Parasitic strongyle nemabiome communities in wild ruminants in Sweden

Abstract Background Wildlife hosts may serve as reservoirs for strongyles which can be transmitted to domestic livestock. Therefore, we aimed to assess the risk for transmission of important nematode pathogens to domestic sheep in Sweden. The main aim of the study was to assess the risk for transmission of important pathogens from four wildlife hosts to domestic sheep. Methods First, fecal samples were collected from roe deer (n = 125), fallow deer (n = 106), red deer (n = 18) and mouflon (n = 13) in south central Sweden during the hunting season in 2019. Second, after fecal examination samples were cultured and the larvae were harvested, followed by DNA extractions. Third, all samples were then barcoded and processed for sequence analysis on the PacBio platform. Finally, bioinformatic sequence analysis was conducted with DADA2, while species diversity and richness as well as interactions between the different hosts were calculated and analyzed in R. Results Nematode ITS2 sequences were found in 225 of 262 (86%) samples. In total 31 taxa were identified amongst which 26 (86%) to the species level These were found in different combinations, amongst which 24 (77%) occurred in roe deer, 19 (61%) in fallow deer, 20 (65%) in red deer, and 10 (32%) in mouflon. Only five species are known to be associated with livestock (Chabertia ovina, Haemonchus contortus, Oesophagostomum venulosum, Teladorsagia circumcincta and Trichostrongylus axei). However, in the present study the relative abundance and prevalence of most of these species were low. The most striking exception was T. axei which was relatively abundant in all wildlife hosts. In addition, a wide range of wildlife specific nematodes such as Ostertagia leptospicularis and Spiculopteragia spp. were identified including the invasive nematode Spiculopteragia houdemeri which was found for the first time in red deer, fallow deer, and mouflon in Sweden. The difference in the number of shared species between mouflon and all cervids (n = 6) was less than between all three cervids (n = 8). Conclusion In contrast to our previous study with sheep, the relative abundance and prevalence of T. axei was generally much higher in wildlife than both H. contortus, and T. circumcincta which were negligible. Although the risk for cross-infections of nematodes between the studied wildlife hosts and sheep in Sweden cannot be ruled out, our findings indicate that the transmission potential appear to be relatively low for H. contortus and T. circumcincta, which are the two most pathogenic species in sheep.