The effect of administration of fenbendazole on the microbial hindgut population of the horse
Authors: CROTCH-HARVEY Laura, THOMAS Leigh-Anne, WORGAN Hilary J., DOUGLAS Jamie-Leigh, GILBY Diane E., MCEWAN Neil R.
Journal: Journal of Equine Science
Summary
# Editorial Summary: Fenbendazole and Equine Hindgut Microbiota Whilst anthelmintics like fenbendazole are routinely used to control parasitic nematodes in horses, their broader effects on the hindgut microbiome remain poorly characterised—a knowledge gap this 2018 study sought to address. Researchers administered fenbendazole to treated and control groups, then monitored faecal samples over a two-week period to quantify changes in bacterial populations, ciliate protozoa, and volatile fatty acid production using molecular and chemical analysis techniques. Treatment groups showed the expected elevated faecal egg counts, yet bacterial and ciliate populations remained largely stable across both groups, with only minor temporal fluctuations detected; crucially, short-chain fatty acid metabolite profiles were unaffected by anthelmintic administration. These findings suggest that fenbendazole—at least under the conditions studied—selectively targets parasitic nematodes without significantly disrupting commensal hindgut microorganisms or downstream fermentation metabolism. For equine practitioners, this offers reassurance that standard fenbendazole dosing protocols are unlikely to compromise microbial function or require compensatory nutritional or probiotic interventions, though individual variation and longer-term effects warrant further investigation.
Read the full abstract on PubMed
Practical Takeaways
- •Fenbendazole appears safe from a microbiota perspective—routine worming with this drug does not disrupt beneficial hindgut bacteria or ciliate populations, reducing concern about secondary digestive upset
- •The selective action of fenbendazole on parasites without broad-spectrum effects supports its continued use in standard parasite control programs without additional probiotic supplementation being necessary
- •Monitoring faecal egg count is still important to confirm treatment efficacy and parasite burden, as this study confirms fenbendazole effectively targets its intended organisms
Key Findings
- •Fenbendazole treatment did not produce significant changes in bacterial or ciliate populations in the equine hindgut beyond temporal variation
- •No detectable effects on major metabolites produced by hindgut microbiota were observed following fenbendazole administration
- •Treated animals showed high faecal egg counts relative to untreated controls, confirming parasitic infection status
- •Findings suggest fenbendazole's antimicrobial action is selective to target organisms without broader dysbiotic effects on commensal microbiota