Sources: 1, 2, 3. How to make sure your guinea pig is healthy:
- The long haired guinea pig's nose, eyes, and ears should be clean and free of discharge.
- The coat of the long haired guinea pig should be full, thick, and soft. Pat it a few times to see if you can find any bald patches or irritated areas. A little ruffle from playing is normal.
- The fur should be free of parasites such as lice, which can cause serious harm for the long haired guinea pig.
- The long haired guinea pig should be plump, round, and firm.
- Long haired guinea pig should not be underweight nor overweight; both of these conditions are signs of health issues or possible future health issues. [ed. putting the locks in Goldilocks]
The white pig pictured is a Peruvian; Wikipedia says:
The Peruvian is the progenitor of all modern long haired breeds, being a Guinea pig with hair that grows long continuously all over its body, sometimes to an excess of 20 inches.