Characterization of the intestinal microbiota of Holstein Fasciola-positive and -negative cattle from a hyperendemic area of fascioliasis in central Colombia

The ability to identify compositional changes in the intestinal microbiota of parasitized hosts is important for understanding the physiological processes that may affect animal productivity. Within the field of host–parasite interactions, many studies have suggested that helminths can influence the microbial composition of their hosts via their immunomodulatory effects. Bovine fascioliasis is a helminthiasis widely studied by immunologists, but with little information available in the research field of host–helminth interactions, the impact of fascioliasis on microbial communities is unclear. Thus, we aimed to describe the composition of the intestinal microbiota of Holstein Fasciola-positive and -negative cattle using parasitological methods and ELISA (enzyme-linked immunosorbent assay). Fecal samples from these cattle (n=65), which were obtained from grazing lands in the Cundi-Boyacense Colombian highlands (a hyperendemic region for bovine fascioliasis), were subjected to amplicon-based next-generation 16S-rRNA and 18S-rRNA gene sequencing. From these samples, 35 were Fasciola hepatica-negative and 30 were F. hepatica-positive in our detection analysis. We found a reduction in the relative abundance of Bacteroidetes and Ascomycota in the Fasciola-positive samples, along with decreased relative abundances of the commensal taxa associated with fermentation and digestion processes. Positive correlations were also found among the microorganisms that showed reduced relative abundances in the Fasciola-positive samples, the animals of which showed weight losses consistent with the phenotype of cattle infected with this parasite. We therefore conclude that cattle infected with F. hepatica have a decreased ability to digest plant material as a consequence of the reduced abundance of taxa responsible for this function. These findings are a small first step in the development of research aimed at understanding how microbial populations are modulated in F. hepatica infections.