The only contagious disease it discribed seems to be ringworm. And the on the animal skin it's not visible at all. So it shouldn't be ringworm. Is the info on that site complete?
I already did about a lump on it's belly. The vet said that it was a soft lump and it very loose and not a hard and fixed lump. Now there seems too be the additional stuff I mentioned.
My guinea pig has these little soft "pimples" and "stripes" under the skin of it's belly. They can't be seen but can be felt when you feel it with your hand. Are those fat deposits or are they tumors? Are they contagious?