Suspected acorn toxicity in nine horses.
Authors: Smith S, Naylor R J, Knowles E J, Mair T S, Cahalan S D, Fews D, Dunkel B
Journal: Equine veterinary journal
Summary
# Acorn Toxicity in Horses: A Clinical Case Series Between 2004 and 2013, nine horses presenting to two UK referral hospitals were diagnosed with suspected acorn toxicity based on documented exposure combined with clinical signs, pathological findings, and acorn material identified in faeces or the gastrointestinal tract. The condition manifested in two distinct presentations: five horses developed haemorrhagic diarrhoea with rapid deterioration (four euthanased, one died), whilst four presented with colic secondary to large colon gas distension and displacement alongside diarrhoea (three survived medical management, one was euthanased). Post-mortem examinations revealed consistent pathology across six cases, including submucosal oedema of the caecum and large intestine, acute tubular nephrosis of the kidneys, and in four cases, severe necrohaemorrhagic and ulcerative typhlocolitis and enteritis. The variable clinical presentation and outcome suggest that whilst acorn ingestion can trigger devastating typhlocolitis with secondary acute renal failure and cardiovascular collapse, mildly affected horses may recover with intensive medical support, and disease development appears dependent on unknown individual or seasonal predisposing factors. For practitioners, this case series underscores the importance of recognising acute haemorrhagic diarrhoea and colic with renal involvement in autumn cases with pasture access to oak trees, managing aggressive fluid therapy and electrolyte replacement in affected horses, and counselling clients on the benefits of minimising acorn exposure during high-risk seasons, particularly in years when acorn drop is abundant.
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Practical Takeaways
- •Acorn ingestion in autumn can cause fatal typhlocolitis and acute renal failure; limit grazing access to acorns during acorn fall season, particularly in years with heavy acorn crops
- •Distinguish between acute haemorrhagic diarrhoea (grave prognosis, rapid decline) and colic with gas distension (better prognosis with medical management); early aggressive fluid therapy critical to manage hypovolaemia and renal dysfunction
- •Individual horses appear to have varying susceptibility to acorn toxicity despite exposure, so monitor high-risk grazing situations closely and be alert to unusual diarrhoea or colic during acorn season
Key Findings
- •9 horses with suspected acorn toxicity presented with either haemorrhagic diarrhoea (5 cases, rapid deterioration) or colic with gas distension (4 cases)
- •Post mortem findings in 6 cases included submucosal oedema of large intestine/caecum, acute tubular nephrosis, necrohaemorrhagic ulcerative typhlocolitis/enteritis, and small intestinal oedema
- •Survival rate was 33% (3 of 9 cases), with 3 of 4 colic cases responding to medical management while all 5 haemorrhagic diarrhoea cases died or were euthanased
- •Disease occurred in only a small proportion of acorn-exposed horses with increased occurrence in certain years, suggesting individual or environmental predisposing factors