Blasto is not commonly transmitted from pet to person (not that it couldn't happen of course), but it IS possible to be infected from the same source as the pet. They say it's pretty endemic to certain areas, but there have been people here from all over the country; it's everywhere.
I think it's a good idea to start Sporanox to be safe, and hopefully you won't be needing it. The symptoms, however, do sound pretty classic. Dirtbike only had lung involvement w/skin lesions. She was treated for about 5-6 months with Itra and then tapered off. She's now a huge bouncing-happy hound, but we were lucky that it was caught fairly early. Treatment is not fun or easy, but it can be less expensive - our meds came from Pet Health Pharmacy in Arizona.
Keep him eating at all costs; we were afraid DB would starve to death while being treated, but she's been eating to make up for it. She needs a diet... or maybe I could get her some tusks and pass her off as a very tall spotted walrus. Whatever it is, we'll be thinking about you guys and hoping for the best. And if it is Blasto, we're all here to help as best we can.
Good luck-
jen
a couple of links:
http://www.peteducation.com/article.cfm?cls=2&cat=1557&articleid=401http://www.canismajor.com/dog/blstomyc.html