Wyoming State Veterinary Laboratory, Department of Veterinary Sciences, University of Wyoming,1174 Snowy Range Road, Laramie, Wyoming 82070, USA.
Wyoming Game and Fish Department, 1212 S Adams Street, Laramie, Wyoming 82070, USA.
J Wildl Dis. 2021 Jan 6;57(1):71-81. doi: 10.7589/JWD-D-20-00023.
Dictyocaulus spp. infections are common in North American cervids, with Dictyocaulus viviparus described as most common. A Rocky Mountain elk (Cervus canadensis nelsoni) was found dead in Wyoming, US with significant bronchitis and pneumonia. In the bronchi and trachea, numerous large nematodes were found and grossly identified as Dictyocaulus spp. lungworms. Macroscopic alterations, such as distended interlobular septa and edema with foam and mucus observed on cut surface and in trachea and bronchi, were consistent with those commonly described in D. viviparus infections. Female lungworms were identified to Dictyocaulus spp. level via morphologic examination and molecular analyses based on mitochondrial cyclooxygenase 1 and 18S ribosomal RNA genes. A phylogenetic analysis was conducted employing the maximum likelihood method. Based on both morphologic and genetic assays, the isolated lungworms were most likely a strain of Dictyocaulus cervi. Within the female adult worms, free first stage larvae were observed besides worm eggs, which had not been described for Dictyocaulus spp. Phylogenetic analysis revealed that our parasites clustered closely with D. cervi, forming a subclade with that species within a larger clade that includes Dictyocaulus eckerti. While the elk tested positive for chronic wasting disease, it is assumed that significant pathology in the present case was caused directly by infection with the D. cervi-like lungworm, not previously described in North America.
双腔吸虫属感染在北美有蹄类动物中很常见，其中 viviparus 型最为常见。在美国怀俄明州，一只落基山麋鹿（Cervus canadensis nelsoni）被发现死亡，患有明显的支气管炎和肺炎。在支气管和气管中，发现了许多大型线虫，并大体上鉴定为双腔吸虫属肺线虫。肉眼观察到的间质性隔膨胀和水肿伴有泡沫和黏液等宏观改变与 viviparus 型感染中常见的改变一致。通过形态学检查和基于线粒体环氧化酶 1 和 18S 核糖体 RNA 基因的分子分析，将雌性肺线虫鉴定为双腔吸虫属水平。采用最大似然法进行了系统发育分析。基于形态学和遗传学检测，分离出的肺线虫最有可能是鹿双腔吸虫的一个株系。在雌性成虫中，除了虫卵外，还观察到自由的第一期幼虫，这在双腔吸虫属中尚未描述过。系统发育分析表明，我们的寄生虫与鹿双腔吸虫密切聚类，在包括狄氏双腔吸虫在内的更大聚类中与该物种形成一个亚群。虽然麋鹿检测出慢性消耗病呈阳性，但假设在本病例中，显著的病理学是由以前在北美的狄氏双腔吸虫样肺线虫感染直接引起的，而不是由慢性消耗病引起的。
