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[MrBredli]

Does your flatmate have a license? If not, you know you could get into trouble simply because it is on the same premises as your animals?

The mites will eventually make there way to your snakes, no doubt about it.

I'm certain the snake will develop RI very soon if it hasn't already, check its belly, probably already has scale rot too.

If i were you i'd scrub the cage out for starters and buy some TOD. Definitely get it to a vet soon ASAP. As for your flatmate, kick him in the balls and give him a bill for your costs once you've tended to the snake's needs.