When Colic Becomes Critical: A New Equine Sepsis Diagnostic Score for Horses
A new study of 295 horses with colic has produced the first validated diagnostic scoring system for sepsis in adult horses — using six routine clinical measurements that most equine vets can obtain on arrival.
Colic is one of the most feared emergencies in horse ownership, and for good reason: it is a leading cause of death in horses worldwide. Most colic cases resolve with medical treatment, but a significant subset progress to something far more dangerous — sepsis, the body's catastrophic, dysregulated response to infection. When colic leads to intestinal rupture, severe ischemia, or infectious diarrhea, bacteria and endotoxins can flood the bloodstream, triggering organ dysfunction that kills horses quickly.
The challenge facing veterinarians has always been identifying that turning point early enough to act. Until now, no validated equine sepsis diagnostic score existed for adult horses. This study, published in Animals in March 2026, set out to change that.
Overview
Researchers at Oniris VetAgroBio in Nantes, France, conducted a ten-year retrospective analysis of horses admitted for colic to their equine emergency department. From an initial pool of 798 horses, 295 met the inclusion criteria: adult horses with confirmed gastrointestinal disease and sufficient clinical data, classified definitively as either colic (no sepsis, N = 206) or sepsis (N = 89).
The sepsis group was defined rigorously: confirmed infectious peritonitis, advanced ischemic intestinal injury, intestinal rupture, or confirmed infectious diarrhea — all in horses showing clinical signs of cardiovascular shock. The colic group included straightforward cases: displacements, impactions, simple obstructions, and gastric conditions with no systemic infection.
Researchers analyzed every available clinical and laboratory parameter collected at admission, ran univariate logistic regression to identify which individual variables were associated with sepsis, then used multivariate modeling to find the combination that best predicted it as a composite. The goal was a score a clinician could calculate quickly in the field — no complex equipment, no parameters only available post-surgery or in intensive care.
Key findings: How the equine sepsis diagnostic score works
Sepsis was more common than expected. Roughly 30% of horses admitted for colic in this cohort were ultimately diagnosed with sepsis — a striking prevalence that underscores how frequently the condition presents in an emergency colic population.
Six parameters built the score. After multivariate analysis, six variables emerged as the strongest composite predictors of sepsis:
Parameter | Abnormal Threshold | Score Points |
Rectal temperature (°C) | <36 or >38.5 | 2 |
Heart rate (bpm) | >52 | 1 |
Leukocyte count (cells/µL) | <5,000 or >12,500 | 2 |
Red blood cell count (cells/µL) | <5.5 or >12.5 | 1 |
Creatine kinase (U/L) | >250 | 1 |
Blood lactate (mmol/L) | >2 | 1 |
The total score is the sum of all applicable points, with a maximum of 8.
Two thresholds serve different clinical needs. A score of 2 or above offers higher sensitivity (77%) — useful for not missing cases — but lower specificity (75%). A score of 3 or above is highly specific (91.6%), meaning it is more reliable for confirming sepsis when present. The overall model accuracy was 79%.
Elevated creatine kinase was a standout finding. CK is not a marker typically associated with sepsis, but it emerged as independently predictive in this dataset. The researchers note this may reflect musculoskeletal consequences of severe illness — prolonged recumbency, struggling, or possible cardiac muscle involvement — as well as the severity of intestinal ischemia itself, since CK has been linked to strangulating small intestinal lesions.
Ponies were overrepresented in the sepsis group. While warmblood horses made up the majority of the colic-only group (65.8%), ponies were significantly overrepresented among septic horses (44% vs. 17.8%). The researchers did not draw firm conclusions from this, but it warrants attention — particularly given existing evidence that ponies may respond differently to systemic disease.
Leukopenia and leukocytosis both predicted sepsis. Rather than just elevated white cell counts, both abnormally low and abnormally high leukocyte counts were associated with sepsis. This bidirectional relationship reflects the complex immune dynamics of systemic infection — early overwhelming infection can drive leukopenia as cells are rapidly consumed.
How to apply this in your barn and with your vet
Know the six numbers. When a horse presents with colic severe enough to warrant veterinary evaluation, these are the six values that matter most for identifying whether the situation may be turning septic: temperature, heart rate, white cell count, red cell count, creatine kinase, and blood lactate. Most of these are part of a standard emergency workup — but knowing why they matter helps you understand what your vet is looking for.
Sepsis doesn't always look obvious. A horse with sepsis secondary to colic may not look dramatically different from one with severe, non-septic colic — especially in the first hours. This is precisely why a scoring tool matters. Do not wait for a horse to "look septic" before calling for emergency evaluation. Early intervention is what saves lives.
Be honest with your vet about what happened before they arrived. Pre-treating with NSAIDs before the vet arrives is common practice, but the researchers note it can mask fever and lower heart rate — both key parameters in this score. Tell your vet exactly what was given, when, and at what dose. This context helps them interpret the clinical picture accurately.
Ponies and older horses may warrant extra vigilance. The data suggest ponies may be disproportionately affected by septic colic complications. If you have a pony presenting with severe colic, communicate clearly and quickly, and do not assume smaller body size means a smaller problem.
This score is a veterinary tool — but understanding it makes you a better advocate. You can't calculate leukocyte counts at home, but you can recognize that a horse with a very high fever, a heart rate above 52 bpm at rest, and obvious signs of pain is presenting with multiple red flags simultaneously. When multiple parameters are abnormal at once, the urgency multiplies — not just adds.
Ask your vet whether bloodwork is indicated. In a colic emergency, it may feel like the priority is treatment, not testing. But this study shows that a simple blood panel — something many equine vets can run quickly at the clinic — provides critical information that can't be approximated by clinical signs alone. Advocacy for comprehensive workup, even when cost is a concern, can change outcomes.
Read the study
Blangy-Letheule, A., Montnach, J., Perrier, J., Lemonnier, L. C., Denis, M., Rozec, B., Lauzier, B., & Leroux, A. A. (2026). New diagnostic score for sepsis in adult horses with acute gastrointestinal disease. Animals, 16(6), 962. https://doi.org/10.3390/ani16060962
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