Subconjunctival mycetoma caused by Scedosporium apiospermum infection in a horse.

An 11-year-old horse was found to have a nonpainful eye mass due to an infection from the fungus Scedosporium apiospermum, leading to the discovery of an important veterinary and human pathogen that often resists common antifungal treatment.

Case Presentation and Findings

• An American Saddlebred gelding aged 11 years had a nonpainful mass below the conjunctiva of the left eye.
• Other ocular abnormalities included a central corneal scar and a small central cataract in the same eye.
• Cytologic examination of a fine-needle aspirate from the mass revealed inflammation and intralesional fungal hyphae, typical of a mycetoma.
• Fungal structures were elongated with nonstaining walls; bulbous yeast-like structures were also apparent.
• The mycetoma was surgically removed for further evaluation.

Further Diagnostic Investigations

• Following its removal, the mycetoma was subjected to histopathologic examination and fungal culture.
• The histopathology confirmed subconjunctival phaeohyphomycosis, a fungal infection of the subconjunctival tissue.
• Culture of the tissue identified the fungus Scedosporium apiospermum, characterized by its macroscopic and microscopic structures.
• Scedosporium spp. have been reported to cause these types of infections in humans and animals, regardless of their immune status.
• The identified S. apiospermum, alongside its teleomorphic counterpart Pseudallescheria boydii, are emerging as potential human and veterinary pathogens.

Importance of Timely Diagnosis and Treatment

• This fungus is often resistant to commonly used antifungal drugs, highlighting the importance of an immediate diagnosis to facilitate appropriate treatment.
• According to the report, the case provides a detailed cytologic characterization of the organism, alongside up-to-date information on its taxonomy.
• The publication also discusses the diagnostic peculiarities of this particular infection.