European Pine Marten (Martes martes) as Natural Definitive Host of Sarcocystis Species in Latvia: Microscopic and Molecular Analysis

Apicomplexan parasites of the genus <i>Sarcocystis</i> utilize a wide range of vertebrate hosts, including reptiles, birds, and mammals, and follow a complex two-host prey-predator life cycle. Sarcocysts develop within the muscle tissue of intermediate hosts, while oocyst sporulation occurs in the intestines of definitive hosts. Despite their broad host range, the role of Mustelidae predators in the transmission and maintenance of <i>Sarcocystis</i> species remains poorly understood, highlighting the need for targeted studies in this area. In 2023, 20 intestinal samples were collected from European pine martens (<i>Martes martes</i>) in Latvia. Light microscopy revealed sporocysts of <i>Sarcocystis</i> spp. in 70.0% of the samples. <i>Sarcocystis</i> species were identified by using the analysis of obtained <i>cox1</i> and <i>ITS1</i> sequences. Using molecular methods, <i>Sarcocystis</i> spp. were confirmed in 85.0% of the samples examined, and co-infections with two or more different parasite species were established in 30.0% samples. We detected eight <i>Sarcocystis</i> species (<i>S</i>. <i>arieticanis</i>, <i>S</i>. <i>bertrami</i>, <i>S. capracanis</i>, <i>S</i>. <i>cruzi</i>, <i>S</i>. <i>entzerothi</i>, <i>S</i>. <i>hjorti</i>, <i>S</i>. <i>morae</i>, and <i>S</i>. <i>truncata</i>) associated with intermediate hosts such as cervids, cattle, sheep, goats, and horses. Additionally, a genetically novel species, <i>Sarcocystis</i> sp. 25MmLV, was detected in a single European pine marten. These findings suggest that European pine martens serve as definitive hosts for multiple <i>Sarcocystis</i> species, particularly those infecting cervids.