Scanning electron microscopy and fungal culture of hoof horn from horses suffering from onychomycosis.
Authors: Apprich, Spergser, Rosengarten, Hinterhofer, Stanek
Journal: Veterinary dermatology
Summary
# Editorial Summary: Fungal Infection and Horn Structural Integrity in Equine Onychomycosis Eight horses presenting with clinical onychomycosis (sand cracks, white line disease, brittleness and bruising) underwent mycological culture and scanning electron microscopy to characterise the fungal flora and associated horn damage. All eight horses yielded keratinophilic fungi on culture, with six harbouring pathogenic species including *Trichophyton* spp and *Scopulariopsis brevicaulis*; electron microscopy revealed that horses infected with these keratinopathogenic fungi exhibited severe ultrastructural damage—including collapse of the tubular horn matrix, loss of cornified cell integrity and visible fungal infiltration—whilst samples from horses with only non-pathogenic colonisation appeared microscopically indistinguishable from sound horn. This distinction between pathogenic and non-pathogenic fungal presence suggests that not all fungi isolated from diseased hooves are causative agents; clinicians should therefore recognise that positive fungal culture alone may not indicate treatment necessity, and that *Trichophyton* and *Scopulariopsis* species warrant particular attention as drivers of structural deterioration requiring intervention. The work provides objective ultrastructural evidence supporting the role of specific keratinopathogenic fungi in compromising horn quality, offering farriers and veterinarians a biological rationale for targeted antifungal approaches in persistently problematic cases.
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Practical Takeaways
- •Fungal culture of hoof horn samples is valuable for confirming onychomycosis diagnosis; obtain samples within 6 hours of collection for optimal culture results
- •Presence of sand cracks, white line disease, and brittleness warrants mycological investigation as these are common presentations of fungal hoof infections
- •Treatment approach should differentiate between keratinopathogenic fungi (which cause structural horn damage visible on SEM) and other keratinophilic organisms, as severity of horn structural damage may influence prognosis and management strategy
Key Findings
- •All eight horses with clinical onychomycosis had keratinophilic fungal infection in hoof horn cultures
- •Keratinopathogenic fungi (Trichophyton spp and Scopulariopsis brevicaulis) were detected in six of eight horses
- •SEM revealed severe structural deterioration including disrupted tubular architecture, horny layer disruption, and cellular lysis in keratinopathogenic fungal infections
- •Horn samples without dermatophyte or Scopulariopsis infection appeared microscopically similar to healthy hoof horn