MOLECULAR AND MORPHOLOGICAL DETECTION OF SARCOCYSTIS HALIETI IN MUSCLES OF RAPTORS FROM LITHUANIA

The genus Sarcocystis comprises a diverse group of apicomplexan parasites infecting reptiles, birds, and mammals. These parasites are characterized by the formation of sarcocysts in the muscles of the intermediate host (IH) and the development of sporocysts in the intestines of the definitive host (DH). Raptors have been confirmed to be DH for numerous Sarcocystis species, however, there is a lack of studies on Sarcocystis spp. in the muscles of raptorial birds. In the period of 2014-2024, we analysed muscle samples from 90 raptorial birds belonging to orders Accipitriformes, Falconiformes, and Strigiformes collected in different regions of Lithuania for the presence of Sarcocystis spp. The infection rate of Sarcocystis spp. was established by examining methylene blue-stained muscle samples. Sarcocysts in fresh squashed samples were morphologically characterized under the light microscope (LM). Sarcocystis species identification was performed using the internal transcribed spacer 1 (ITS1) region analysis. By LM, one morphological type of sarcocyst was distinguished. Sarcocysts were detected in 8.9% (8/90) of muscles of Lithuanian raptors examined. In addition, Sarcocystis sp. were found in the leg muscles of five raptors 9.3% (5/54). Sarcocysts were present in 5.7% (3/53) of the neck muscles of three raptors studied. Furthermore, Sarcocystis sp. have been observed in the thoracic muscles of one rough-legged buzzard (Buteo lagopus). No sarcocysts were observed in the hearts of birds examined. Overall, of the 243 muscle samples stained with methylene blue, sarcocysts were found in nine of them (3.7%). Only two sarcocysts were excised from fresh samples. In methylene blue-stained samples, sarcocysts were microscopic, looked like tiny threads, had smooth and thin (about 1 µm) cyst wall, and contained banana-shaped bradyzoites. Representatives of one Sarcocystis species, S. halieti were molecularly identified in seven birds. This is the first study to report five new IHs for S. halieti, common buzzard (Buteo buteo), Eurasian goshawk (Accipiter gentilis), rough-legged buzzard, long-eared owl (Asio otus), and tawny owl (Strix aluco). Further investigations are needed to assess the possible pathogenicity of S. halieti in extra-intestinal organs of raptors. The authors are grateful to Kaunas T. Ivanauskas Zoology Museum for providing bird samples used in the study.