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

Apicomplexan parasites of the genus 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 species remains poorly understood, highlighting the need for targeted studies in this area. In 2023, 20 intestinal samples were collected from European pine martens () in Latvia. Light microscopy revealed sporocysts of spp. in 70.0% of the samples. species were identified by using the analysis of obtained and sequences. Using molecular methods, 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 species (. , . , , . , . , . , . , and . ) associated with intermediate hosts such as cervids, cattle, sheep, goats, and horses. Additionally, a genetically novel species, sp. 25MmLV, was detected in a single European pine marten. These findings suggest that European pine martens serve as definitive hosts for multiple species, particularly those infecting cervids.