Pseudallescheria boydii keratomycosis in a horse.

This study presents a case of horse keratomycosis caused by the fungal organism Pseudallescheria boydii. Despite efforts to treat the condition with a range of antifungal drugs, it proved drug-resistant, leading to a stromal abscess in the cornea and eventual removal of the eye.

Fungal Organism Isolation

• The research discusses an instance where the fungal organism Pseudallescheria boydii was identified in the cornea of a Quarter Horse battling ulcerative keratitis – an inflammation and ulceration of the cornea.

Treatment Attempts

• Despite administering hourly medication through a subpalpebral lavage system – a fluid irrigation and drainage technique – using drugs like miconazole and natamycin, the cornea developed a stromal abscess.
• An abscess in the cornea’s stroma layer indicates a bacterial or fungal infection. In this case, Pseudallescheria boydii infection was brewing.
• The unsuccessful drug therapy required an orbital exenteration – a surgical operation to remove the eye – after three weeks due to the escalating condition.

Drug Resistance

• The fungus was tested against eight different antifungal drugs, and it demonstrated resistance to all.
• This resistance suggests a high adaptability of Pseudallescheria boydii, making infection treatments a challenge.

Microscopic Examination

• A microscopic analysis of the cornea confirmed the presence of Pseudallescheria boydii, with fungal hyphae – thread-like structures of a fungus – seen throughout the cornea’s stroma and penetrating the Descemet membrane, the innermost layer of the cornea.

Previous Cases

• This specific organism has not been previously associated with keratomycosis – a fungal infection of the cornea – in horses or any other domestic animals. However, the fungus has been identified in human keratomycosis cases.
• This discovery indicates the possibility of the fungus crossing species barriers, which could have significant implications for animal and perhaps human health.