Acute Equine Diarrhoea: What Does Current Clinical Practice Tell Us?

Acute diarrhoea remains one of the most challenging emergencies in equine medicine. While clinicians often focus on stabilising dehydration, preventing endotoxaemia, and reducing complications such as laminitis, a recent large multicentre international study has revealed an important reality: treatment approaches vary considerably between hospitals, often in the absence of strong evidence-based guidelines¹. 

Antimicrobials: Are We Using Them Too Often? 

One of the most striking findings was that 55% of horses received antimicrobial therapy within the first 24 hours of admission. While horses with leukopenia or systemic inflammatory response syndrome (SIRS) were more likely to receive antimicrobials, nearly half of the horses without leukopenia also received treatment¹. 

This raises an important stewardship question. Most causes of acute equine diarrhoea are not associated with bacterial pathogens that require antimicrobial therapy, with Neorickettsia risticii being a notable exception^2,3. Yet broad-spectrum combinations such as penicillin and gentamicin remain common. 

Although antimicrobial use is not inappropriate, there is a need for clear guidelines defining which patients would truly benefit. Until prospective studies become available, antimicrobial administration should perhaps be reserved for horses showing evidence of systemic compromise, bacterial translocation, or confirmed bacterial infection¹. 

Fluid Therapy: Evidence Still Lags Behind Practice 

Fluid therapy was predictably central to treatment. However, the study highlights a surprising gap between common practice and available evidence. 

Hypertonic saline, crystalloid boluses, synthetic colloids, and plasma transfusions were all used regularly, particularly in more severely affected horses. Yet for many of these interventions, robust evidence demonstrating improved survival or clinical outcomes in diarrhoeic horses is lacking ^1,4. 

Perhaps most noteworthy is the frequent use of crystalloid boluses in horses not considered clinically dehydrated. Human critical care research increasingly recognises the risks of fluid overload, but comparable equine data remain scarce¹. 

The message is not that fluids should be restricted, but rather that veterinarians should continually reassess fluid requirements instead of assuming that more fluid automatically translates into better outcomes. 

Not All Adjunctive Therapies Are Equal 

Therapies such as gastroprotectants, probiotics, toxin-binding agents, polymyxin B, plasma, and pentoxifylline are biologically plausible and widely accepted in practice. However, their supporting evidence varies considerably. 

For example, probiotics were administered to 15% of horses despite ongoing concerns regarding product quality, microbial viability, and inconsistent clinical efficacy1,3,5. Similarly, gastroprotectants were used in nearly half of cases, even though gastric ulceration may not be a common finding in horses with colitis¹. 

In contrast, digital cryotherapy stands out as one intervention with relatively strong evidence supporting its role in reducing the incidence and severity of laminitis associated with colitis^1,6. 

The Bigger Picture: A Need for Standardised Guidelines 

Perhaps the most important takeaway is not whether a particular therapy is right or wrong. Instead, the study demonstrates substantial variation in treatment approaches between institutions, suggesting that many clinical decisions are influenced by tradition, individual experience, or local protocols rather than definitive evidence. 

For practitioners, this reinforces the importance of regularly reviewing emerging literature, questioning long-standing habits, and balancing intervention with evidence. 

As equine medicine continues to embrace antimicrobial stewardship and evidence-based practice, studies such as this provide a valuable benchmark of where the profession currently stands—and where future research needs to focus. 

Clinical Pearl 

When managing acute diarrhoea, interventions supported by strong evidence should remain the foundation of treatment, while therapies with limited outcome data should be used thoughtfully and tailored to the individual patient rather than applied routinely. 

References  

1. Gomez DE, Kopper JJ, Byrne DP, Renaud DL, Schoster A, Dunkel B, Arroyo LG, Mykkanen A, Gilsenan WF, Pihl TH, Lopez-Navarro G. Treatment approaches to horses with acute diarrhea admitted to referral institutions: A multicenter retrospective study. PloS one. 2024 Nov 20;19(11):e0313783. https://doi.org/10.1371/journal.pone.0313783  

2. Shaw SD, Stämpfli H. Diagnosis and treatment of undifferentiated and infectious acute diarrhea in the adult horse. The Veterinary clinics of North America. Equine practice. 2018 Feb 14;34(1):39. https://doi.org/10.1016/j.cveq.2017.11.002  

3. Arroyo LG, Moore A, Bedford S, Gomez DE, Teymournejad O, Xiong Q, Budachetri K, Bekebrede H, Rikihisa Y, Baird JD. Potomac horse fever in Ontario: Clinical, geographic, and diagnostic aspects. The Canadian Veterinary Journal. 2021 Jun;62(6):622. https://pmc.ncbi.nlm.nih.gov/articles/PMC8118184/  

4. Tavanaeimanesh H, Dezfouli MM, Vajhi A, Rostam A, Akbarinejad V, Sadeghian Chaleshtori S, Corley KT. The effect of 7.2% hypertonic saline solution on echocardiographic parameters of healthy horses. Equine veterinary journal. 2015 Nov;47(6):741-4. https://doi.org/10.1111/evj.12496  

5. Dunkel B, Johns IC. Antimicrobial use in critically ill horses. Journal of veterinary emergency and critical care. 2015 Jan;25(1):89-100. https://onlinelibrary.wiley.com/doi/10.1111/vec.12275  

6. Burke MJ, Tomlinson JE, Blikslager AT, Johnson AL, Dallap‐Schaer BL. Evaluation of digital cryotherapy using a commercially available sleeve style ice boot in healthy horses and horses receiving iv endotoxin. Equine veterinary journal. 2018 Nov;50(6):848-53. https://doi.org/10.1111/evj.12842https://doi.org/10.1111/evj.12842