Abstract：
The seal heartworm Acanthocheilonema spirocauda (Nematoda: Onchocercidae) parasitizes the heart and pulmonary arteries of various phocid seals of the Northern Hemisphere. Over many decades, potential vectors of this parasite have been discussed, and to this date, the life cycle is not fully known. The seal louse Echinophthirius horridus (Anoplura: Echinophthiriidae) is an obligatory, permanent and haematophagous ectoparasite of phocids that has been hypothesized to function as obligate intermediate host for A. spirocauda. We examined 11 adult E. horridus specimens collected from stranded harbour seals (Phoca vitulina) in rehabilitation at the Sealcentre Pieterburen by X-ray microCT imaging, aiming to illustrate larval A. spirocauda infection sites in situ. In three of these specimens, thread-like larvae were detected in insect organs. Detailed imaging of the most infected louse revealed a total of 54 A. spirocauda larvae located either in fat bodies or the haemocoel. Histological analysis of the same specimen illustrated nematode cross-sections, confirming X-ray microCT data. The current data strongly suggest that E. horridus is a natural intermediate host for A. spirocauda. Moreover, we demonstrate the potential of X-ray microCT-based imaging as a non-destructive method to analyze host-parasite interactions, especially in the neglected field of marine mammal parasitology.
摘要：
海豹心虫Acanthocheilonemaspirocauda（Nematoda：Onchocercidae）寄生了北半球各种台风海豹的心脏和肺动脉。几十年来，这种寄生虫的潜在载体已经被讨论过，直到今天,生命周期还不完全清楚。海豹虱Echinophthiriushordus（Anopura：Echinophthiriidae）是强制性的，被认为是A.spirrocauda的专性中间宿主的永久性和嗜血体外寄生虫。我们通过X射线显微CT成像检查了从密封中心Pieterburen的搁浅海豹（Phocavitulina）康复中收集的11个成年E.hordus标本，旨在说明幼虫A.spirocauda感染部位的原位。在其中三个标本中，在昆虫器官中检测到线状幼虫。感染最严重的虱子的详细成像显示，总共有54只螺旋体幼虫位于脂肪体或血液中。相同标本的组织学分析说明线虫的横截面，确认X射线显微CT数据。目前的数据强烈地表明,E.horidus是A.spirocauda的天然中间宿主。此外，我们证明了X射线显微CT成像作为一种非破坏性的方法来分析宿主-寄生虫的相互作用的潜力，尤其是在被忽视的海洋哺乳动物寄生虫学领域。
