Known by many names including Pythosis, Phycomycosis, Florida Leeches, Gulf Coast Fungus, Swamp Cancer, disease caused by Pythium insidiosum is bad news. Pythiosis is caused by the aquatic fungus, Pythium insidiosum and is common in the tropical to subtropical areas of the Gulf Coast region of the United States, South America, and Australia. It normally infects aquatic vegetation and organic debris. Wounds in horses, dogs, or humans, contaminated by water with this organism allows entry of this organism and once started invades surrounding healthy tissue. Recent advances have significantly improived the prognosis of this disease. This article discusses clinical course, diagnosis, treatment, and prognosis of this terrible disease.

Damaged animal tissue is chemotactic for the organism and most probably the fungus gains entrance into animal tissue via wounds in prolonged contact with contaminated water. Typically, ventral body areas, including legs, abdomen, and chest, are affected. Wire cuts, puncture wounds, and ventral midline dermatitis caused by horn flies or Culicoides gnats are prime locations but lesions arising in areas where no wound was noticed occur.

Frequently the first signs are a nonhealing injury followed by a worsening characterized by increasing ulceration and a purulent discharge. Tumors composed of granulomatous masses form under the skin. These masses are very itchy and there is often trauma from biting or scratching. The discharge often contains a classic hallmark of this disease, "kunkers," which are hard, gritty, white to yellow masses that develop in tissue tracts. These granules branch macroscopically, which distinguishes them from granules seen in other skin diseases. Kunkers are composed of fungal hyphae, host exudate, and protein. Lameness, enlarged regional lymph nodes, anemia, and hypoproteinemia are other common findings. Occasionally, the disease may become systemic.

Note well: This disease is not a known zoonosis, but, protective latex gloves should be worn when examining patients followed by careful cleaning of exposed skin and careful disposal of contaminated surfaces.