Horse Owner Alert: Pythiosis

Pythiosis in Florida

We often experience horses being admitted to the UF Large Animal Hospital with a diagnosis of cutaneous pythiosis, an infectious disease caused by the pathogen Pythium insidiosum, which leads to granulating skin lesions. The pathogen thrives in swamps or marshes but can live in any body of water that does not freeze. However, pythiosis can develop despite good management and housing.

The most common place for a lesion to occur is on the lower limb, but horses can develop lesions in other places on the body. Any area on the horse that is exposed to Pythium insidiosum can develop pythiosis.

WARNING: These photos contain imagery that may be considered graphic in nature and may not be suitable for all audiences. Click to view before and after pythiosis photos.

How do horses get pythiosis?

  • Drinking water with Pythium insidiosum in it
  • When the pathogen enters a wound that is submerged in water that contains Pythium insidiosum

What does this mean for Florida horse owners?

Florida’s marshy environment, in addition to its natural disasters like hurricanes and floods, leads to standing water which makes it a prime area for horses to get pythiosis. Florida horse owners are encouraged to remove standing water from pastures, move horses to a different location, or fence off ponds or other bodies of standing water to prevent horses from becoming infected with Pythium insidiosum. This becomes especially important now with hurricane season nearly upon us.

Early detection and prompt veterinary referral to a facility that can treat pythiosis is extremely important for the best outcome. If you have any questions or suspect that your horse may have pythiosis, contact your veterinarian or contact the UF Large Animal Hospital at 352-392-2229.

University of Florida


As part of both the Institute of Food and Agricultural Sciences and UF Health, Veterinary Medicine is dedicated to advancing animal, human and environmental health through teaching, research, extension and patient care.

IFAS footerblock

University of Florida

Animal Hospitals

Need animal care? Visit the UF Small Animal and Large Animal Hospitals. From dogs, cats, birds and exotics to horses, cattle, llamas, pigs and many other large farm or food animals, our experienced veterinary staff is ready to assist.


Syndicated Podcast

Animal Airwaves

Animal Airwaves is a daily radio series that features one-minute segments relating to animal health, ranging from insights into animal behavior to veterinary patient care breakthroughs and trends.