Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Ultraviolet C (UV-C) Light Therapy Inhibits Pathogens Associated With Equine Keratomycosis at Different Corneal Depths-An Ex Vivo Study.
Abstract: To assess if an inexpensive, commercially available ultraviolet C (UV-C) light device with a peak emission of 275 nm can inhibit equine keratomycosis-associated pathogens located at different corneal depths in an ex vivo model. Methods: A controlled, randomized experimental design. Aspergillus fumigatus and Fusarium solani isolates were inoculated in fresh bovine corneoscleral transplants, superficially or at 450 μm of stromal depth for the ulcerative keratomycosis or stromal abscess model, respectively. After a minimum of 18 h of incubation, treatment groups received 15 s of UV-C light exposure at a 10 mm distance from the corneal surface level (22.5 mJ/cm dose). Fungal inactivation was quantified by determining the mean fluorescent intensity (MFI) of two fungal viability markers (SYTO 9 = green = alive; PI = red = dead) utilizing confocal laser scanning microscopy. Results: UV-C treatment resulted in statistically significantly higher MFI-PI, lower MFI-SYTO 9 and lower normalized MFI ratios (SYTO 9/[SYTO 9 + PI]) compared to controls for both isolates irrespective of corneal depth; therefore demonstrating successful fungal inactivation. In superficial location, fungal inhibition reached 88% for both isolates. At deeper corneal depth, fungal inhibition was not significantly different for F. solani (84%) but significantly less complete for A. fumigatus (60%). Conclusions: Corneal UV-C light treatment may offer therapeutic benefits for ulcerative keratomycosis and stromal abscesses in the equine species using doses expected to be safe for corneal exposure based on previously published safety data. Species-specific safety studies are required to ensure that antifungal efficacy aligns with safe clinical practice.
© 2025 The Author(s). Veterinary Ophthalmology published by Wiley Periodicals LLC on behalf of American College of Veterinary Ophthalmologists.
Publication Date: 2025-12-15 PubMed ID: 41399192PubMed Central: PMC12963518DOI: 10.1111/vop.70110Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
Overview
- This study evaluated whether a commercially available UV-C light device can inhibit fungal pathogens causing equine keratomycosis at varying depths within the cornea using an ex vivo bovine corneal model.
- The research demonstrated that UV-C light effectively inactivated key fungal pathogens, Aspergillus fumigatus and Fusarium solani, both superficially and at deeper stromal layers important for ulcerative keratomycosis and stromal abscesses.
Background and Purpose
- Equine keratomycosis is a fungal infection of the cornea, often difficult to treat because fungi can penetrate deep into the stromal layers.
- Current treatments may be limited or expensive; therefore, inexpensive and accessible methods like UV-C light therapy are being explored.
- UV-C light, with a peak emission around 275 nm, has known antimicrobial properties but its efficacy at various corneal depths and its safety profile in equine eyes required evaluation.
- The study aimed to assess whether UV-C light could inhibit fungal pathogens associated with keratomycosis at superficial and deep stromal corneal depths using an ex vivo model.
Methods
- Experimental Design: Controlled randomized setup using fresh bovine corneoscleral transplants to simulate the equine cornea.
- Pathogens Studied: Aspergillus fumigatus and Fusarium solani, both common fungi implicated in equine keratomycosis.
- Inoculation:
- Superficial inoculation modeled ulcerative keratomycosis with fungi placed on the corneal surface.
- Deeper inoculation placed fungi 450 μm into the stroma to simulate stromal abscesses.
- Incubation: At least 18 hours allowed fungal growth within the corneal tissue before treatment.
- UV-C Treatment:
- Exposure to UV-C light at 275 nm for 15 seconds.
- Light source positioned 10 mm from corneal surface delivering 22.5 mJ/cm² dose.
- Fungal Viability Assessment:
- Use of two fluorescent markers:
- SYTO 9 (green) stains live fungal cells.
- Propidium Iodide (PI, red) stains dead fungal cells.
- Confocal laser scanning microscopy measured Mean Fluorescent Intensity (MFI) for each marker to quantify fungal viability.
- Normalized ratios (SYTO 9 / [SYTO 9 + PI]) allowed comparison between treated and control samples.
- Use of two fluorescent markers:
Results
- UV-C treatment showed statistically significant:
- Higher red fluorescence (MFI-PI), indicating increased fungal death.
- Lower green fluorescence (MFI-SYTO 9), indicating decreased live fungi.
- Lower normalized live-to-total fluorescence ratios, affirming fungal inactivation.
- Superficial Fungal Location:
- Both Aspergillus fumigatus and Fusarium solani showed approximately 88% inhibition after UV-C exposure.
- Deeper Stromal Location:
- Fusarium solani inhibition was similar to superficial (around 84%), indicating UV-C penetrated effectively.
- Aspergillus fumigatus inhibition was reduced but still significant at about 60%, suggesting some limitation in UV-C penetration or fungal resistance at depth.
Conclusions and Implications
- UV-C light at the tested dose and exposure time effectively inactivated keratomycosis-associated fungi in corneal tissue both superficially and within the stroma.
- This suggests potential for UV-C therapy as a cost-effective treatment alternative or adjunct for equine corneal fungal infections like ulcerative keratomycosis and stromal abscesses.
- The UV-C dose used aligns with previously reported safety data, indicating potential clinical safety for corneal exposure.
- However, species-specific safety and efficacy studies are necessary before clinical application to ensure both antifungal effect and ocular safety in horses.
- Future research should focus on in vivo testing, dosage optimization, and evaluating long-term corneal health post UV-C treatment.
Cite This Article
APA
Hoerdemann M, Sahoo DK, Allbaugh RA, Kubai MA.
(2025).
Ultraviolet C (UV-C) Light Therapy Inhibits Pathogens Associated With Equine Keratomycosis at Different Corneal Depths-An Ex Vivo Study.
Vet Ophthalmol, 29(2), e70110.
https://doi.org/10.1111/vop.70110 Publication
Researcher Affiliations
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA.
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA.
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA.
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA.
MeSH Terms
- Animals
- Horses
- Horse Diseases / microbiology
- Horse Diseases / radiotherapy
- Fusarium / radiation effects
- Aspergillus fumigatus / radiation effects
- Cattle
- Ultraviolet Rays
- Keratitis / veterinary
- Keratitis / microbiology
- Keratitis / radiotherapy
- Ultraviolet Therapy / veterinary
- Fusariosis / veterinary
- Fusariosis / radiotherapy
- Fusariosis / microbiology
- Eye Infections, Fungal / veterinary
- Eye Infections, Fungal / radiotherapy
- Eye Infections, Fungal / microbiology
- Cornea / microbiology
- Cornea / radiation effects
- Aspergillosis / veterinary
- Aspergillosis / radiotherapy
- Aspergillosis / microbiology
Grant Funding
- 028567-00001 / International Equine Ophthalmology Consortium
- CVM PG105121 / Iowa State University
Conflict of Interest Statement
The authors have not used AI to generate any part of the manuscript. Stockyard consent for the harvest and use of ocular tissues for research purposes was obtained. The authors received approval (IBC‐23‐006) from the Iowa State University Institutional Biosafety Committee for the study. Prior to further processing, a brief ophthalmic examination was conducted by an ophthalmology resident (MH) to examine the globes for any evidence of trauma or pre‐existing corneal or intraocular disease that led to exclusion from the study. The authors declare no conflicts of interest.
References
This article includes 41 references
- Martinez P. S., Whitley R. D., Plummer C. E., Richardson R. L., Hamor R. E., Wellehan J. F. X.. In Vitro Antifungal Susceptibility of Species and Cultured From Eleven Horses With Fungal Keratitis. Veterinary Ophthalmology 25, no. 5 (2022): 376–384.
- Smith H. L., Love K. R., Antezana A., Barr E. M., Gilger B. C., Oh A.. Treatment of Equine Keratomycosis, Part 2: Reporting Common Systemic and Ocular Complications to Enhance Decision‐Making for Equine Clinicians and Owners. Journal of the American Veterinary Medical Association 262, no. S2 (2024): S85–S93.
- Andrew S. E., Brooks D. E., Smith P. J., Gelatt K. N., Chmielewski N. T., Whittaker C. J. G.. Equine Ulcerative Keratomycosis: Visual Outcome and Ocular Survival in 39 Cases (1987–1996). Equine Veterinary Journal 30, no. 2 (1998): 109–116.
- Galán A., Martín‐Suárez E. M., Gallardo J. M., Molleda J. M.. Clinical Findings and Progression of 10 Cases of Equine Ulcerative Keratomycosis (2004–2007). Equine Veterinary Education 21, no. 5 (2009): 236–242.
- Gaarder J. E., Rebhun W. C., Ball M. A., Patten V., Shin S., Erb H.. Clinical Appearances, Healing Patterns, Risk Factors, and Outcomes of Horses With Fungal Keratitis: 53 Cases (1978‐1996). Journal of the American Veterinary Medical Association 213, no. 1 (1998): 105.
- Pearce J. W., Giuliano E. A., Moore C. P.. In Vitro Susceptibility Patterns of and Species Isolated From Equine Ulcerative Keratomycosis Cases in the Midwestern and Southern United States With Inclusion of the New Antifungal Agent Voriconazole. Veterinary Ophthalmology 12, no. 5 (2009): 318–324.
- Uchida‐Fujii E., Kuroda T., Niwa H.. Bacterial and Fungal Isolates From 107 Cases of Ulcerative Keratitis in Japanese Thoroughbred Racehorses (2017–2021). Journal of Equine Veterinary Science 133 (2024): 104990.
- Brooks D. E., Andrew S. E., Dillavou C. L., Ellis G., Kubilis P. S.. Antimicrobial Susceptibility Patterns of Fungi Isolated From Horses With Ulcerative Keratomycosis. American Journal of Veterinary Research 59, no. 2 (1998): 138.
- Adams V. J., Campbell J. R., Waldner C. L., Dowling P. M., Shmon C. L.. Evaluation of Client Compliance With Short‐Term Administration of Antimicrobials to Dogs. Journal of the American Veterinary Medical Association 226, no. 4 (2005): 567–574.
- Smith H. L., Love K. R., Antezana A., Barr E. M., Gilger B. C., Oh A.. Treatment of Equine Keratomycosis, Part 1: Selection of Appropriate Therapy Based on Clinical Presentation and Diagnostic Testing Improves Clinical Outcomes. Journal of the American Veterinary Medical Association 262, no. S2 (2024): S74–S84.
- Marasini S., Craig J. P., Dean S. J., Leanse L. G.. Managing Corneal Infections: Out With the Old, in With the New?. Antibiotics 12, no. 8 (2023): 1334.
- Marasini S., Dean S. J., Swift S.. Preclinical Confirmation of UVC Efficacy in Treating Infectious Keratitis. Ocular Surface 25 (2022): 76–86.
- Marasini S., Mugisho O. O., Swift S.. Effect of Therapeutic UVC on Corneal DNA: Safety Assessment for Potential Keratitis Treatment. Ocular Surface 20 (2021): 130–138.
- Marasini S.. Exploring the Potential of UVC in Treating Superficial Corneal Infections (PhD Thesis). University of Auckland, 2019.
- Turicea B., Sahoo D. K., Allbaugh R. A., Stinman C. C., Kubai M. A.. Novel Treatment of Infectious Keratitis in Canine Corneas Using Ultraviolet C (UV‐C) Light. Veterinary Ophthalmology 2024 (2024): 1–713.
- Hoerdemann M, Sahoo D K, Allbaugh R A, Kubai M A. Ultraviolet C (UV‐C) Light Therapy for Equine Ulcerative Keratomycosis—An In Vitro Study. Veterinary Ophthalmology 2025 (2025): 1–14.
- Mallet J D, Dorr M M, Desgarnier M C D, Bastien N, Gendron S P, Rochette P J. Faster DNA Repair of Ultraviolet‐Induced Cyclobutane Pyrimidine Dimers and Lower Sensitivity to Apoptosis in Human Corneal Epithelial Cells Than in Epidermal Keratinocytes. PLoS One 11, no. 9 (2016): e0162212.
- Song C, Wen R, Zhou J. UV C Light From a Light‐Emitting Diode at 275 Nanometers Shortens Wound Healing Time in Bacterium‐ and Fungus‐Infected Skin in Mice. Microbiology Spectrum 10, no. 6 (2022): e0342422.
- Kaidzu S, Sugihara K, Sasaki M. Re‐Evaluation of Rat Corneal Damage by Short‐Wavelength UV Revealed Extremely Less Hazardous Property of Far‐UV‐C. Photochemistry and Photobiology 97, no. 3 (2021): 505–516.
- Mallet J D, Rochette P J. Wavelength‐Dependent Ultraviolet Induction of Cyclobutane Pyrimidine Dimers in the Human Cornea. Photochemical & Photobiological Sciences 12, no. 8 (2013): 1310–1318.
- Hamilton H L, McLaughlin S A, Whitley E M, Gilger B C, Whitley R D. Histological Findings in Corneal Stromal Abscesses of 11 Horses: Correlation With Cultures and Cytology. Equine Veterinary Journal 26, no. 6 (1994): 448–453.
- Welch P M, Gabal M, Betts D M, Whelan N C, Studer M E. In Vitro Analysis of Antiangiogenic Activity of Fungi Isolated From Clinical Cases of Equine Keratomycosis. Veterinary Ophthalmology 3 (2000): 145–151.
- De Linde Henriksen M, Andersen P H, Plummer C E, Mangan B, Brooks D E. Equine Corneal Stromal Abscesses: An Evolution in the Understanding of Pathogenesis and Treatment During the Past 30 Years. Equine Veterinary Education 25, no. 6 (2013): 315–323.
- De Linde Henriksen M, Andersen P H, Mietelka K. Equine Deep Stromal Abscesses (51 Cases—2004–2009)—Part 2: The Histopathology and Immunohistochemical Aspect With Attention to the Histopathologic Diagnosis, Vascular Response, and Infectious Agents. Veterinary Ophthalmology 17, no. S1 (2014): 14–22.
- Shihan M H, Novo S G, Le Marchand S J, Wang Y, Duncan M K. A Simple Method for Quantitating Confocal Fluorescent Images. Biochemistry and Biophysics Reports 25 (2021): 100916.
- Shailaja A, Bruce T F, Gerard P, Powell R R, Pettigrew C A, Kerrigan J L. Comparison of Cell Viability Assessment and Visualization of Biofilm With Two Fluorescent Probe Staining Methods. Biofilms 4 (2022): 100090.
- Ledbetter E C, Irby N L, Kim S G. In Vivo Confocal Microscopy of Equine Fungal Keratitis. Veterinary Ophthalmology 14, no. 1 (2011): 1–9.
- Stiefel P, Schmidt‐Emrich S, Maniura‐Weber K, Ren Q. Critical Aspects of Using Bacterial Cell Viability Assays With the Fluorophores SYTO9 and Propidium Iodide. BMC Microbiology 15, no. 1 (2015): 36.
- Lu J, Turnbull L, Burke C. Manuka‐Type Honeys Can Eradicate Biofilms Produced by Strains With Different Bio‐Film Forming Abilities. PeerJ 2 (2014): e326.
- Martabano B B, De Linde Henriksen M, Powell C C. Prevalence of Equine Ulcerative Keratomycosis in Colorado and Association of Environmental Factors: A Retrospective and Descriptive Study (2002–2017). Equine Veterinary Education 33, no. 1 (2021): 24–30.
- Andrew S E, Nguyen A, Jones G L, Brooks D E. Seasonal Effects on the Aerobic Bacterial and Fungal Conjunctival Flora of Normal Thoroughbred Brood Mares in Florida. Veterinary Ophthalmology 6, no. 1 (2003): 45–50.
- Reed Z, Thomasy S M, Good K L. Equine Keratomycoses in California From 1987 to 2010 (47 Cases). Equine Veterinary Journal 45, no. 3 (2013): 361–366.
- Sherman A B, Clode A B, Gilger B C. Impact of Fungal Species Cultured on Outcome in Horses With Fungal Keratitis. Veterinary Ophthalmology 20, no. 2 (2017): 140–146.
- Ledbetter E C, Patten V H, Scarlett J M, Vermeylen F M. In Vitro Susceptibility Patterns of Fungi Associated With Keratomycosis in Horses of the Northeastern United States: 68 Cases (1987‐2006). Journal of the American Veterinary Medical Association 231, no. 7 (2007): 1086–1091.
- Jin Y, Zhang T, Samaranayake Y H, Fang H H, Yip H K, Samaranayake L P. The Use of New Probes and Stains for Improved Assessment of Cell Viability and Extracellular Polymeric Substances in Biofilms. Mycopathologia 159, no. 3 (2005): 353–360.
- Gao Y, Mai B, Wang A. Antimicrobial Properties of a New Type of Photosensitizer Derived From Phthalocyanine Against Planktonic and Biofilm Forms of nnn. Photodiagnosis and Photodynamic Therapy 21 (2018): 316–326.
- Clode A B, Davis J L, Salmon J, Michau T M, Gilger B C. Evaluation of Concentration of Voriconazole in Aqueous Humor After Topical and Oral Administration in Horses. American Journal of Veterinary Research 67, no. 2 (2006): 296–301.
- Nautscher N, Bauer A, Steffl M, Amselgruber W M. Comparative Morphological Evaluation of Domestic Animal Cornea. Veterinary Ophthalmology 19, no. 4 (2016): 297–304.
- Dugan S J, Curtis C R, Roberts S M, Severin G A. Epidemiologic Study of Ocular/Adnexal Squamous Cell Carcinoma in Horses. Journal of the American Veterinary Medical Association 198, no. 2 (1991): 251.
- Xu Y, Shrestha N, Préat V, Beloqui A. An Overview of In Vitro, Ex Vivo and In Vivo Models for Studying the Transport of Drugs Across Intestinal Barriers. Advanced Drug Delivery Reviews 175 (2021): 113795.
- Brand A. Hyphal Growth in Human Fungal Pathogens and Its Role in Virulence. International Journal of Microbiology 2012 (2012): 517529.
Citations
This article has been cited 0 times.Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
