Eosinophilic Inflammation and Equine Herpesvirus-1 Associated With Haemorrhagic Cystitis in a Horse. Case Report.
Authors: Easther Ruby, Manthorpe Eve, Woolford Lucy, Kawarizadeh Amin, Hemmatzadeh Farhid, Ferlini Agne Gustavo
Journal: Journal of equine veterinary science
Summary
Equine idiopathic haemorrhagic cystitis (EIHC) presents as acute-onset aseptic bladder inflammation without clear aetiology, yet this 2022 case report documents an unusual variant in a nine-year-old Thoroughbred with concurrent EHV-1 detection and eosinophilic infiltration—features not previously recorded together in the literature. Cystoscopic examination revealed classic ulceration and haemorrhage with hyperaemic mucosa, whilst histopathology identified a mixed inflammatory response including neutrophilic, lymphoplasmacytic, and notably eosinophilic cell populations; PCR testing of bladder tissue returned positive for equine herpesvirus-1, despite negative bacterial and fungal cultures. The gelding responded favourably to conservative management combining broad-spectrum antimicrobials with NSAIDs, achieving complete clinical resolution and marked macroscopic improvement within just 14 days. Whilst EHV-1 positivity raises questions about viral aetiology, the rapid response to anti-inflammatory therapy and overall clinical presentation align more closely with idiopathic rather than infectious cystitis, suggesting the herpesvirus may represent either secondary invasion of damaged tissue or latent viral presence rather than primary cause. The first documented case of EIHC in Australia and the inaugural report linking eosinophilic inflammation to this condition warrants further investigation into whether eosinophilic involvement indicates distinct immunological pathways—potentially fungal, parasitic, or immune-mediated—that might influence treatment decisions in similar cases.
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Practical Takeaways
- •Haemorrhagic cystitis in horses may present with EHV-1 involvement but still respond well to conservative antimicrobial and anti-inflammatory therapy without specific antiviral treatment
- •Eosinophilic inflammation in bladder cystitis may indicate viral, fungal, parasitic, or immune-mediated aetiologies and should prompt broader diagnostic investigation
- •Cystoscopy combined with histopathology and PCR testing provides valuable diagnostic information for characterizing idiopathic haemorrhagic cystitis and guiding appropriate treatment decisions
Key Findings
- •A 9-year-old Thoroughbred with haemorrhagic cystitis tested positive for EHV-1 via PCR on bladder mucosa
- •Histopathology revealed chronic active ulcerative cystitis with neutrophilic, lymphoplasmacytic, and eosinophilic inflammation, with eosinophilic infiltrates being a novel finding in EIHC
- •Complete resolution of clinical signs and significant improvement of macroscopic bladder lesions achieved within 14 days using broad-spectrum antimicrobials and NSAIDs
- •This is the first reported case of possible EIHC in Australia and the first case combining eosinophilic infiltrates with EHV-1 positivity