Lice and mites are the most common external parasites of guinea pigs. Lice are tiny, wingless, flattened insects that live within the hair coat; both the adults and their eggs are found attached to individual hairs. A mite similar to the scabies mite of people causes serious infestations in pet guinea pig.
Two types of biting lice may affect guinea pigs. Both scratch the skin surface and feed off of body fluids that exude through the very superficial wounds they create.
Light infestations usually go unnoticed, but heavy infestations are usually accompanied with excessive itching, scratching and some hair loss, and scabs may also be evident on and around the ears. Your vet can confirm the diagnosis by direct examination of the hair coat.
Direct examination is usually all that is necessary, though use of a microscope is very helpful. Your vet will usually prescribe a spot on treatment, injections or a shampoo.
Lice can be transmitted by direct and intimate contact between infested and uninfected guinea pig. Therefore, pet guinea pigs are very unlikely to harbour these parasites unless they are recent acquisitions that were previously in contact with louse-infested guinea pigs.
Being placed in close contact with new infested guinea pigs could also infest established pet guinea pigs. Guinea pig lice do not parasitism people.
A mite similar to the scabies mite of people causes serious infestations in guinea pig. Mites are microscopic, spider-like organisms that live within the outer layers of the skin. They usually cause intense scratching and significant hair loss. Some cases without scratching have been reported. Some guinea pigs become very lethargic due to an infestation and will scratch until they cause open sores on their bodies. In severe cases, guinea pigs may run wildly or in circles, and occasionally even have convulsions.
Lice will probably be visible to the naked eye, but if your vet is unsure, they will examine your guinea pig using a hand lens or microscope to help visualise the lice. Your vet may also use some sticky tape to take a sample of hair to examine further under a microscope in the lab.
If mites are suspected, your vet will take a number of skin scrapings which they will examine under a microscope in the lab to confirm the diagnosis.
Successful treatment consists of 1-4 injections of an antiparasitic drug 10-14 days apart.
All housing should be disinfected and if your guinea pig travels on hay it is advisable to discard the hay and purchase a new or different supply.