Merck Manual

Please confirm that you are a health care professional

honeypot link
Pet Owner Version

Disorders and Diseases of Guinea Pigs


Katherine E. Quesenberry

, DVM, MPH, DABVP (Avian);

Thomas M. Donnelly

, BVSc, DVP, DACLAM, DABVP(ECM), The Kenneth S Warren Institute

Reviewed/Revised Nov 2019 | Modified Oct 2022
Topic Resources

Health problems among guinea pigs that live alone are usually related to aging, dental disease, reproductive disorders, injury, or improper care. Infectious diseases caused by certain viruses and bacteria usually occur only in guinea pigs that live with other guinea pigs. Intestinal parasites are not common. Tumors are rare in young guinea pigs but are more common in guinea pigs that are more than 5 years old. Treatment of infectious diseases can be complicated by the fact that guinea pigs are more sensitive to antibiotics than other types of pets.

Prevention of health problems in guinea pigs is key. A proper diet that does not change from day to day, clean water, bedding materials that are gentle on your pet’s skin, frequent cleaning and disinfecting of the cage, a low-stress environment, and sufficient exercise all help prevent illness.

Sickness causes guinea pigs to be stressed; if your pet is sick, hold it as little as possible. Antibiotics can cause problems in guinea pigs’ digestive tracts, so your pet may not tolerate these medications. Most disease treatments should include extra vitamin C. Diarrhea and other illnesses may cause your guinea pig to become dehydrated. Signs of dehydration include dry stools, dark urine, or skin “tenting” (skin that returns to its normal position slowly after being pinched). If your pet is dehydrated, your veterinarian may provide fluid treatment. Animals that will not eat may require a stomach tube.


Guinea pigs are very sensitive to the effects of many antibiotics. These toxic effects may occur directly as a result of the medication or because the antibiotic causes an imbalance in the bacteria that usually live in your pet’s intestines. Many antibiotics, including penicillin, ampicillin, lincomycin, clindamycin, vancomycin, erythromycin, tylosin, tetracycline, and chlortetracycline, can cause this problem. Antibiotic ointments used on the skin can also be toxic to guinea pigs. Guinea pigs that receive these antibiotics may develop diarrhea, loss of appetite, dehydration, or a drop in body temperature. Death can occur in less than a week if the antibiotic treatment continues. Inadequate nutrition and vitamin C deficiency can make your pet more likely to develop these problems. Even guinea pigs that do not show signs of problems with antibiotics may die suddenly. Your veterinarian can diagnose the toxic effects of antibiotics in your pet by examining the animal and testing its feces.

There is no effective treatment for this condition other than general support and stopping the antibiotics. In general, you should avoid giving your guinea pig any antibiotics unless specifically directed by a veterinarian familiar with these animals. If your guinea pig must take antibiotics, you will need to monitor its health carefully. If your pet develops diarrhea or stops eating during treatment, contact your veterinarian immediately.

Digestive Disorders

Digestive disorders in guinea pigs may be caused by infections or by an improper diet.


Many types of bacteria, viruses, and parasites can upset a guinea pig’s digestive system. Some signs that your pet’s digestive system is upset are diarrhea, weight loss, loss of energy, lack of appetite, and dehydration. Guinea pigs affected by these illnesses may die suddenly without seeming sick. Others may have a range of signs such as rough fur coat, fecal staining of the fur around the anal area, loose stools, hunched posture, dull eyes, dehydration, pain when the abdomen is touched, fever, or a low body temperature.

Increasing roughage (fiber in the diet) and decreasing grains and sugars may help treat diarrhea. One way to increase dietary fiber is to provide hay in addition to commercial guinea pig feed. Probiotics (supplements that contain live bacterial cultures) may help to restore the healthy balance of bacteria in the digestive tract. It is important that your pet drink enough water. If your guinea pig will not voluntarily drink sufficient water, your veterinarian may provide additional fluids by injection. Antibiotics should only be used when absolutely necessary because their use can worsen the imbalance of bacteria in the digestive tract. Follow the treatment program prescribed by your veterinarian carefully. Keeping your guinea pig’s bedding, water bottle, and housing clean and sanitized and promptly removing uneaten food can help prevent infection by reducing the level of disease-causing organisms.

Dental Disease

Teeth, guinea pig

Teeth, guinea pig

Guinea pigs drool whenever there is a problem with chewing or swallowing. This condition is sometimes referred to as slobbers. The cause is usually improperly aligned teeth (malocclusion). Malocclusion may be inherited or due to lack of vitamin C, injury, or imbalances of certain minerals in the diet. The teeth of guinea pigs grow continuously throughout the animal’s life. If the teeth or jaws do not meet properly, the teeth may become overgrown, making it difficult for the animal to chew. Dental disease can cause weight loss, bleeding from the mouth, or abscesses in the tooth roots that may lead to sinus infections. These kinds of problems are very common in guinea pigs.

If your pet is slobbering or drooling, your veterinarian will evaluate this problem carefully. The molars in the back of the mouth are often the cause of this problem, even though teeth in the front of the mouth may seem normal. Some teeth may need to be clipped or filed to help your pet’s jaw close properly. If the problem continues, monthly visits to your veterinarian for dental care may be necessary.

Eye and Ear Disorders

Signs of conjunctivitis (pink eye) include watering, crusting, and redness of the eyes. In guinea pigs, conjunctivitis is usually caused by infection by bacteria, such as Bordetella or Streptococcus species, that cause general upper respiratory disease ( see Lung and Airway Disorders Lung and Airway Disorders Health problems among guinea pigs that live alone are usually related to aging, dental disease, reproductive disorders, injury, or improper care. Infectious diseases caused by certain viruses... read more , below). Treatment may include antibiotics. As always with guinea pigs, carefully watch your pet’s reactions to the medication.

Ear infections are rare in guinea pigs. When they do occur, they are usually the result of bacterial infection. They may occur at the same time as pneumonia or other respiratory disease. Signs of infection may include discharge from the ears, but sometimes there are no signs of infection. In severe cases, the animal may become deaf. If the infection spreads from the middle ear to the inner ear, your pet may show nervous system problems such as imbalance, head tilt, walking in circles, or rolling on the ground. Treatment depends on whether the infection is in the outer ear canal, middle ear, or inner ear.

Nutritional Disorders

The most common nutritional disorder in guinea pigs is a lack of vitamin C. Loss of appetite also occurs and is usually a sign of another problem such as disease or problems with the teeth.

Vitamin C Deficiency (Scurvy)

Like people, apes, and monkeys, guinea pigs cannot produce their own vitamin C. If they do not get enough of this vitamin in their diet, their bodies’ supply of vitamin C disappears quickly. Vitamin C is required for the production of collagen, a protein necessary for healthy skin, joints, and blood vessels. Reduced collagen can cause problems walking, swollen joints, and bleeding under the skin, in the muscles, in the membranes around the skull, in the brain, and in the intestines. Guinea pigs with vitamin C deficiency may be weak, lack energy, and walk with a limp. They may have a rough hair coat, lose their appetite, lose weight, have diarrhea, become ill, or die suddenly. Your veterinarian can diagnose vitamin C deficiency by investigating the diet and by examining your pet, looking especially for bleeding or joint problems.

Some Fruits and Vegetables with High Vitamin C Content

  • Green (bell) peppers

  • Oranges

  • Strawberries

  • Broccoli

  • Parsley

  • Red cabbage

  • Turnip greens

  • Kale

Vitamin C added to fortified guinea pig diets is not very stable and breaks down with exposure to moisture, heat, and light. Fortified diets may lose half of their vitamin C content within 3 months of manufacture. Guinea pigs may also develop vitamin C deficiency even if the dietary level of vitamin C is appropriate. This can happen if they have other illnesses or problems that prevent them from eating enough or that prevent their bodies from absorbing vitamin C properly. Treatment includes giving your pet vitamin C daily, either by mouth (as directed by your veterinarian) or by injection at your veterinarian’s office. Guinea pigs need at least 10 mg of vitamin C per kilogram of body weight daily (pregnant females need 30 mg/kg daily). Multivitamins are not recommended because some of the other included vitamins could be dangerous for guinea pigs.

Appetite Loss

Loss of appetite can happen for many reasons, including disease, recovery from surgery, exposure to drafts, lack of fresh water, not being able to chew properly because of an underbite or overbite, and a condition called ketosis, in which your pet’s body produces too much of one of the byproducts of digestion. Changes in the type of feed or water or in the bowl or bottle that your pet eats or drinks from may also trigger loss of appetite. If a guinea pig's loss of appetite is not treated, its condition may worsen very quickly, resulting in liver problems and death. Ketosis, which may be irreversible, can develop even in guinea pigs that begin to eat again. Your veterinarian will determine appropriate treatment. Guinea pigs that refuse to eat may need to be carefully fed by syringe with a soft diet (a commercial critical care diet, vegetable baby food, or a pureed pelleted diet).

Metabolic Disorders

The most common metabolic disorders in guinea pigs involve abnormal metabolism of the mineral calcium.

Hardening of the Organs (Metastatic Calcification)

Guinea pigs that suffer from metastatic calcification (hardening of body tissues caused by calcium deposits) often die suddenly without any signs of illness. This condition usually occurs in male guinea pigs that are more than 1 year old. Signs, if they are seen at all, can include weight loss, muscle or joint stiffness, and increased urination (because of kidney failure). The cause of this condition is uncertain but is probably related to diets that contain too much calcium, phosphorus, or vitamin D and not enough magnesium. Most high-quality commercial guinea pig feed is formulated to contain the correct amounts of these nutrients. Check the nutrition information on the package label before buying pellets for your guinea pig, and do not give additional vitamin or mineral supplements.

Pregnancy Toxemia (Ketosis)

Ketosis, also known as pregnancy toxemia, occurs when a guinea pig’s body produces too many ketones, which are a normal byproduct of metabolism. There are many causes of pregnancy toxemia in guinea pigs. These include obesity, large litter size, loss of appetite during the late stages of pregnancy, insufficient exercise, environmental stress, and underdeveloped blood vessels in the uterus (an inherited condition). This condition usually occurs in the last 2 to 3 weeks of pregnancy or in the first week after birth. It most commonly affects guinea pigs that are pregnant with their first or second litters.

Although ketosis occurs most often in pregnant guinea pigs, it can also happen in obese guinea pigs (male or female). A guinea pig may die suddenly of ketosis without ever demonstrating signs of illness. In other cases, a sick guinea pig has worsening signs that can include loss of energy, lack of appetite, lack of desire to drink, muscle spasms, lack of coordination or clumsiness, coma, and death within 5 days. Ketosis may cause fetal guinea pigs to die in the uterus.

Your veterinarian can diagnose ketosis with blood tests and may also be able to identify fatty liver (caused by abnormal metabolism of fat) and bleeding or cell death in the uterus or placenta. Treatment, which is not usually successful in guinea pigs with advanced disease, can include glucose injections at the animal hospital, propylene glycol by mouth, nutritional supplements, and (for pregnant animals) emergency cesarean delivery. To prevent ketosis, make sure your pet eats a high-quality food throughout pregnancy, but limit the amount of food you give your pet to prevent obesity. Preventing exposure to stress in the last few weeks of pregnancy may also help.

Lung and Airway Disorders

Respiratory diseases in guinea pigs can quickly become serious. If you notice that your guinea pig is having difficulty breathing, see your veterinarian as soon as possible.


Pneumonia, or inflammation of the lungs, is a frequent cause of death in guinea pigs. Pneumonia in guinea pigs is usually caused by bacterial infection (most often Bordetella bronchiseptica, but other bacteria such as Streptococcus pneumoniae or Streptococcus zooepidemicus may also be the cause). In rare cases, it may be caused by a type of virus known as adenovirus. All of these infectious agents can cause illness without leading to pneumonia (see below).

Signs of pneumonia include oozing or discharge from the nose, sneezing, and difficulty breathing. In addition, guinea pigs with pneumonia may have conjunctivitis (pink eye), fever, weight loss, depression, or loss of appetite. Sudden death can occur when outbreaks occur among groups of guinea pigs. Your veterinarian can diagnose pneumonia from an examination or from tests of discharge from the eyes or nose. X-ray images may also show evidence of pneumonia in the lungs.

Treatment for pneumonia can include fluids (to ward off dehydration), syringe feeding if necessary, oxygen therapy to help with breathing, and vitamin C. If the pneumonia is caused by bacterial infection, your veterinarian will likely prescribe antibiotics. Although they can be toxic in guinea pigs ( see Antibiotics Antibiotics Health problems among guinea pigs that live alone are usually related to aging, dental disease, reproductive disorders, injury, or improper care. Infectious diseases caused by certain viruses... read more , above), certain antibiotics are safer than others, and your veterinarian may select one of these if needed. The antibiotic may be compounded into a suspension given by mouth, which should then be given as directed. Watch any guinea pig receiving antibiotic treatment carefully. If the antibiotic causes diarrhea, the treatment should be stopped immediately and your veterinarian contacted. If you have more than 1 guinea pig, preventing and controlling outbreaks of pneumonia require keeping your pets and their cages or tanks clean at all times and removing guinea pigs that are sick from the company of the others.

Bordetella bronchiseptica Infection

Guinea pigs without signs of illness may carry Bordetella bronchiseptica bacteria in the nose or throat. Sometimes groups of guinea pigs experience an outbreak of infection, during which all get sick and die quickly. Infection can be transmitted from one guinea pig to another when droplets are sprayed into the air by sneezing or coughing. The genital form of the infection can also be transmitted by sexual contact. Other animals, such as dogs, cats, rabbits, and mice, may be infected with these bacteria without showing any signs of illness, so pet owners should avoid letting their guinea pigs come into contact with other animals.

Streptococcus pneumoniae Infection

Guinea pigs may carry Streptococcus pneumoniae bacteria without seeming sick. These bacteria can cause sudden illness in previously healthy guinea pigs when they become stressed or stop eating; this can lead to death. One guinea pig can infect another by direct contact or by sneezing or coughing. Signs of streptococcosis include difficulty breathing, wheezing, discharge from the nose, and coughing. Infection can also cause inflammation of the middle ear, which can lead to a head tilt. Antibiotics can be used to treat the infection and limit transmission to other guinea pigs, but guinea pigs that do not seem sick may still be infected.

Adenovirus Infection

A type of adenovirus is specific to guinea pigs. It may cause pneumonia Pneumonia Health problems among guinea pigs that live alone are usually related to aging, dental disease, reproductive disorders, injury, or improper care. Infectious diseases caused by certain viruses... read more , but many guinea pigs carry this virus without any signs of illness. Carriers can suddenly become sick as a result of stress or anesthesia. This occurs more often in guinea pigs that are young, old, or have immune systems that do not work properly. Guinea pigs do not usually die from this virus, but those that do die often die suddenly without seeming sick. Signs of illness are similar to those seen in other viral or bacterial infections and include breathing difficulties, discharge from the nose, and weight loss.

Reproductive Disorders

Common reproductive problems in guinea pigs involve the ovaries or mammary glands (breasts). A metabolic disorder associated with improper calcium levels may also occur during pregnancy.

Ovarian cysts are very common in female guinea pigs over 1 year of age. The cysts usually occur in both ovaries, but occasionally only one ovary is affected. Signs include hair loss over the abdomen, loss of appetite, and loss of energy. To confirm the diagnosis, your veterinarian may use ultrasonography or x-rays. The recommended treatment is surgical removal of the ovaries and uterus (spaying). If left untreated, the cysts may continue to grow and could potentially burst.

Bordetella bacteria can infect guinea pig genitals and can be spread by sexual contact. Infection can cause infertility, stillbirth, or sudden death of guinea pig fetuses in the uterus.

Dystocia (difficulty giving birth) is caused by the normal stiffening of the tough fibrous cartilage that joins the 2 pubic bones. Stiffening of this cartilage, the pubic symphysis, limits the spread of the pubic bones. If the symphysis has not been stretched by a previous birth, the female will be unable to deliver her offspring normally. Cesarean sections are very risky for guinea pigs and the survival rate for the mother is poor. The safest option is to prevent pregnancy altogether by housing male and female guinea pigs separately or by spaying and neutering them. Female guinea pigs that are used for breeding should be bred for the first time before they reach adulthood.

Skin Disorders

Skin problems in guinea pigs are often first noticed as patches of hair loss. Several underlying problems can lead to hair loss, including infestations of fur mites or lice, ringworm, or fighting between incompatible animals. Another skin problem, pododermatitis, affects the feet.

Fur Mites

Fur mites, guinea pig

Fur mites, guinea pig

Severe infestation by mites may cause hair loss or itching. Some types of mites cause no signs. Others cause hair loss but do not seem to affect the skin, and still others burrow into the skin and may cause intense itching, hair loss, and skin inflammation. This latter type of mite usually infects the inner thighs, shoulders, and neck. The skin underneath the affected fur may be dry or oily and thickened or crusty. In severely affected animals, the affected areas may become infected, which can cause the animals to lose weight, have low energy, or run around the cage. Left untreated, convulsions and death may result. Guinea pigs catch fur mites from other guinea pigs or from contaminated items such as bedding. Your veterinarian can diagnose this condition either by examining your pet’s fur or by looking at scrapings from your pet’s skin under a microscope. Mite infestations are treated with injections or topical medications. Infestations can be minimized or prevented by making sure that living quarters are clean and sanitary and by minimizing your pet’s stress levels.


Guinea pigs that are infested with lice do not usually have signs, but in severe cases lice can cause itching, hair loss, and inflammation of the skin around the neck and ears. You can see the lice by looking at a piece of your pet’s hair under a magnifying glass. Treatment is usually with topical medication. To prevent this condition, keep the guinea pig’s cage clean.


Fungal skin infection (ringworm) in guinea pigs is most often caused by Trichophyton mentagrophytes. This infection is contagious to people and animals directly or through contaminated objects like bedding. The primary sign of ringworm is the presence of bald, scaly patches, usually starting on the face (nose, around the eyes, and ears) and head. The bald patches may be flaky, crusty, or red. The disease may also spread to the back. Affected areas can become inflamed and more severely infected.

Your veterinarian can diagnose ringworm by culturing hair samples for fungal growth or (in some cases) by shining an ultraviolet light on affected skin. Ringworm usually goes away on its own in healthy guinea pigs. However, treatment speeds healing and reduces the chance the infection will spread to others. Treatment consists of several weeks of oral antifungal medication and sometimes also antifungal shampoos or rinses. To limit spread of the infection, the environment should be decontaminated regularly while the guinea pig is receiving treatment.

Ringworm is highly contagious to humans and other animals. If handling an infected guinea pig is necessary, you should wear disposable gloves or wash your hands thoroughly with soap and warm water after handling.

Hair Loss (Alopecia)

Hair loss in guinea pigs has a number of possible causes. Animals housed in groups may chew or tear their own or each other’s hair because of social conflicts or dominance of older animals over younger group members. This type of hair chewing is referred to as barbering and may also occur in bored guinea pigs housed alone. Alopecia caused by barbering tends to occur in patches, possibly with evidence of bite marks or skin inflammation underneath the fur. Barbering may be prevented by separating affected animals, minimizing stress, weaning baby guinea pigs from their mothers early, and feeding animals long-stemmed hay. Hair loss can also be caused by genetic problems or problems in metabolism (the body’s breakdown of food into energy); this is especially true in female guinea pigs that have been used for breeding. Young guinea pigs that are weaning from their mothers may have hair thinning as their coat changes to coarser adult fur.

Pododermatitis (Bumblefoot)

Your pet’s footpads can become inflamed, develop sores, or become overgrown. This footpad inflammation, or pododermatitis, is usually caused by Staphylococcus aureus bacteria that enter the footpads through cuts or scrapes. Factors that increase the risk of infection include obesity, wire or abrasive cage flooring, poor sanitation, and injury. Over time, pododermatitis (sometimes called bumblefoot ) can lead to serious complications such as swelling of the lymph nodes, arthritis, inflammation of the tendons, and buildup of a protein called amyloid in internal organs. Your veterinarian can diagnose this condition by examining your guinea pig and possibly performing laboratory tests. Treatment consists of housing the guinea pig in a smooth-floored cage with soft bedding, improving sanitation, and administering medical treatment depending on the severity of the condition. Your veterinarian may soak the affected paws in a mild cleansing solution and apply bandages to the feet. Some animals need antibiotics and pain medications. In some cases, the condition does not respond to therapy. Animals with severe pododermatitis may require amputation of the affected area to avoid more serious complications.

Disorders Affecting Multiple Body Systems

Some guinea pig diseases affect more than one body system. These are also known as multisystemic or generalized diseases.

Enlarged Lymph Nodes (“Lumps” or Lymphadenitis)

Lymph nodes are glands located throughout the body that help fight infection. The lymph nodes around the neck often become enlarged or inflamed in guinea pigs. The usual cause of this problem is a bacterial infection, most often with Streptococcus equi subsp. zooepidemicus. The infected lymph nodes may become swollen and filled with pus (abscesses), sometimes only on one side. The infection can spread and cause ear infection, head tilt, or inflammation of the sinuses or eyes.

Infection spreads between guinea pigs through bite wounds, cuts or scrapes in the skin or in the mouth, sneezing, coughing, or genital contact. Your veterinarian can diagnose this condition by examination and laboratory tests. Antibiotics can be used, but antibiotics alone may not eliminate the infection. Affected lymph nodes may need to be surgically removed. Abscesses can be surgically drained. To help prevent infection of the lymph nodes, avoid using harsh or irritating bedding or food. Overgrown teeth and jaws that do not close properly should be corrected. Infections of the respiratory tract should be treated. Your pet’s living quarters should be kept clean and sanitary, and sick animals should be housed away from other animals to prevent the spread of disease.

Salmonella Infection

Diseases that can be Spread from Guinea Pigs to People

  • Scabies

  • Ringworm

  • Salmonellosis

  • Campylobacteriosis

  • Yersiniosis

  • Streptococcosis

Although occurrences are rare, Salmonella bacteria can infect guinea pigs. Some signs of infection include inflammation of the eye, fever, lack of energy, poor appetite, rough hair coat, enlarged spleen and liver, and swollen lymph nodes in the neck. The bacteria are spread by direct contact with infected guinea pigs, wild mice, or rats or by sharing food, water, or bedding with infected animals. Fresh vegetables may also carry Salmonella. Because an animal that is treated may still continue to infect other animals even when it does not seem sick, treatment may not be recommended. Guinea pigs can spread Salmonella infection to humans by direct contact, so appropriate sanitation measures (such as wearing disposable gloves and washing hands thoroughly) should be taken when handling any sick guinea pig.

Yersinia Infection

Guinea pigs occasionally become infected with Yersinia pseudotuberculosis bacteria through contaminated food, bedding, or water. The bacteria can also enter a guinea pig’s body through cuts or scrapes in the skin or through inhalation. If a guinea pig becomes infected, the illness may take several courses: 1) infection may spread to the bloodstream and cause sudden death; 2) infected guinea pigs may lose weight, develop diarrhea, and die over the course of 3 to 4 weeks; 3) lymph nodes in the neck or shoulder may enlarge; or 4) your pet may be infected without seeming sick. Veterinarians diagnose this infection by laboratory tests and examination of the sick guinea pig. All guinea pigs that are infected with these bacteria or that have lived in close quarters with an infected guinea pig must be euthanized, and the living quarters must be thoroughly sanitized and disinfected.

Cancers and Tumors

Younger guinea pigs may develop skin tumors or leukemia (a cancer of the blood), but most types of cancer are not common in guinea pigs until they are 4 to 5 years old. Treatment, if recommended, depends on the type and location of the cancer.

Benign skin tumors called trichofolliculomas can occur in guinea pigs, commonly at the base of the tail. These can be removed surgically.

One-fourth of tumors in guinea pigs affect the reproductive tract. Most of these tumors are in the ovaries or uterus. Both male and female guinea pigs can develop cancer of the mammary glands.

Lymphosarcoma is a malignant cancer; it causes what is sometimes referred to as cavian leukemia. Signs may include a scruffy hair coat or enlarged lymph nodes, liver, or spleen. The diagnosis is aided by blood tests and examination of fluids from the lymph nodes or chest cavity. The outlook for survival is poor; most guinea pigs only live a few weeks after diagnosis.

For More Information

quiz link

Test your knowledge

Take a Quiz!