Pythiosis in Horses by a Vet – 2025 Swamp Cancer Diagnosis & Treatment Update 🐴🌾
In this article
Pythiosis in Horses by a Vet – 2025 Swamp Cancer Diagnosis & Treatment Update 🐴🌾
By Dr Duncan Houston, BVSc
Introduction
Pythiosis, also known as phycomycosis or swamp cancer, is an aggressive, potentially life-threatening skin infection in horses. It primarily affects animals that graze in warm, wet climates—especially those in the Gulf Coast region. In 2025, awareness, early diagnosis, and advanced vaccine support give veterinarians and owners more tools to manage this challenging disease.
What Causes Pythiosis? 🦠
- Caused by Pythium insidiosum, a fungus-like organism (not a true fungus)
- Found in stagnant water and wet grass
- Enters through small wounds or scrapes on the skin
Where & When Is It Found? 📍
- Common in Gulf Coast states like Texas, Louisiana, Florida, Mississippi
- Seen mostly from late summer to early winter (August–December)
- Horses that stand or graze in flooded pastures or swampy areas are at highest risk
Clinical Signs & Appearance ⚠️
- Rapidly enlarging skin lesion, often on legs or underbelly
- Thick discharge of pus and blood
- Lesions have firm, gritty cores called “kunkers”
- Severe itching and self-trauma common
- Lesions may resemble other infections or tumors—diagnosis is essential
Diagnosis 🧪
- Biopsy and microscopic examination of tissue
- Histopathology and PCR for definitive diagnosis
- Pythium does not grow well in standard culture, and antifungal response is poor
Why Antifungals Fail ❌
- Pythium is not a true fungus—so antifungal medications often don’t work
- It is classified as an oomycete, a plant-like organism more related to algae
Treatment in 2025 💊✂️
1. Early Surgical Removal
- Primary treatment in early-stage cases
- Lesion must be removed with wide margins to reduce recurrence
- Lesions in difficult locations may not be operable
2. Vaccination
- Vaccine by Pan American Veterinary Labs (Hutto, Texas)
- Most effective in early cases
- Has shown partial success even in chronic infections
- Administered as a series of injections with veterinary supervision
3. Supportive Care
- Wound cleaning and bandaging
- Pain management and anti-inflammatories
- Monitoring for recurrence or spread
Prognosis 🩺
- Better if diagnosed and treated early
- Advanced or inoperable cases may require euthanasia
- Vaccine offers hope for cases that cannot be fully excised
Case Example: Texas Gelding with Early Pythiosis
- A 7-year-old gelding developed a fast-growing lesion near his hock
- Lesion was draining pus and developed hard granules
- Biopsy confirmed pythiosis; lesion was surgically removed
- Horse received vaccine series and healed completely
- No recurrence after 6-month follow-up
FAQs About Pythiosis in Horses
Q: Can horses spread pythiosis to each other?
A: No—this is an environmental disease, not contagious between horses.
Q: Is the vaccine a cure?
A: No, but it may improve the immune response and help prevent recurrence, especially after surgery.
Q: What if I can’t afford surgery?
A: Talk to your vet about the vaccine and supportive management. Early lesions may respond better than chronic ones.
Conclusion
Pythiosis is an aggressive skin disease that thrives in warm, wet environments—especially where horses graze near stagnant water. In 2025, the best defense is early detection, surgical removal, and supportive care with the pythiosis vaccine. If your horse develops a wound that doesn’t heal or oozes thick, foul-smelling discharge, call your vet immediately. The sooner pythiosis is diagnosed, the better your horse’s chances of survival.
Need help diagnosing or treating a suspected case of pythiosis? Visit AskAVet.com or download our app 📱 to consult with Dr Duncan Houston for diagnostic support and treatment planning. 🩺🐴
