Exploring shotgun metagenomic data to detect microeukaryotic pathogens in wildlife

BACKGROUND: Microeukaryotic parasites of the intestinal tract are an understudied group of organisms that infect humans and many other animals. Targeted sequencing methods focused on individual loci are usually employed for detection of these parasites, making comprehensive studies of microeukaryotic parasite diversity within hosts or other systems difficult. Exploratory approaches such as shotgun metagenomic sequencing to survey the diversity of microeukaryotic parasites in new and existing datasets are not well developed. RESULTS: Utilizing existing datasets from 12 goose fecal samples, we explored some of the benefits and challenges of using shotgun metagenome sequencing to detect microeukaryotic parasites. We demonstrated the importance of careful curation of read classification data to avoid erroneously linking pathogens to hosts or environments as unsupported classifications were common in the data and varied widely depending on analysis parameters. However, we were able to establish strong support for the presence of sequences of Eimeria and Enterocytozoon bieneusi. In addition, examination of trichomonad reads indicated that parasite reads mapping to human pathogens unlikely to colonize geese may in fact represent cryptic microeukaryotic species that are not included in existing curated databases opening new potential avenues of study. CONCLUSIONS: Taken together these findings support the idea that exploring microeukaryotic parasite diversity within shotgun metagenomic datasets can be beneficial to our understanding of the presence and diversity of these organisms in wildlife hosts.