Ocular Disease in Horses: Omegas May HelpBy Kentucky Equine Research Staff · May 31, 2017
The surface of the horse’s eye and inner lining of the eyelid harbor a microbial population that includes various species of bacteria and fungi. Under normal conditions, these microbes play a role in maintaining a healthy ocular environment, though other times they can actually contribute to diseases such as keratomycosis.
Keratomycosis, also called fungal keratitis, refers to an inflammation of the eye surface, known as the cornea, due to the presence of fungi. This condition is somewhat common in horses, and if not diagnosed and treated in a timely fashion, can result in the loss of vision or even the eye itself. Unfortunately, even swift intervention may not be successful in all cases. According to a recent study*, one potential reason for treatment failures is the presence of fungal biofilms.
“Biofilms are defined as well-structured microbial communities that adhere to a surface [in this case, the cornea] and embed in an extracellular polymeric matrix,” wrote the researchers.
They went on to explain the advantages of living within a biofilm, such as protection against the environment and physical and chemical stresses (e.g., the horse’s tears contain enzymes that can potentially harm or kill them) and even resistance against antifungal agents such as itraconazole and amphotericin B.
Not all fungi produce biofilms, but infections become more difficult to treat if they do.
Fungi are commonly found in horse environments, and an estimated 20% of horses have fungi as part of the natural ocular flora. Just like the microbiomes on the skin and in the gastrointestinal tract, any changes in the ocular microbiome due to injury or concurrent disease can result in infection. Ensuring the overall health of the horse through appropriate management and nutrition, examining each horse daily if possible, and treating infections quickly will help improve treatment success.
“Another way to keep eyes healthy is through dietary supplementation with omega-3 fatty acids. Not only do omega-3 fatty acids play a role in eye development in young animals but also help manage certain eye diseases. Plus, omega-3 fatty acids have natural anti-inflammatory properties,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research (KER).
KER’s EO•3 contains the marine-derived fish oils DHA and EPA, and is designed to be top-dressed on feed.
*Brilhante, R.S.N., P.V. Bittencourt, D. de Souza Collares Castelo-Branco, et al. Biofilms of Candida spp. from the ocular conjunctiva of horses with reduced azole susceptibility: a complicating factor for the treatment of keratomycosis? Veterinary Ophthalmology. In press.