Equine Blood Microbiome in a Cohort of Clinically Healthy Trail Riding Horses.
Abstract: Emerging research suggests the presence of a blood microbiome in clinically healthy individuals. Characterizing bacterial composition and abundance in blood from a group of healthy horses is of clinical interest. Objective: Horses in a closed herd environment will have blood microbiomes with similarities among individuals. Methods: Twenty trail-riding horses of different breeds and ages living in relative isolation on a dry lot pasture in Colorado at 7680 ft elevation. Methods: Cross-sectional study. Blood was collected from the jugular vein into serum, blood collection, and EDTA tubes. Samples were submitted to external laboratories for microbiome analysis and routine blood tests (CBC, serum biochemistry). Results: Venous blood is not sterile in healthy horses. A total of 293 bacterial genera were identified in these samples, whereas most horses had 55 to 70 genera. The most dominant taxa were Gardnerella, Sporomusaceae, Kapabacteriales, Beijerinckiaceae, and Phascolarctobacterium. Principal coordinate analysis, investigating microbial structure diversity, identified large variability with no obvious clustering, indicating dissimilarity among bacterial populations in different horses. All blood samples contained genera with pathogenic potential for horses, such as Bacteroides spp., Clostridium spp., Peptostreptococcus spp., Streptococcus spp., and Staphylococcus spp. Conclusions: Clinically healthy horses had a diverse blood microbiome. Despite the relative isolation of the horses, their blood microbiota varied markedly among individuals. Investigating the bacteria in clinically healthy horse blood provides new insight into possible microbiome shifts that may result in clinical disease.
© 2025 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
Publication Date: 2025-04-01 PubMed ID: 40167194PubMed Central: PMC11959627DOI: 10.1111/jvim.70082Google Scholar: Lookup
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- Journal Article
Summary
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The study explores the existence and composition of a blood microbiome in healthy horses, revealing a diverse bacterial presence with significant variability between individual animals despite their shared environment.
Objective
- The objective of the study was to analyze and characterize the composition and abundance of bacteria in the blood of healthy horses, operating under the hypothesis that horses living in a closed herd environment would share similar blood microbiomes.
Methods
- Samples were obtained from twenty trail-riding horses of different breeds and ages living together in a relatively isolated area in Colorado.
- Blood was drawn from these horses from the jugular vein and put into serum, blood collection, and EDTA tubes.
- These samples were subsequently sent to external labs for microbiome analysis as well as routine blood tests, which included serum biochemistry and a complete blood count (CBC).
Results
- The research revealed that the blood of healthy horses is not sterile, finding 293 bacterial genera, with each horse usually having 55 to 70.
- The dominant taxa among these bacteria were Gardnerella, Sporomusaceae, Kapabacteriales, Beijerinckiaceae, and Phascolarctobacterium.
- Analysis of the diversity of microbial structure indicated significant variability with no apparent clustering, suggesting that despite the shared environment, the bacterial populations in the different horses were dissimilar.
- All samples also contained some bacteria with pathogenic potential for horses, including Bacteroides spp., Clostridium spp., Peptostreptococcus spp., Streptococcus spp., and Staphylococcus spp.
Conclusions
- The conclusions drawn from this study suggest that even clinically healthy horses possess a diverse blood microbiome, varying markedly among individuals in spite of their relative isolation.
- This new information on the bacteria present in the blood of healthy horses could provide valuable insights into potential shifts in the microbiome that could lead to clinical disease.
Cite This Article
APA
Simms N, Bertone JJ, Melgarejo T, O'Shea C, Linde A.
(2025).
Equine Blood Microbiome in a Cohort of Clinically Healthy Trail Riding Horses.
J Vet Intern Med, 39(3), e70082.
https://doi.org/10.1111/jvim.70082 Publication
Researcher Affiliations
- Western University of Health Sciences, College of Veterinary Medicine, Pomona, California, USA.
- Western University of Health Sciences, College of Veterinary Medicine, Pomona, California, USA.
- Western University of Health Sciences, College of Veterinary Medicine, Pomona, California, USA.
- Western University of Health Sciences, College of Veterinary Medicine, Pomona, California, USA.
- Mississippi State University, College of Veterinary Medicine, Starkville, Mississippi, USA.
- Western University of Health Sciences, College of Veterinary Medicine, Pomona, California, USA.
MeSH Terms
- Animals
- Horses / blood
- Horses / microbiology
- Cross-Sectional Studies
- Microbiota
- Male
- Female
- Bacteria / classification
- Bacteria / isolation & purification
- Bacteria / genetics
- Cohort Studies
Grant Funding
- WesternU True One Medicine Initiative
Conflict of Interest Statement
Authors declare no off‐label use of antimicrobials. The authors declare no conflicts of interest.
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