Re: Is this soil fungus/disease dangerous??
This is actually part of the intricate workings of the food chain down at its lowest level, where the appropriate fungi emerge to try to break down whatever debris is around.
You can read more about it — plus link off to some really expert sites — in this post of mine from the blog.
As far as the dog, I think you should look at the expert sites to try to find that out, or ask your vet if there is concern. But start w/the story above.