Ultraviolet C (UV-C) Light Therapy for Equine Ulcerative Keratomycosis-An In Vitro Study.

Area of Science:

• Veterinary Ophthalmology
• Mycology
• Antimicrobial Technology

Background:

• Equine keratomycosis is a significant cause of vision impairment in horses.
• Fungal keratitis is often treated with topical antifungal medications, which can have side effects.
• Ultraviolet C (UV-C) light offers a potential non-invasive antimicrobial treatment modality.

Purpose of the Study:

• To evaluate the efficacy of a commercially available 275 nm UV-C device in inhibiting equine fungal pathogens in vitro.
• To determine the optimal UV-C exposure time and dose for antifungal effect against Aspergillus and Fusarium species.
• To correlate UV-C treatment parameters with potential corneal safety.

Main Methods:

• Fungal isolates of Aspergillus and Fusarium spp. were exposed to UV-C light at varying distances (10, 15, 20 mm) and durations (5-30 s) with single or repeat doses.
• Inhibition zone sizes were measured microscopically after 24, 48, and 72 hours of incubation.
• Regrowth checks were performed to assess the complete eradication of fungi.

Main Results:

• Significant fungal inhibition was observed with UV-C doses as low as 5 s/7.5 mJ/cm² at 10 mm and 10 s/7 mJ/cm² at 20 mm.
• Increasing UV-C exposure from 5 s to 15 s at 10 mm significantly enlarged inhibition zones for all isolates.
• A 15 s exposure at 10 mm resulted in comparable inhibition zone sizes across different fungal isolates, though increased distance led to more regrowth.

Conclusions:

• An in vitro UV-C exposure of 15 s at a 10 mm distance (22.5 mJ/cm²) appears to be an optimal dose for inhibiting Aspergillus and Fusarium spp.
• This UV-C dose may align with previously reported corneal safety thresholds.
• Further preclinical and clinical safety studies are necessary to validate the therapeutic potential of UV-C for equine fungal keratitis.