Escherichia coli is implicated in the development and manifestation of host susceptibility to the roundworm Trichostrongylus colubriformis infections in sheep

Authors: LIU, F. - Oak Ridge Institute For Science And Education (ORISE); MCNALLY, J. - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Fleming, Damarius; INGHAM, A.B. - Commonwealth Scientific And Industrial Research Organisation (CSIRO); HUNT, P. - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Li, Robert

Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2025
Publication Date: 7/1/2025
Citation: Liu, F., Mcnally, J., Fleming, D.S., Ingham, A., Hunt, P., Li, R.W. 2025. Escherichia coli is implicated in the development and manifestation of host susceptibility to the roundworm Trichostrongylus colubriformis infections in sheep. Veterinary Research. 56. Article e133. https://doi.org/10.1186/s13567-025-01565-1.
DOI: https://doi.org/10.1186/s13567-025-01565-1

Interpretive Summary: Controlling infections by disease-causing parasitic worms is important for the sheep industry. Current dewormers for parasite control lack efficaciousness long-term because the worms become resistant to treatment. Some animals harbor natural worm resistant genes, thus utilizing a selective breeding approach presents a cost-effective strategy for parasitic control. Few biological markers are available to sheep breeders and producers that can be used for selecting worm-resistant sheep. In this study, we evaluated the possibility of gut microbes contributing to resistance by analyzing bacterial species and strains in the gut of sheep that have undergone decades of selective breeding for resistance. We uncovered specific types of bacteria when combined reliably predict worm resistance. The findings will ultimately be valuable to develop more cost-effective diagnostic tools that sheep farmers or producers could implement to select worm-resistant animals for breeding and eliminate the need for expensive genetic testing.

Technical Abstract: Applied breeding for host resistance to gastrointestinal nematodes represents a cost-effective strategy for parasitic control. While resistance is under moderate genetic influences, gut microbial components involved in the development of resistance or susceptibility remain largely unknown. Here we characterize the structure and metabolic potential of the proximal colon microbiota in unique ovine populations bred for resistance and susceptibility using a full-length 16S rRNA gene sequencing-based microbiome approach. The resistant lambs produced significantly fewer parasite eggs than susceptible animals grazing on the same pasture. Further, the resistant lambs displayed a significant reduction in worm establishment in response to a Trichostrongylus colubriformis challenge infection (P'<'0.0001; N'='20 per group). Among 32 bacterial species or strains displaying a significant difference in relative abundance between the resistant and susceptible group, E. coli was more abundant in susceptible lambs. E. coli was also ranked as the most important species in distinguishing the resistant and susceptible status. Moreover, a microbial signature or balance consisting of E. coli (Numerator) and Parabacteroides distasonis and Bacteroides thetaiotaomicron (Denominator) predicted the resistance status with high accuracy. The metagenome function prediction also revealed that several pathways related to infectious diseases, such as Shigellosis and pathogenic E. coli infection, were significantly altered between the two phenotypes. Our findings demonstrated that microbial signatures with a high predictive power for the resistance status can be developed as biomarkers to facilitate the selection for host resistance in sheep.