Equine herpesvirus 2-associated granulomatous dermatitis in a horse.
Authors: Sledge D G, Miller D L, Styer E L, Hydrick H A, Baldwin C A
Journal: Veterinary pathology
Summary
# Editorial Summary: Equine Herpesvirus 2-Associated Granulomatous Dermatitis Granulomatous skin disease in horses presents a diagnostic challenge, with established causes ranging from parasitic and fungal infections to bacterial pathogens, yet a significant proportion of cases remain idiopathic. This 2006 case report documents an unusual presentation of recurrent granulomatous dermatitis featuring distinctive intranuclear viral inclusions within macrophages and multinucleated giant cells, concentrated in the deep dermis with multifocal areas of necrosis and histiocytic infiltration. Electron microscopy and PCR sequencing identified the causative agent as equine herpesvirus 2 (EHV-2)—a finding that expanded the known aetiological spectrum for this disease pattern. Whilst EHV-2 is typically associated with respiratory disease and keratoconjunctivitis, its recognition as a potential trigger for granulomatous skin inflammation is clinically significant for practitioners evaluating chronic or recurrent dermatitis unresponsive to conventional antimicrobial therapy. Inclusion of EHV-2 serology or PCR in the diagnostic workup for idiopathic granulomatous skin disease, particularly when lesions persist despite appropriate treatment protocols, may reveal a viral aetiology requiring modified management strategies distinct from infectious or parasitic causes.
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Practical Takeaways
- •Consider equine herpesvirus 2 as a differential diagnosis in cases of recurrent or idiopathic granulomatous skin disease when other common etiologies have been ruled out.
- •Deep dermal biopsy with electron microscopy and PCR testing may be necessary to identify herpesvirus as a causative agent in atypical skin lesions.
- •This case highlights the value of comprehensive diagnostic pathology when clinical presentation does not fit typical parasitic, fungal, or bacterial dermatitis patterns.
Key Findings
- •Equine herpesvirus 2 was identified as a causative agent of granulomatous dermatitis in a horse through PCR sequencing and electron microscopy.
- •Histologic findings included intranuclear viral inclusions within macrophages and giant cells, with multifocal necrosis in the deep dermis.
- •This case expands the known etiologic differential diagnoses for equine granulomatous skin disease beyond parasitic, fungal, and bacterial causes.