I realize that it will be harder for you to look over this adult wild that you bring into the house to see if it has any pests. Here's one idea, a guy who works with squirrels told me this:
Begin quote---[[Not sure of the ages, but we give all our squirrels entering our facility a flea bath in Dawn dish washing liquid, submerging them up to their neck in the wash, and then a rinse. This can be a daunting task if they are older and stronger and more wiry. Right after we take them out of the bath we dab the head with a cotton ball whetted with kitten flea spray to kill any that escaped to the head.
For older squirrels, we fill the tub deep enough to where they can't get their feet under them to jump out, put a cup of vinegar in the water, dab their head with flea spray, and let them swim for a few minutes, ( they're good swimmers.) Use a Nit comb on them after the bath to remove dead flea.
For natural control of fleas in carpeting, ( treating the source,) sprinkle the carpet with diatomaceous earth. It is made from the ground up bodies of ancient Diatoms that died thousands of years ago and are mined in ancient sea beds. Microscopically, the powder looks like tiny razor blades, which is the secret to killing fleas. Fleas have an exoskeleton. When they get diatomaceous earth on their exoskeleton, it makes tiny cuts in it, and they start to leak body fluids. They die of dehydration. No chemicals, you just wait a few days and vacuum the powder and dead fleas out of your carpet.
Bill
PS. Make sure your Vacuum has a really good filter, otherwise it creates a cloud of Diatomaceous dust! ]] End quote---
I also wonder if you could eat Brewers Yeast yourself? Fleas are not supposed to like it, and may avoid you if your skin tastes of it. Anyone prone to yeast infections might not want to eat it. I'm not an expert on this, just offering thoughts.
Using diatomaceous earth would help keep ahead of and or prevent if that would give you peace of mind. I think it might be important to get the food grade one, so that it is not toxic to animals; other than the bugs of course.
Thank you for your kind words about my squirrel habitat. I had so much fun creating it. :-)