Sarcocystosis infection is caused by coccidian parasites of the genus Sarcocystis. These globally distributed parasites can infect humans, domestic animals, and wildlife. They exhibit a two-host life cycle, involving both intermediate and definitive hosts, based on a prey–predator relationship. The intermediate hosts develop sarcocysts in their muscles after being infected through contaminated food or water, while definitive hosts develop sporocysts in their intestines, completing the parasite's life cycle. Canids, such as wolves, dogs, foxes, jacals, and raccoon dogs are amongst the main spreaders of Sarcocystis spp. Dogs are integral to both human and animal life, and their interaction with humans is an inseparable part of many cultures. They are not only companions but also carriers of various parasitic infections, including Toxocara canis, Echinococcus granulosus, Sarcocystis, etc. However, limited data exist on the role of dogs in transmitting Sarcocystis parasites, particularly in Europe. This study aimed to examine the prevalence and richness of Sarcocystis species in dog feces in Vilnius, Lithuania.

A total of 25 environmental fecal samples of domestic dogs were collected in Vilnius city. Samples were concentrated using the flotation–sedimentation method. Infective forms of Sarcocystis parasites were not observed under the light microscope. However, molecular analyses using nested PCR and sequencing of the mitochondrial cox1 gene led to the identification of four Sarcocystis species, S. miescheriana, S. arieticanis, S. tenella, and S. hjorti, with pigs, sheep, and deer as their intermediate hosts. The prevalence of Sarcocystis spp. was estimated at 32.0%. This study provides the first molecular insights into the diversity of Sarcocystis species in the feces of domestic dogs in Vilnius. These findings underscore the importance of molecular techniques in identifying and understanding the epidemiology of Sarcocystis and pave the way for future research and control measures in Europe and beyond.