@ drache - from what I have read, the simple answer is YES, the parasite count is apparently lower in salamanders than it would be in wild fish or frogs. For what reasons, whether mere size of the animals, or habitat, I have no idea. Information about relative parasite load hasn't been jumping out at me.
That said, NO wild prey are parasite free. It comes down to what is a natural balance, ie: how many parasites would the snake(s) normally eat in the wild, and how many is the snake accustomed (and genetically/evolved to be capable) to accomodating.
It would make sense that a snake eating a diet of 100% frogs, would soon have a very unhealthy parasite load, moreso than it would encounter in the wild. Therefore, while a single frog once in a while is probably OK, I simply choose to avoid them from now on, as there are enough other food sources around that I have no need to risk frogs.
Maybe the TYPES of parasite in frogs, are of less concern than those found in salamanders as well. Ultimately, I figure, samalanders are a far more common and regular food source than frogs, so whatever parasites may be inside salamanders, the snake is probably more accustomed to them and/or immune to them.
On this subject, not sure if I mentioned it elsewhere, but my snakie is now eating fuzzy mice and she seems to have a grand time dragging and flopping the mouse all around her cage before finally deciding to chow down on it