Death of a horse infected experimentally with Anaplasma phagocytophilum.
Authors: Franzén P, Berg A-L, Aspan A, Gunnarsson A, Pringle J
Journal: The Veterinary record
Summary
# Editorial Summary This case report documents the fatal progression of Anaplasma phagocytophilum infection in a 19-year-old horse during an experimental pathogenesis study, demonstrating that whilst clinical signs and laboratory abnormalities were initially indistinguishable from those observed in five surviving cohorts, acute deterioration and death occurred within 48 hours of symptom onset. Postmortem findings revealed disseminated intravascular coagulation (DIC), characterised by widespread haemorrhage affecting multiple organs and vascular pathology including thrombosis and vasculitis in the kidneys—a presentation previously documented only in human granulocytic ehrlichiosis. The severity of DIC in this case suggests that individual variation in disease progression exists among horses exposed to identical infection conditions, highlighting that some animals may develop fulminant complications despite normal early clinical and laboratory parameters. For equine practitioners, this underscores the importance of close clinical monitoring during the acute phase of A. phagocytophilum infection and recognition that rapidly deteriorating cases warrant aggressive supportive care; the potential for coagulopathy development should inform clinical decision-making even when initial presentations appear stable relative to other affected horses.
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Practical Takeaways
- •Anaplasma phagocytophilum infection can rapidly progress to fatal disseminated intravascular coagulation; clinical signs alone may not predict severity or outcome
- •Awareness of this pathogen is important for equine practitioners as it can cause acute death despite initial clinical presentation resembling less severe cases
- •Vasculitis and thrombosis warrant consideration in differential diagnoses for sudden deterioration in horses presenting with granulocytic ehrlichiosis signs
Key Findings
- •A 19-year-old horse died suddenly two days after onset of clinical signs of A. phagocytophilum infection despite clinical presentation similar to other infected horses in the experimental group
- •Postmortem examination revealed widespread haemorrhaging in internal organs with vasculitis and thrombosis in the kidneys
- •Pathological findings are consistent with disseminated intravascular coagulation, previously reported in humans with the same agent