Molecular Evidence of Raccoon Dog (Nyctereutes procyonoides) as a Natural Definitive Host for Several Sarcocystis Species

<i>Sarcocystis</i> parasites infect a wide range of animals, including reptiles, birds, and mammals, and have complex two-host prey-predator life cycle. Sarcocysts are mainly found in the muscles of intermediate hosts, and oocysts sporulate in the intestines of the definitive host. The raccoon dog (<i>Nyctereutes procyonoides</i>), native to Asia and invasive in Europe, is a known disease carrier. However, studies on raccoon dogs in the transmission of <i>Sarcocystis</i> are scarce. Between 2019 and 2024, a total of 26 raccoon dog carcasses were collected in Lithuania. The results of a light microscopy examination indicated that 50% of the samples were positive for <i>Sarcocystis</i> spp. sporocysts and sporulated oocysts. Based on nested PCR and sequencing of <i>cox1</i>, 88.5% of the samples were positive for these parasites. Molecular analysis revealed the presence of 11 different <i>Sarcocystis</i> species. Eight species, including <i>S. alces</i>, <i>S. capracanis</i>, <i>S. hjorti</i>, <i>S. iberica</i>, <i>S. linearis</i>, <i>S. morae</i>, <i>S. tenella</i>, and <i>S. venatoria</i> were reported for the first time in raccoon dogs as definitive hosts. The identified <i>Sarcocystis</i> species were linked to intermediate hosts, such as cervids, wild boars, pigs, goats, and sheep. These findings suggest that raccoon dogs play a key role in the spread of <i>Sarcocystis</i>, particularly species infecting cervids.