New research warns dog parents to keep their paws out of warm ponds and lakes due to a haunting disease known as “swamp cancer,” or pythiosis. It’s not actually cancer, but a parasitic fungus found in warm lakes and ponds that causes deadly skin sores. Scientists at the University of Florida have recently been digging it up all throughout Florida and issued a warning to keep furry friends out of warm bodies of water.

What is pythiosis?

Pythiosis is also known as equine pythiosis, “Florida horse leeches,” “summer sores” or bursautee, and is thought to be caused by Pythium insidiosum or Lagenidium, unusual mold- and fungus-like organisms that aren’t technically a mold or fungus. The scientists found 11 of 19 lakes or ponds sampled in North Florida and 25 of 25 in Central Florida contained the ghastly pathogen.

The main U.S. laboratory tracking this disease, Pan American Veterinary Labs led by Dr. Bob Glass, agrees with this published research. Glass reports that a decade ago his lab identified fewer than ten cases a year in dogs. He now says they diagnose about 20 canines a month with pythiosis. Yikes! Glass blames global warming on the surge of this tropical disease. He estimates 60% of cases come from Florida, 25% from Texas and 10% from Georgia, Louisiana, Mississippi and Alabama combined.


Pythiosis usually begins after an animal has been exposed to stagnate, warm water. Pet parents often notice a small irritated area on the legs, stomach or other exposed area within a day or two of contact. The lesion is often mistaken as coming from a sting or bite, small puncture or otherwise insignificant injury.

Despite cleaning and topical antibiotics, the lesion grows and within a few days it is a red, sometimes bleeding mass. Most owners seek veterinary help at this stage. Sadly, these lesions are understandably misidentified as a snakebite, foreign body or infected deep puncture.

The lesion fails to respond to traditional antibiotics and continues growing, earning the moniker of “cancer.” Even if tissue samples are obtained for pathology, the report only reveals “inflammatory response” or “tissue necrosis.” So how do you test for pythiosis?


Pan American Veterinary Labs and Louisiana State University School of Veterinary Medicine have developed a specific test for pythiosis that can accelerate diagnosis in suspected cases. Some animals will develop a particularly devastating internal form that will cause fever, vomiting and diarrhea, weight loss and abdominal masses. If diagnosed early, treatment is available.


Pan American Veterinary Labs has developed an effective vaccine-like treatment for horses and humans. Unfortunately, this treatment does not appear to be as successful in dogs and other animals at this time.

Aggressive surgical removal of infected areas is the best treatment. Amputation is recommended in many cases. Internal or gastrointestinal forms of pythiosis require extensive surgery and carry a poor prognosis. Medical treatment with potent antibiotics and antifungal drugs may also be advised.

If you live in the southeastern United States, keep your pets out of still, warm waters and mushy marshes and swamps. Similar to the spread of West Nile virus and heartworm disease, we will continue to see a rise in tropical diseases such as pythiosis or “swamp cancer.” If you observe any skin lesions that don’t immediately improve, have your veterinarian examine your pet. Pythiosis progresses rapidly and hours could mean the difference between diagnosis and death.

Oct 26, 2015
Pet Health

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