Morphological and Molecular Description of Sarcocystis myodes n. sp. from the Bank Vole (Clethrionomys glareolus) in Lithuania

SIMPLE SUMMARY: Representatives of genus Sarcocystis (Apicomplexa, Sarcocystidae) are parasites of mammals, birds, and reptiles. They are characterized by two-host prey-predator life cycle. Rodents are reservoirs of zoonotic diseases and play a significant role in a spread of pathogens. At present, about 40 Sarcocystis species are known to form sarcocysts in muscles and brain of rodents. Most of Sarcocystis spp. in these hosts have been characterized by morphological methods and life cycle investigations. In the present study a new Sarcocystis species, S. myodes is described in skeletal muscles of the bank voles (Clethrionomys glareolus) from Lithuania using morphological, molecular, and phylogenetic analysis. Based on five genetic loci, S. myodes was most closely related to Sarcocystis spp. using predatory mammals as their definitive hosts. The analysis of previous studies indicates that Sarcocystis spp. diversity in voles is not fully revealed. Furthermore, some Sarcocystis spp. formerly detected in voles are important pathogens. Therefore, further molecular examinations are needed for the revision of Sarcocystis spp. in these hosts. ABSTRACT: Numerous rodent species have been broadly examined for Sarcocystis parasites. Nevertheless, recent investigations on Sarcocystis spp. in voles are lacking. As many as 45 bank voles (Clethrionomys glareolus) captured in several locations in Lithuania were examined in the present study. Based on morphological, genetic, and phylogenetic results, sarcocysts detected in one bank vole were described as Sarcocystis myodes n. sp. Using light microscopy analysis, the observed sarcocysts were ribbon-shaped, 6000–3000 × 70–220 µm in size. Sarcocysts were characterized by a relatively thin (about 1 μm) and apparently smooth cyst wall. The lancet-shaped bradyzoites were 9.6–12.0 × 3.1–4.6 μm in size. By transmission electron microscopy, the sarcocyst wall was up to 1 μm thick, parasitophorous vacuolar membrane had small knob-like blebs. Based on 18S rDNA, 28S rDNA, cox1, rpoB, and ITS1 loci, S. myodes showed highest similarity with S. ratti from the black rat (Rattus rattus). According to phylogenetic placement, S. myodes was most closely related to Sarcocystis spp. that employ predatory mammals as their definitive hosts. Morphologically, sarcocysts of S. myodes have similar features to those of S. cernae, S. dirumpens, and S. montanaensis described in voles, however, they use birds of prey or snakes as their definitive hosts.