Mites are small arthropods belonging to the class Arachnida and the subclass Acari (also known as Acarina).
Most mites are tiny, less than 1 mm (0.04 in) in length, and have a simple, unsegmented body plan.
Some species live in water, many live in soil as decomposers, others live on plants, sometimes creating galls, while others again are predators or parasites.
This last group includes the commercially important Varroa mites of honey bees, and the scabies mite of humans. (source)
So can guinea pigs die from mites?
Mange mites are those that are found because of exposure to other infected animals.
The mites move quickly from one infected animal to another.
Exposure rates are high amongst animal shelters, animal parks, groomers and veterinary clinics.
The exposure to mange mites usually occurs between two to six weeks before the first symptoms are displayed of mange mites. (source)
Yes mange mites can possibly kill a guinea pig.
How mange mites do this is to burrow underneath the skin and then cause excruciating pain for the guinea pig, even worse than fleas.
As a result, they can suffer hair loss, scratching, and possible seizures.
As a result, this can be fatal to a guinea pig.
Mange mites can be treated, however this must be done as soon as possible so as to limit the spread.
It is best to seek the advice of a guinea pig friendly veterinary surgeon to treat them.