High prevalence of Sarcocystis spp. in the Eurasian wolf (Canis lupus lupus)

Sarcocystis spp. are obligate heteroxenous protozoa. Transmission follows a predator-prey cycle involving an intermediate host (IH) and a definitive host (DH). DHs can be infected with multiple Sarcocystis spp. at the same time, which complicates species identification. We aimed to determine the prevalence and species diversity in free-ranging wolves in Switzerland. A further goal was to evaluate the utility of Next-generation sequencing (NGS) for resolving mixed infections. A total of 87 wolf intestinal content samples were collected between 2017-2023 and analyzed coproscopically. Oocysts/sporocysts were detected in 76%. DNA was obtained from 57/66 positive samples and 55/57 resulted positive in a Sarcocystis 18S rRNA PCR. Additionally, mitochondrial cytochrome c oxidase subunit I (COI) gene PCR and a real-time PCR targeting S. cruzi were performed. PCR products from conventional PCRs were submitted for Sanger sequencing. Monoinfections were identified in 16% and mixed infections in 84%. A subset of five samples was analyzed by NGS of the 18S rRNA fulllength and COI fragment PCR products. Molecular analysis identified nine different Sarcocystis species. Newly developed pipelines provided high-resolution species-level identification in mixed infections. These findings confirm the Eurasian wolf as DH for multiple Sarcocystis species for the first time.

2025

dissertation

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