Pythiosis,sometimescalled Water Mold Infection or Swamp Cancer,is a fungal infection caused by an organism called Pythium insidiosum It is characterized by gastrointestinalsigns and/or dermatological signs and can be life threatening It is contracted when a dog swims in contaminated water and/or drinks contaminated water and not only effects dogs Cats, horses, cows, and even people can succumb to Pythiosis as well The most common sign seen in dogs that contract Pythiosis is extreme weight loss. This is usually is due to vomiting and diarrhea that is also caused by the disease process.Pythiosis can also effect the skin, though, causing ulcerative, draining lumpss and fistulas that never seem to completely heal. These are typically located on the legs, abdomen, chest, face, and/or tail. Depending on the degree of inflammation associated with the nodules, the areas may either be a bit spongy feeling or quite firm to the touch Many cases of Pythiosis don't ever develop clinical signs until the dog has been infected for a long time. This makes it difficult to diagnose based solely on a patient history of recently swimming in a pond. An intestinal biopsy will definitively show the presence of P. insidiosum. The genera Pythium as whole is difficut to culture as it doesnt grow very well on the routine fungal culture media and bacterial contamination that can skew results i common. Antifungals can be used, but less than 10 percent of cases fully recover from medications alone. The only truly curative measure that can be taken is complete surgical removal of any and all infected tissue. For skin lesions, this may involve a limb amputation. Any gastrointestinal involvement gets even trickier. Your vet may try removing pieces of intestine that are infected, but the prognosis is much graver if there is GI involvement.There are also specialized blood tests that can check for the presence of the organism .