Institute of Life Sciences and Technology, Daugavpils University, Parādes street 1A, Daugavpils, LV-5401, Latvia.
Laboratory of Molecular Ecology, Nature Research Centre, Akademijos 2, LT-08412, Vilnius, Lithuania.
Parasit Vectors. 2018 Mar 12;11(1):173. doi: 10.1186/s13071-018-2694-y.
Typically, carnivores serve as definitive hosts for Sarcocystis spp. parasites; currently, their role as intermediate hosts is being elucidated. The present study aimed to identify and molecularly characterize Sarcocystis cysts detected in striated muscle of red foxes from different populations in Latvia, Lithuania and Spain.
Muscle samples from 411 red foxes (Vulpes vulpes) and 269 racoon dogs (Nyctereutes procyonoides) from Latvia, 41 red foxes from Lithuania and 22 red foxes from Spain were examined for the presence of Sarcocystis sarcocysts by light microscopy (LM). Sarcocystis spp. were identified by transmission electron microscopy (TEM) and molecular biology techniques.
Sarcocystis cysts were detected in 11/411 (2.7%) Latvian, 3/41 (7.3%) Lithuanian, and 6/22 (27.3%) Spanish red foxes, however, cysts were not observed in the muscles of racoon dogs. Based on LM, TEM, 18S rDNA, 28S rDNA, ITS1, cox1 and rpoB sequences, Sarcocystis arctica and Sarcocystis lutrae cysts were identified in red fox muscles from Latvia and Lithuania, whereas only S. arctica was detected in Spain. The 18S rDNA, 28S rDNA and ITS1 sequences from the 21 isolates of S. arctica from Latvia, Lithuania and Spain were identical. By contrast, two and four haplotypes were determined based on mtDNA cox1 and apicoplast rpoB sequences, respectively. Polymorphisms were not detected between the two isolates of S. lutrae from Latvia and Lithuania. Based on phylogenetic results, S. arctica and S. lutrae were most closely related to Sarcocystis spp. using predatory mammals as intermediate hosts and to Sarcocystis species with a bird-bird life-cycle.
Based on current knowledge, the red fox and Arctic fox (Vulpes lagopus) could act as intermediate host for the same two Sarcocystis species. Molecular results suggest the existence of two genetic lineages of S. arctica, and such divergence relies on its geographical distribution but not on their intermediate host species.
通常情况下，肉食动物是肌肉内孢子虫的终末宿主；目前，它们作为中间宿主的作用正在被阐明。本研究旨在鉴定并分子特征分析在拉脱维亚、立陶宛和西班牙不同地区的红狐横纹肌中检测到的肌肉内孢子虫。
通过光镜（LM）检查来自拉脱维亚的 411 只红狐（ Vulpes vulpes ）和 269 只浣熊犬（ Nyctereutes procyonoides ）、来自立陶宛的 41 只红狐和来自西班牙的 22 只红狐的肌肉样本中是否存在肌肉内孢子虫。通过透射电子显微镜（TEM）和分子生物学技术鉴定肌肉内孢子虫。
在 11/411（2.7%）只拉脱维亚红狐、3/41（7.3%）只立陶宛红狐和 6/22（27.3%）只西班牙红狐的肌肉中检测到肌肉内孢子虫囊，但在浣熊犬的肌肉中未观察到囊。根据 LM、TEM、18S rDNA、28S rDNA、ITS1、cox1 和 rpoB 序列，鉴定拉脱维亚和立陶宛红狐肌肉中的肌肉内孢子虫为北极肉孢子虫和海狸肉孢子虫，而西班牙仅检测到北极肉孢子虫。来自拉脱维亚、立陶宛和西班牙的 21 株北极肉孢子虫的 18S rDNA、28S rDNA 和 ITS1 序列完全相同。相比之下，基于 mtDNA cox1 和质体 rpoB 序列分别确定了两个和四个单倍型。在拉脱维亚和立陶宛的两个海狸肉孢子虫分离株之间未检测到多态性。基于系统发育结果，北极肉孢子虫和海狸肉孢子虫与以捕食性哺乳动物为中间宿主的肌肉内孢子虫以及具有鸟类-鸟类生命周期的肌肉内孢子虫关系最密切。
根据目前的知识，红狐和北极狐（ Vulpes lagopus ）可能作为中间宿主来携带两种相同的肌肉内孢子虫。分子结果表明，北极肉孢子虫存在两个遗传谱系，这种分化依赖于其地理分布，而不依赖于其中间宿主物种。
