Morphometric and DNA investigation results of Sarcocystis wobeseri sp. nov. from the barnacle goose (Branta leucopsis) and Sarcocystis sp. (cyst type IV) from the mallard duck (Anas platyrhynchos) are presented. No significant morphometric differences between the investigated Sarcocystis species were found. ITS-1, 18S rRNA, and 28S rRNA gene sequences of these species showed 100% identity. The conclusion is drawn that it is one and the same Sarcocystis species in different intermediate hosts.

Macroscopic Sarcocystis cysts were detected in the muscles of 28 Mallards ( Anas platyrhynchos ), 1 Eurasian Wigeon ( Anas penelope ), and 1 Common Teal ( Anas crecca ) hunted in Lithuania and Finland. According to the sequences of the 18S rRNA gene, 28S rRNA gene, and ITS-1 region, the macrocysts examined from all 30 ducks belonged to Sarcocystis rileyi. This parasite was found in the Eurasian Wigeon and the Common Teal for the first time. All S. rileyi isolates examined were identical to each other and differed from 2 S. rileyi isolates previously reported from 2 Mallards from the United States only by 1 nucleotide substitution within the ITS-1 region.

On the basis of the already published morphological, 18S rDNA, 28S rDNA data (Kutkienė et al., Parasitol Res 99:562-565, 2006; Parasitol Res 102:691-696, 2008; Parasitol Res 104:329-336, 2009), and ITS-1 region investigation results of sarcocysts presented in this paper, Sarcocystis albifronsi sp. nov. from the white-fronted goose (Anser albifrons) and Sarcocystis anasi sp. nov. from the mallard duck (Anas platyrhynchos) are described.

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.

Background: Birds of the family Laridae have not been intensively examined for infections with Sarcocystis spp. To date, sarcocysts of two species, S. lari and S. wobeseri, have been identified in the muscles of gulls. The aim of the present study was to evaluate the species richness of Sarcocystis in the herring gull, Larus argentatus, from Lithuania. Methods: In the period between 2013 and 2019, leg muscles of 35 herring gulls were examined for sarcocysts of Sarcocystis spp. Sarcocystis spp. were characterised morphologically based on a light microscopy study. Four sarcocysts isolated from the muscles of each infected bird were subjected to further molecular examination. Sarcocystis species were identified by means of ITS1 sequence analysis. Results: Sarcocysts were detected in 9/35 herring gulls (25.7%). Using light microscopy, one morphological type of sarcocysts was observed. Sarcocysts were microscopic, thread-like, had a smooth and thin (about 1 µm) cyst wall and were filled with banana-shaped bradyzoites. On the basis of ITS1 sequences, four Sarcocystis species, S. columbae, S. halieti, S. lari and S. wobeseri, were identified. Furthermore, it was demonstrated that a single infected herring gull could host two Sarcocystis species indistinguishable under light microscopy. Conclusions: Larus argentatus is the first bird species found to act as intermediate host of four Sarcocystis spp. According to current knowledge, five species, S. falcatula, S. calchasi, S. wobeseri, S. columbae and S. halieti can use birds belonging to different orders as intermediate hosts.