Seasonal Dynamics and Potential Interactions of Haematophagous Abomasal Nematodes in two Chamois populations in the Czech Republic

Background: Pathogenic blood-feeding nematodes, such as Haemonchus contortus and the invasive Ashworthius sidemi , infect a wide range of wild and domestic ruminants. While the spread of A. sidemi among European cervids has been studied, its presence in chamois ( Rupicapra rupicapra ) remains poorly documented. Conversely, H. contortus is known to infect chamois, but previous research has relied mainly on cross-sectional necropsy studies, offering only a limited view of infection dynamics. In this study, we used a longitudinal molecular approach to assess the seasonal occurrence and transmission patterns of H. contortus and A. sidemi in a chamois population from the northern Czech Republic. From January to December 2023, we collected faecal samples at monthly intervals from two localities. Multiplex real-time PCR was subsequently used for the detection and semi-quantification of DNA from both nematode species. Results: Haemonchus contortus DNA was detected in 43.3% of samples, with its presence recorded nearly year-round. Its prevalence and relative abundance peaked in summer and remained high throughout autumn. Ashworthius sidemi was identified in chamois in the Czech Republic for the first time, likely due to recent spillover from red deer ( Cervus elaphus ). However, it was found in only 5% of samples, with its occurrence restricted to late winter and spring. The seasonal disappearance of A. sidemi coincided with the increase in H. contortus abundance, suggesting a possible negative interaction between these species occupying the same ecological niche. Conclusion: Our findings indicate a prolonged transmission window for H. contortus , which may expand further with climate change. In contrast, A. sidemi appears to be an incidental parasite in chamois, and its long-term persistence in this atypical host without continued contact with cervids remains uncertain. These insights, which are rare for wild ruminants, contribute to a better understanding of parasite epidemiology and host-parasite interactions in free-living populations.