I had never heard of this until recently, we are dealing with this at the veterinary hospital I work at. Pythiosis is caused by pythium insidiosum , an aquatic organism, which is often fatal for dogs. All of the literature I am reading has this as a disease for dogs in tropical and sub tropical climates, but goes on to say this has been documented in Kentucky, Missouri, Virginia ,New Jersey, Southern Illinois and Indiana. The disease presents in a few ways,gastrointestinal, with severe thickening of the gastrointestinal tract vomiting ,weight loss, sporadic diarrhea, or cutaneous resulting in non healing wounds and a mass that can be hard or spongy. This dog ,a 2 year old lab we are treating presented with a spongy lump on his front leg. We took the mass off and it was sent off, and came back yesterday that this is what we are dealing with. Unfortunatly this dog may lose his leg, as often amputation is the only way to stop this nasy thing from spreading. I am just learning about this, so if anyone has dealt with this please share...this is very scary. This dog was swimming in a lake in Virginia shortly before this showed up on him, the owner said this is the only place she has taken them to swim.