Guinea pigs ALWAYS have mites, living on them in a dormant state....and then they become active (I guess you'd say?) esp. under stressful conditions.
They are VERY itchy for the poor pigs, who will scratch until their hair is gone, and then keep scratching themselves into bloody shreds. I have seen some horrible horrible pictures. Can you imagine what would have happened to poor little Sam if you hadn't rescued him, and gotten the care he needed?! Death by a wild animal would have been preferrable.
He's adorable, and I hope that he finds a loving home!
PS...their little chirping sounds are my FAVORITE thing about them!