 185 条蠕虫）。考虑到光学显微镜和SEM，这些线虫在形态学上被鉴定为Cyathhostoma americana ，然后通过核位点ITS和LSU的分子分析得到支持。病理变化被描述为严重的气囊炎和肺炎，这可能是该鸟的死亡原因。这项研究是首次尝试描述这种线虫对新热带地区夜间活动的猛禽的寄生特征，并产生致命的结果。需要其他地理区域和新热带国家进行更多研究，以更好地了解这种寄生虫及其宿主的动态，考虑到白天和夜间的猛禽。