Dr. Justine Hammond, DVM
This paper is not for diagnostic purposes but simply to make guinea pig owners aware of potential or common diseases in their pets. If you see any of the signs noted below, please contact us to determine a definitive diagnosis and appropriate treatment plan. It is strongly recommended that you maintain consistent healthy check-ups for your guinea pig to ensure a long and happy life for your pet.
Guinea pigs can carry lice, mites or fleas. Many times these animals were infected at birth and carry a very low-grade infection, which increases during times of stress
(change or new environment) and symptoms become more apparent during these times.
Guinea pigs may become itchy and subsequently suffer hair loss or skin abrasions from the itching. If the parasite infection and itchiness are intense enough, guinea pigs can suffer from seizures. More commonly the signs are not so severe to cause seizures but guinea pigs do tend to break their skin while itching and a secondary bacterial

infection occurs. Some lice and fleas may be large enough to be seen with the naked eye so inspect your guinea pig.
Hair loss and skin lesions can be due to other health problems like fungal skin infections
(dermatophytes), behavioural disorders/ fighting or some reproductive diseases.
Additionally, some infectious agents (fungal and a type of mite) can affect humans. Be sure to have consistent veterinary care for your pet, watch for signs of itching and wash your hands after playing with your pet to avoid transmission.
Pictured below are some examples or guinea pigs with severely flaky skin. This can be safely and effectively treated once diagnosed properly.

Bumblefoot (or foot sores) begin as red areas on the bottom of the feet and then progress to erupting as open sores.
Once the sores open, they can easily become infected.
Eventually, if not addressed, the underlying bone can become infected, which can lead to fractures and whole body infections
These sores often occur from overweight guinea pigs or vitamin C deficient pigs housed on inappropriate bedding. We recommend recycled newspaper bedding. Be sure not to house guinea pigs on wire mesh, wood, plastic or any other hard surface without bedding. We also discourage the use of wood shavings as bedding because they can cause small cuts to the feet and bacterial infection can begin.
Also, strong smelling wood shavings (like cedar) contain oils that predispose guinea pigs to respiratory disease. Keeping the cage clean will reduce the possibility for infection and foot sores as well. Clean the entire cage at least weekly and spot clean daily. We also recommend regular toenail trimming.
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Pictured here is recycled newspaper bedding
Be sure to offer a source of Vitamin C to keep your guinea pig’s skin healthy and strong.
We recommend adding a crushed up children’s chewable Vitamin C tablet to fresh food items. Also, be sure that pellets are made specifically for guinea pigs and are used within 30 days of opening the bag. These pellets have additional Vitamin C and the
Vitamin C is broken down about a month after the package is opened. This topic is discussed in the section on Scurvy in this article.
It is a good idea to occasionally check your guinea pigs feet for any signs of redness or open sores. If you note changes or problems, bring your pet to a vet for evaluation.
Vets classify respiratory disease as upper (nose, sinuses and trachea) and lower (lungs and bronchi) respiratory disease. Infection in the lungs is also called pneumonia. Both of these, upper and lower, can occur in guinea pigs. Sometimes the disease will begin as upper respiratory and progress to pneumonia. Frequently, as you may guess, disease is caused by a bacterial infection. Common bacteria that lead to respiratory disease in guinea pigs are Bordetella bronchiseptica and Streptococcus.
Signs of respiratory disease often begin with discharge from the nose or eyes and
decreased appetite. This can progress to difficulty breathing, especially if pneumonia is present. Keep in mind that there may be other explanations for these respiratory signs aside from infection such as heart disease and pain.
Guinea pigs should ideally not be housed with rabbits for a number of reasons, one of which is that rabbits can carry Bordetella and not show signs of illness. These bacteria can be transmitted to the guinea pig and can be fatal.
Guinea pigs can develop stones in their bladder or along the urinary tract. Stones can develop secondary to infection but may not; some may develop from a consolidation of normal cells and debris with in the urinary tract. Signs include inappetence, hunched
posture, straining to urinate, frequent urinations or blood-tinged urine and pain.
If a stone is sitting in the urinary tract but not blocking the normal flow of urine, it can cause pain and predispose the pig to an infection (if one is not already present).
However, if the guinea pig cannot urinate past the stone because it is acting like a cork in a wine bottle, this is a life-threatening situation that must be addressed immediately.
This is because the job of the urinary tract system is to excrete built up degradation products of metabolism and keeps electrolytes in the body in correct balance (like potassium and sodium). If these become too far outside of the range of normal, life

threatening cardiac problems occur. Please seek veterinary care immediately if you
are concerned that you guinea pig cannot urinate properly.
We do not recommend that spinach, broccoli or alfalfa hay * be fed to guinea pigs. These items are very high in calcium and necessitate excessive urinary excretion of calcium. It is believed that these items may predispose guinea pigs to bladder stones. Please see our care sheets for guinea pig diet suggestions and healthy guinea pig veggie sheet for a discussion of appropriate foods for your pig.
*- Alfalfa hay is acceptable as a portion of young guinea pigs’ diets up to 6 months of age.
Gastrointestinal stasis (or GI stasis for short) is characterized by a decreased or
absent appetite, decreased or absent stool production, small or dry stools and
lethargy. Stasis generally occurs secondarily to another issue but is serious and warrants immediate medical attention. Even 12- 24 hours of not eating can be fatal
to a guinea pig. Stress, illness, pain, dental problems, some medications or changes in diet can all cause GI stasis.
Stasis begins usually from refusal or inability to eat. This allows for gas build-up within the GI tract. Gas causes distention, pain and can impede the gut’s ability to perform peristalsis (the act of pushing the food through the gut). This situation quickly spirals out of control as the gas continues to build up, the gut works less and less and the gas is not expelled causing further pain and distention. If the situation is not resolved, the gut can rupture or become so large with gas that it impedes major blood vessels and can be fatal.
It is very common for guinea pigs to stop eating when they become ill and so we must address not only the primary illness also the GI stasis.
Many times, we see guinea pigs that are in GI stasis from dental issues or poor diets.
Guinea pigs have teeth that grow throughout their lifetime. It is not only the front teeth
(incisors) that grow but also the back molars. So while the front teeth may look normal, a guinea pig may have abnormal molars causing pain and causing the animal to not eat.
This is because, just like in humans, some guinea pigs have teeth that do not align properly in the mouth (and we don’t have braces for guinea pig teeth yet). In guinea pigs, normally aligned molars act to wear each other down during the act of chewing.

However if they are improperly aligned, portions of the tooth may continue to grow and have very sharp points that injure soft tissue in the mouth. This is why your veterinarian carefully inspects your guinea pig’s mouth during regular examinations. As an aside, I am often asked about giving wood or chew sticks to help with this situation.
The best (and really only) way for your guinea pig to wear his back teeth down is with his food (especially hay), as the chew toys or wood blocks only will come in contact with the front incisors and not the back teeth where the most common problems arise.
Pictured below are two examples of molar bridging. Guinea pigs can not eat when their teeth are this bad. This is a fatal situation left untreated. Even with treatment, the prognosis is guarded.
Pictured below is a guinea pig with incisor malocclusion and a missing incisor. This can be managed with monthly trimming.

Guinea pigs have a gastrointestinal system that is specifically designed to break down and utilize high fibrous foods with diluted energy levels, like grass hay. The good bacteria in the caecum (a sac-like projection from the intestines) are in balance in a healthy pig in order to break down these foods. Once a guinea pig is fed too much
“junk” food like foods that are high in sugar or simple carbohydrates, the bacterial balance in the gut is thrown off. The acidity in the caecum changes and allows for abnormal bacterial growth. Some of these bacteria produce high amounts of gases as they break down sugary foods. This is what sets the stage for GI stasis when poor diet is fed. Guinea pigs are so sensitive that too many pellets, fruits, yogurt drops or other treats can trigger this process. Please see our recommendations for proper guinea pig diets in order to avoid this situation.
Guinea pigs are one of the few mammals that need Vitamin C supplemented in their diets. The same is true for primates (yes, that means you!) and some types of bats.
These animals cannot produce their own Vitamin C and this must come from some food source in their diets.
If a guinea pig is deficient in Vitamin C we can see dental, feet and skin problems.
This can include difficulty healing from wounds or a propensity to get skin
wounds and foot sores. Guinea pigs that are Vitamin C deficient may also develop
diarrhoea and have a coarse fur coat.
A guinea pig requires fresh pellets made specifically for guinea pigs (because they have added Vitamin C). The Vitamin C becomes deactivated over time so we recommend that once a bag of pellets is opened, it should be used within 30 days and should be stored in an airtight container in a dark place. Vitamin C added to water becomes deactivated fairly quickly and we do not recommend supplementing in this manner. Instead, children’s chewable vitamin C tablets can be ground up and sprinkled on fresh foods daily. We recommend 100 mg daily of Vitamin C. Several small mammal food companies offer Vitamin C tablets as well.
For more information on the disease of scurvy and supplementation of guinea pigs, please see our Scurvy handout and guinea pig care sheet .
Ovarian cysts are very common in female guinea pigs (sows) around 2-4 years of age. These animals can have no symptoms at all or can exhibit decreased
appetite, fatigue, severe lethargy and
fur loss. Cystic ovaries are believed to predispose females to reproductive cancers. Pictured right is a female guinea pig growing her hair back after her spay.
Spaying is the best treatment for cystic ovaries which this girl had.

We sometimes see older guinea pigs with advanced heart disease. Most often when these animals come in ill, they have respiratory signs such as difficulty breathing.
Remember, the heart is pumping oxygen- rich blood to the body. When it has circulated, the blood returns to the heart depleted of oxygen and is sent to the lungs to acquire more oxygen. The blood, now full of oxygen, returns to the heart to be pumped throughout the body. When the heart muscle is not working optimally, a back up can occur in the lungs because the heart does not have the strength to push blood into the body (which takes a lot of energy and force). This can cause weakness, lethargy,
inappetence in the guinea pig and also what looks like respiratory disease but in actuality is a cardiac disease.
Pictured below is a radiograph of a guinea pig with an enlarged heart. An ultrasound of the heart is needed to further diagnose this disease.
Guinea pigs can get ear infections that affect either the outer portion, the middle canal or the inner portion of the ear. Signs of ear infection can range from scratching at the
ears, to head shaking to finally, a head tilt and difficulty balancing or walking.
The signs and severity depend on which portion of the ear is infected. The ear extends past the eardrum and into a portion within the skull. Many nerves run through this area as well as the apparatus that helps them to maintain balance. If there is infection and subsequent inflammation within this area, we see more severe signs like a head tilt, balance issues (the animal walks like a drunk human might) and eventually rolling.

Inner ear infections can occur either from an infection extending from the outer ear in or, more likely, extending from a sinus or dental infection and up into the skull. Of course, a head tilt (indicating some balance trouble) could be due to a number of diseases such as tumours, viruses, parasites migrating throughout the body or trauma.
If you note these signs, please seek medical attention for your guinea pig.