Order: Rodentia

Suborder: Hystrichomorpha

Family: Caviidae

Scientific name: Cavia porcellus


American or English (short-haired)

Abyssinian (coarse hair in whorls or rosettes)

Peruvian (long hair parted down back)

Teddy (coarse curly to kinky hair)

Silky (silky long hair swept back, not parted)


The optimum temperature should range from 65-85 F with humidity between 40 and 70%. Guinea pigs do well in groups, especially males and females. Males (boars) may fight when housed together. The male may be left in the cage with the females (sows) when giving birth. Housing should provide good ventilation and an enclosure with solid flooring. Wire bottom cages are only acceptable if there exists some solid flooring to separate feet from the wire bottom. This prevents sores from developing on the bottom of the feet, which is a potentially serious condition. Guinea pigs also like to hide, so providing a cardboard or wooden box with an open bottom and hole in the side is a simple way to provide security. These animals also require daily exercise. You may allow free range in a room with close supervision but be sure to provide access to the cage for occasional bathroom breaks.

Bedding should consist of newspaper on the bottom with some other kind of substrate on top to allow the guinea pig to burrow. Wood shavings are a good choice, but be sure to use pine and not cedar. The cage should be cleaned at least weekly with soap and water disinfected once to twice monthly with bleach and water in a 1:30 solution. Bedding may need to be changed more often than weekly to prevent ammonia buildup from nitrogenous waste (urine).

Ceramic dishes work well in the cage since they are heavy and less likely to tip over. Bottles are best for dispensing water, but guinea pigs have a tendency to spit into them and they often need to be scrubbed daily with a brush.


Guinea pigs, like primates, are unable to manufacture their own vitamin C. Pellets and vegetables are inadequate at providing the necessary quantity of this nutrient. It is recommended that 1 teaspoon of vitamin C be added to 12 oz. of water daily, as it loses up to 50% of its potency within 24 hours. In addition to this supplementation, broccoli and cauliflower are very high in vitamin C. Wild clover, dandelions, and grass are nutritious as well and fruits such as apples, pears, peaches, and strawberries can be fed as treats. Vitamin C is necessary for collagen formation and, without it, a guinea pig may present with a number of problems including hemorrhages (especially gums), malocclusion, joint swellings, and respiratory infections.

Growing guinea pigs require more protein and calcium vs. adults. Feeding high energy, high protein, and high calcium diets to adult guinea pigs can lead to obesity and a shortened life span. Ileus, a physiologic disorder in which the GI tract becomes less active, may be caused by low fiber diets. Hay is crucial in providing the fiber needed for the intestines to work properly. Obesity is a common problem among guinea pigs fed commercial diets and can lead to cardiovascular disease and fatty liver syndrome. Most commercial guinea pig pellets are 3-5% fat and contain a lot of corn, oats, and grains. Cavy Cuisine (made by Oxbow), on the other hand, is an excellent adult maintenance diet with 25-28% fiber. It also contains a stabilized form of vitamin C that has a shelf life of 6 months (vs. 3 months, as with other feeds). As stated earlier, hay is crucial in maintaining a healthy GI tract. In addition to Cavy Cuisine pellets (which are made partially from timothy hay), guinea pigs should ingest a large quantity of timothy hay as part of their daily diet. Alfalfa hay is undesirable, as it promotes obesity and predisposes cavies to urinary and bladder stones due to its high calcium content.


Male guinea pigs (boars) reach sexual maturity by 4 weeks of age and produce viable sperm by 11-17 weeks of age. Female guinea pigs (sows) undergo their first estrus cycle at 2-4 months of age. The entire cycle lasts 15-17 days. The time prior to estrus, called proestrus, lasts about 1½ days. During this time, the sow shows increased activity and mounting behavior. The fertile period, called estrus, lasts 1-18 hours with spontaneous ovulation occurring about 10 hours after onset of estrus. The first estrus after giving birth is the most fertile and is likely to yield the most offspring.

Breeding should occur before 6 months of age in females. At about 9 months of age, the pelvis fuses and there is increased risk of dystocia (complicated birth). Gestation is typically between 60 and 70 days. Parturition should take place within 10-30 minutes.

Litter size is generally 2-4. Baby guinea pigs are precocious, meaning they are born with a full coat, open eyes, and can run and eat solid food immediately. Despite this fact, there is only a 50% survival rate without nursing. Newborns need the first milk, called colostrums, to provide the necessary antibodies to fight disease. Weaning takes place at about 3 weeks of age. Orphans can be fed a substitute diet of mashed cucumber, grated apple, oat flakes, chopped bread and pureed carrots and broccoli.

Guinea pigs should be sexed and separated at weaning. Females have an externally opening urethra to the vulva and a Y-shaped vulvar opening. Males have a slit-like opening between the two halves of the scrotum. It is possible to palpate and evert the penis.


Murmurs, gurgles, grunts: Contentment, comfort, shared feelings

Squeals, squeaks: Warning, young's cry of loneliness, fear, pain, begging for food

Rattles, hisses, teeth clacking: Aggression, threatening, warning opponent

Medical Problems

In general, guinea pigs should be given a physical exam by a veterinarian twice yearly. Warning signs of potential illness include a decreased appetite, weight loss or gain, and naso-ocular discharge.

Reproductive problems

Pregnancy toxemia is a disorder of heavily pregnant sows in the last 2 weeks of gestation or first week post-partum. It is also seen in very obese sows. Clinical signs include acute death, anorexia, lethargy, and reluctance to move, in coordination, seizure, and coma. One may also see crusted eyes and nares as well as breathing difficulty. This disorder can lead to spontaneous abortion of fetuses. Causes of toxemia include hereditary factors, obesity, lack of exercise, or any stress, which leads to fasting. This disorder may be prevented by avoiding obesity, decreasing stress in late pregnancy, and avoiding fasting by providing easy access to food at all times.

Mastitis means infection of the mammary glands. Sows have 2 nipples in the inguinal region. Any severe swelling or abnormal discharge is indicative of infection and requires immediate attention and systemic antibiotics. Other nonspecific signs of mastitis are anorexia, lethargy, discomfort and fever.

Bacterial Diseases

Stress plays a critical role in the development of infection. This includes poor sanitation, overcrowding, poor temperature control and ventilation, and dietary deficiency (vitamin C).

Salmonellas is transmitted via unwashed, fecally contaminated greens. Conjunctival transmission is also possible. Clinical signs of disease are conjunctivitis, chronic wasting, emaciation, abortion and rarely diarrhea. Diagnosis may be obtained through fecal culture but the organism is difficult to isolate. Prevention is obtained by practicing good sanitation and washing all greens thoroughly.

Strep zooepidemicus refers to the type of bacteria which is the primary cause of abscessed cervical lymph nodes. Transmission is via oral abrasions, aerosol, bite wounds, genitals (females), and conjunctiva. Strep pneumoniae is found in the upper respiratory tract of 55% of normal guinea pigs and is thought to cause disease only when the animal is stressed (vitamin C deficiency, pregnancy, etc.). Clinical signs include anorexia, poor hair coat, nasal discharge, and difficulty breathing.

Yersinia pseudotuberculosis is shed in the feces of wild birds and rodents. Guinea pigs contract the disease from unwashed contaminated greens. There are three presentations of disease. The first is widespread infection and death in 1-2 days. The second is a chronic wasting disorder with severe weight loss, diarrhea, and death in 3-4 weeks. Lastly, the organism may cause a nonfatal lymphadenopathy of the head and neck. Cultures of heart blood and abscesses are used to make diagnosis.

Bordetella bronchiseptica is a normal respiratory inhabitant in rabbits, which is capable of causing disease in guinea pigs. Transmission is through aerosol or direct contact and clinical signs include acute death, pneumonia, abortion, and stillbirth. For these reasons, it is best not to house rabbits and guinea pigs together.

Viral Diseases

Lymphocytic choriomeningitis as a natural disease occurs in mice, cavies, chinchillas, canines, and primates. It can be transmitted from these animals to hamsters. The virus is shed in urine and saliva. Clinical disease results in decreased growth, reluctance to move and limb extension, photophobia, conjunctivitis and seizures. The disease has the capability of infecting humans via conjunctiva, inhalation, ingestion and wounds. Humans may show no signs of disease or exhibit flu-like symptoms or, in rare cases, meningitis.

Adenovirus pneumonia is a disease of decreased contagiousness and morbidity but increased mortality in outbreaks. Affected cavies may die acutely or present with ruffled fur, weight loss, hunched posture, nasal discharge or breathing difficulty.

Guinea pig inclusion conjunctivitis (chlamydiosis) causes conjunctivitis in guinea pigs 1-3 weeks old. They present with redness and crusting of the eyelid margins. Spontaneous elimination of the infection occurs within one month of onset.

Dermatologic Diseases

Cervical lymphadenitis or "lumps" refers to a nonpainful abscessation of the cervical lymph nodes. It is best to attempt removal of the entire abscess intact to prevent recurrence. If this is not feasible, however, the abscess should be lanced, drained and fluid cultured to identify the specific bacterial agent responsible and allow treatment with the appropriate antibiotics. Transmission of the organism causing "lumps" is via abrasions in the oral mucosa. Recovered animals are always carriers.

Staph pododermatitis refers to a bacterial infection of the feet, which causes abscesses and arthritis in some cases. Wire cages may cause or aggravate the condition.

Alopecia, or hair loss, is a normal finding during late pregnancy in sows and at weaning in piglets. Barberism may result from the addition of new guinea pigs, boredom, or stress. Forming social groups at a young age can diminish stress between animals.

Dermatophytosis (commonly known as ringworm) is often seen in guinea pigs. The most common type is Trichophyton mentagrophytes . Clinical signs of infection are patchy hair loss, broken hairs and scaling beginning around the head and spreading over the back. Diagnosis entails extraction of a few hairs and placing them in a special culture medium. Treatment of choice is the oral drug griseofulvin at 15 mg/kg/day for 1 month.

Guinea pigs frequently present with lice infestation. They are either intensely itchy or show no symptoms and are diagnosed on routine examination. Lice are large enough to visualize. Flea powders safe for cats are effective in treating lice in guinea pigs, as is injectable ivermectin.

Sarcoptic mange is an important disease in guinea pigs in that it has potential to cause a transient infection in humans. Again, as with lice, guinea pigs may be itchy or show no symptoms at all. The treatment of choice is ivermectin injections at 2-week intervals for a total of 2-3 treatments. Diagnosis via skin scrape may be difficult.

Gastrointestinal Diseases

Guinea pigs have open-rooted, continually growing teeth. Malocclusion of molars and premolars cause excessive salivation and anorexia. Many guinea pigs present with neither of these symptoms and exhibit only weight loss due to an inability to swallow food. Diagnosis is made by thorough oral examination. Treatment requires filing the teeth under general anesthesia.

Normally, guinea pigs have primarily gram-positive bacteria in their gastrointestinal tracts. Certain antibiotics such as the penicillin's allow gram-negative bacteria to proliferate, causing diarrhea, enterotoxemia, and death. Care should be taken when deciding how to treat a particular infection.

Three types of protozoal parasites have been isolated from the GI tracts of guinea pigs. Cryptosporidium wrairi infects the small intestines, causing weight loss and chronic enteritis but not always diarrhea. Eimeria caviae infects the colon and cecum, causing watery diarrhea with blood. Fecal exam may reveal oocytes, but these are passed only intermittently. Both of these organisms are treated with sulfamethazine. Balantidium cavaie is a normal inhabitant of the GI tract of cavies but can proliferate and cause disease secondary to bacterial diarrhea. It is also diagnosed by microscopic examination of cysts in the feces.

Pinworms are considered nonpathogenic in cavies. They cannot become re-infected by eating stool. Treatment is with piperazine or pyrantel pamoate.

Musculoskeletal Diseases

Guinea pigs frequently present with paralysis. Causes include vitamin C deficiency, arthritis, soft tissue mineralization, vitamin E deficiency, urinary calculi, and trauma/spinal cord injury. Vitamin E deficiency can also lead to a myopathy characterized by difficulty moving, depression, and conjunctivitis. Treatment requires vitamin E injections. Prevention requires supplementation of vitamin E daily.

Metastatic calcification is seen in cases of magnesium deficiency. This can be either an absolute deficiency or caused by high phosphorous levels which tend to decrease the absorption of magnesium. Clinical signs include poor growth, muscle stiffness, abnormal posture, bone deformities, abnormal dental growth, and calcification of muscles, GIT, and footpads. Diet recommendations are as follows: calcium of 0.9%; phosphorous of 0.4%; magnesium of 0.08%; and potassium of 1.4%.

Urinary Tract Diseases

Cystic/urethral calculi (bladder stones) are seen in cavies on increased calcium diets such as alfalfa hay. Treatment is surgical removal. It is important to check kidney values prior to surgery to rule out secondary kidney damage.


Cancer is relatively rare in guinea pigs. Trichofolliculoma is the most common skin tumor. It is a benign tumor. Other benign tumors found in guinea pigs are sebaceous adenomas and lipomas. Fibro-sarcomas are malignant tumors found with less frequency.

Approximately 1/3 of reported mammary tumors in guinea pigs are adeno-carcinomas. The remainder are benign masses. Lympho-sarcoma can be found in the neck, heart and kidney. Lymphoblastic leukemia has been reported in cavies 5-27 months of age. Clinical signs include enlargement of the cervical, inguinal, abdominal and mediastinal lymph nodes. A virus may have a role in this disease.