Disorders and Diseases of Hamsters

ByKatherine E. Quesenberry, DVM, MPH, DABVP (Avian);Thomas M. Donnelly, BVSc, DVP, DACLAM, DABVP(ECM), The Kenneth S Warren Institute
Reviewed/Revised Aug 2020

Adequate housing, a good diet, and routine preventive care will go a long way toward keeping your hamster safe, happy, and healthy.

Heart and Blood Vessel Disorders

Blood clots sometimes form inside one of the upper chambers of hamsters' hearts. This condition is called atrial thrombosis. The blockages are often found in the left side of the heart. Atrial thrombosis occurs in up to 70% of older Syrian hamsters.

Atrial thrombosis is usually the result of congestive heart failure, a condition in which the heart muscle weakens and cannot pump blood efficiently throughout the body ( see Heart Failure in Dogs). Both atrial thrombosis and congestive heart failure happen more frequently in older hamsters and are often connected with amyloidosis ( see Amyloidosis, below). Signs include rapid breathing, an irregular heartbeat, and a blue tint to the skin or gums. There is no effective treatment, but your veterinarian may be able to suggest ways of managing this condition for a time. Syrian hamsters with untreated congestive heart failure typically die within a week after signs begin.

Digestive Disorders

Diarrhea is one of the most common digestive system problems in hamsters and can be caused by several different disorders. Diarrhea in hamsters is sometimes called “wet tail.” Constipation is another common digestive problem in hamsters.


Proliferative ileitis, inflammation of the small intestine, is the most significant cause of diarrhea in hamster pups. The culprit is the bacteria Lawsonia intracellularis, which is most likely to infect hamsters that are stressed because of being transported, living in an overcrowded cage, surgery or illness, or changes in diet. The condition is more common in young hamsters than adults. Proliferative ileitis progresses rapidly, and many hamsters with this infection die. Common signs of this disease are wet or matted fur around the tail and belly, low energy levels, loss of appetite, and weight loss.

Diarrhea, hamster

Your veterinarian will likely make the diagnosis from the signs, history, and the animal’s response to treatment. Treatment includes fluid administration (either by mouth or by injection) to correct dehydration and possibly antibiotics. Sick hamsters should be kept separate from other hamsters to prevent spreading the illness, and the cages of both the sick and healthy animals should be thoroughly cleaned and sanitized.

Tyzzer disease, caused by the bacterium Clostridium piliforme, can have many of the same signs as proliferative ileitis. These include loss of appetite, dehydration, watery diarrhea, and sudden death. Hamsters contract this illness by eating feces that contain the bacteria. This illness is more common in hamsters that are young or stressed. Your veterinarian can diagnose this illness by examination or by doing laboratory tests. Blood tests are only sometimes accurate. Your veterinarian may treat your hamster with fluids and antibiotics. Hamsters that have this illness or that have been in close contact with sick hamsters should be kept separate from other hamsters to prevent spreading the disease. The bacteria can form spores and spread through the environment, so the cage, food containers, and water sources used by both sick and healthy animals must be thoroughly cleaned and sanitized.

Inflammation of the small intestines may be related to antibiotic use. Certain antibiotics with activity against gram-positive bacteria can be fatal for hamsters. Examples of these antibiotics are lincomycin, clindamycin, ampicillin, vancomycin, erythromycin, penicillin, and cephalosporins. These medicines can cause inflammation of the small intestine, resulting in diarrhea and death within 2 to 10 days. These antibiotics kill gram-positive bacteria that naturally occur in the intestines, allowing gram-negative bacteria to overgrow. Some types of gram-negative bacteria produce toxins that can cause serious illness. The cecum, a pouch at the end of the small intestines, becomes swollen with fluid, and the hamster develops diarrhea. Your veterinarian can diagnose this problem by finding out what medications your pet has taken recently and by performing laboratory tests. The bacterial overgrowth sometimes happens in hamsters that have not taken antibiotics. Once a hamster has this condition, the outlook is not good.

Salmonellosis, an inflammation of the intestines caused by Salmonella bacteria, is not common in hamsters. Signs of infection can include diarrhea, dehydration, weight loss, rough hair coat, and a swollen or bloated abdomen. Transmission of the bacteria occurs when the hamster’s food or bedding is contaminated by insects or wild rodents. Once a hamster is infected with Salmonella, treatment is not recommended. Salmonella infections can be transmitted to humans, even if the infected hamster does not seem sick.

The signs of illness when a hamster has an Escherichia coli infection are similar to other illnesses that cause diarrhea in hamsters. You veterinarian can identify this illness with a laboratory test. Treatment and prevention are similar to those of proliferative ileitis (see Diarrhea, above).

Protozoa are single-celled organisms that can cause illness. Healthy hamsters often carry protozoa in their digestive tracts without being sick, but hamsters that are young or stressed may develop diarrhea as a result of protozoal infections. Your veterinarian can identify protozoa by testing your hamster's feces.

Pinworms, a type of internal parasite, are a rare cause of disease of the digestive tract in hamsters. A veterinarian can diagnose pinworms by examining your hamster or testing its feces. Several types of medication, which often must be mixed with the feed or water, may be prescribed for treatment. The infected hamster’s cage should be thoroughly cleaned and disinfected because the worm’s eggs may still be present.

Tapeworms are relatively common in hamsters as compared to mice and rats. Infected hamsters typically have no signs. When a hamster has a serious case, the tapeworms can cause inflammation and blockage of the intestines and infection of the lymph nodes. A veterinarian can diagnose tapeworm infection with tests of your hamster or its feces and can prescribe appropriate treatment. The cage of the infected hamster should be thoroughly cleaned and sanitized, and whatever may have transmitted the infection (cockroaches, for example) should be eliminated. Rodent tapeworms can infect humans, so it is a good idea to wash your hands thoroughly after handling your hamster or cleaning the cage.


Hamsters may become constipated if they have intestinal parasites such as tapeworms, if they eat their bedding and their intestines get blocked, or if a portion of the intestine folds inside itself, a condition called an intussusception.

Intussusception can be caused by inflammation of the intestines, pregnancy, poor diet, or not enough drinking water. It sometimes causes rectal prolapse, which looks like a tubular structure protruding from the anus. This is considered a medical emergency and requires immediate veterinary attention and surgery. Intussusception is fatal if not treated, and the chances for recovery are guarded even with prompt surgery.

Treatment of constipation requires identifying and treating the cause of the constipation. Intussusception generally requires surgical treatment.


Actinomycosis is an infection caused by the fungus Actinomyces bovis. It is rare in hamsters. This illness can lead to rupture of the salivary glands, which may ooze pus. Your veterinarian can diagnose this illness with a laboratory test. Treatment includes lancing and draining the infected area and prescribing appropriate antibiotics.

Inflammation and Scarring of the Liver (Cholangiofibrosis)

Older hamsters, particularly females, sometimes have longterm inflammation and degeneration of the liver (cirrhosis). Blood tests show increases in enzymes produced by the liver. The cause of the disease is unknown, and there is no effective treatment.

Eye and Ear Disorders

Conjunctivitis (pinkeye) is inflammation of the eye that can result from injury, bacterial infection, or irritation from dust. Conjunctivitis can also occur along with swelling of the face caused by injury, overgrown or diseased teeth, or teeth that are not aligned properly. Warm water can be used to help gently remove crusted material from around the eyes. Your veterinarian may flush the affected eye with saline solution and may prescribe an antibiotic ointment or other treatment.

Protrusion of the eyeball from the socket is common in hamsters. It can be caused by infection of the eye or trauma. The condition may also occur when the hamster is restrained too tightly by holding the skin at the back of the neck. This should be considered an emergency that requires veterinary attention. The sooner treatment is given, the more likely it is that the eye can be saved.

Bone, Joint, and Muscle Disorders

Lameness in hamsters is often caused by muscle or tendon strains. Broken bones most often occur when a hamster’s leg becomes trapped in a wire exercise wheel or wire or mesh caging materials. For this reason, solid-surface wheels and cage materials are recommended. Broken bones, including a broken back, may result if the hamster is dropped or falls from a height (such as a table top). Because hamsters are very small animals, broken limbs are difficult to treat. Any time your pet appears in pain or is reluctant to move, seek immediate professional help.

Nutritional Disorders

If a pregnant hamster does not get enough vitamin E, her fetuses can suffer degeneration of the nervous system. When this happens, the pregnant hamster usually delivers weak or stillborn offspring. She may also eat her offspring. Your veterinarian might notice bleeding or swelling in the skull or spine of the offspring. Adult hamsters with vitamin E deficiency can have muscle disorders or weakness, which can lead to paralysis. You can prevent this from happening by providing your pet with an appropriate, balanced diet. If you suspect your hamster is pregnant, check with your veterinarian regarding the amount of vitamin E in her diet.

Lung and Airway Disorders

Because of their small size, lung and other airway disorders in hamsters can quickly become serious. If you notice your hamster is wheezing or having difficulty breathing, see your veterinarian promptly.


Pneumonia, or inflammation of the lungs, is not common in hamsters. When it does occur, it is usually the result of infection with one or more kinds of bacteria, either alone or together with viruses and other types of infectious agents. The bacteria that cause pneumonia are normally present in the respiratory or digestive system in small numbers. These bacteria can multiply and lead to illness when sudden changes in a hamster’s environment, especially temperature, cause stress. Stress makes it harder for a hamster’s body to fight off infection.

Signs that a hamster is sick with pneumonia include pus or mucus oozing from the nose or eyes, difficulty breathing, loss of appetite, and lack of activity. Your veterinarian can diagnose pneumonia by doing an examination or performing laboratory tests. Treatment is usually not effective, but antibiotics can help in mild cases. Other things that can make a sick hamster more comfortable include giving it fluids by injection, keeping its cage warm and dry, and minimizing stress. If several hamsters live together, it is important to remove the sick hamster from the other hamsters and to keep the living area clean and sanitary.

Sendai Virus (Parainfluenza Virus 1) Infection

This virus is rare in hamsters, but it is highly contagious. The virus is spread from one hamster to another by sneezing or coughing. In newborn hamsters, this virus can cause dripping or oozing from the nose, trouble breathing, pneumonia, and death. Adult hamsters usually do not have signs. Bacterial infection can occur simultaneously with the viral infection. Your veterinarian can identify this illness by laboratory tests.

There is no treatment for the virus itself, but your veterinarian can treat the effects of the virus, with fluids under the skin for dehydrated animals, food supplements, and antibiotics if your hamster has a bacterial infection. To prevent infection with this virus, make sure your hamster does not come into contact with sick hamsters or other rodents and keep its cage clean.

Reproductive Disorders

Breeding female hamsters may have smaller litters or become infertile as a result of old age, malnutrition, a cold environment, too little nesting material, or an abnormal estrous cycle. Hamster reproduction is sensitive to the seasons and the cycle of light throughout the day and night. Also, a male and female pair may simply not be compatible. Hamster fetuses may die in the womb, and pregnant females may abandon or eat their offspring for a variety of reasons. These include eating a poor diet, having a large litter, being in a crowded or noisy environment, being handled too often, having a male in the cage after birth, not having enough nesting materials, not producing enough milk, having inflamed milk glands, or having sick or deformed offspring.

Milk (mammary) gland infection is usually caused by Streptococcus bacteria. Infection usually becomes obvious 7 to 10 days after the female gives birth. Affected milk glands are swollen and may discharge pus or mucus. Mothers may eat their young as a result of this condition. Your veterinarian can identify the cause of the infection with a laboratory test and may prescribe antibiotics for treatment.

Skin Disorders

Many skin disorders are caused by infections or parasites. You can help keep your hamster healthy by regularly checking its skin for signs of hair loss or other problems.

Skin Abscesses

Skin abscesses are infected pockets of pus under the skin. They are usually caused by bacterial infection of wounds received during fighting with cage mates or from injuries caused by sharp objects in the cage. Abscesses are often located around the head. If the lymph nodes around the neck are swollen, there may be an infection in the hamster’s cheek pouches. In male hamsters, the flank glands over the hips may be infected. Wood shavings from bedding can injure the feet or shoulders, which can lead to infection.

The type of bacteria causing the abscess is identified by a laboratory test. Treatment includes draining the abscess and administering an antibiotic. For abscesses that have burst, your veterinarian will make sure all of the contents of the abscess have drained and then flush the wound. Abscesses that have not ruptured can be surgically removed. Your veterinarian may inject antibiotics under the skin. If flank glands are infected, your veterinarian may shave the area around them, clean them, and apply ointment containing antibiotics and steroids. Fighting hamsters should be separated from one another. Make sure your pet’s cage has no sharp edges. Avoid bedding with wood shavings.

Hair Loss (Alopecia)

Patchy hair loss can have many causes in hamsters. These include constant rubbing on parts of the cage, not enough protein in the diet, and hair chewing by cage mates (known as barbering). Hair loss may also be a sign of a type of T-cell lymphoma (a form of cancer) that involves the skin. This is relatively common in hamsters ( see Cancers and Tumors, below). Infestation with mites, tumors in the adrenal glands, thyroid gland imbalance, and problems with the kidneys are rarer conditions that can also cause hair loss.

Hair loss, hamster


Despite its name, ringworm is not caused by worms. Ringworm occurs when a hamster’s skin becomes infected with a fungus. The most common ringworm-causing fungi are Trichophyton mentagrophytes and Microsporum species. Some hamsters have no signs. Other hamsters may have bald patches that can be crusty, flaky, and red around the edges. Hamsters become infected by contact with infected animals or humans or from contaminated objects such as bedding. Hamsters that spend time outside their cages may also be exposed to the fungi in your home. Your veterinarian can diagnose this condition by physical examination and laboratory tests. Treatment may include topical or oral antifungal agents.

Diseases that can be Spread from Hamsters to People

  • Lymphocytic choriomeningitis virus

  • Ringworm

  • Salmonellosis

  • Pseudotuberculosis

  • Tularemia

  • Tapeworms

Ringworm is contagious to humans and other animals. If you suspect ringworm, be sure to wash your hands thoroughly after contact with your pet. Use disposable gloves when cleaning your pet’s cage and its contents and wash your hands thoroughly after cleaning the cage.

Skin and Fur Mites

Infestation with mites is common in hamsters. The 2 species of mite that are most common are Demodex criceti and Demodex aurati. This condition is more common in males and older hamsters because these groups are more prone to malnutrition and other diseases. When an animal is heavily infested with mites, its skin becomes inflamed, dry, and scaly, with hair loss over the back and rump area. Bald areas are dry and scaly but not itchy. Treatment is typically with topical medications.

Other species of mites that are less common in hamsters include ear mites, nose mites, and tropical rat mites. Hamsters infested with ear mites can have inflammation of the skin around the ears, face, feet, and tail. Your veterinarian can identify this condition by testing skin scrapings or hair and administer appropriate treatment. The bedding of the infested hamster should be changed often and the cage should be thoroughly cleaned and disinfected.

Kidney and Urinary Tract Disorders

Inflammation of the kidneys, which worsens over time, is more common in older and female hamsters. Hamsters with this condition lose weight, produce more urine than normal, and are unusually thirsty. The condition may be caused by viral infection, high blood pressure in the kidneys, or a disorder of the immune system. Sick hamsters may also have amyloidosis (see below).

Diseases Affecting Multiple Body Systems

Some diseases, including many infections, affect more than one body system. These are also known as generalized or systemic diseases.

Lymphocytic Choriomeningitis Virus (Arenavirus) Infection

This virus usually infects wild mice; hamsters become infected with it only occasionally. The virus is spread by contact with an infected rodent’s urine or saliva or through tiny droplets spread when sick rodents sneeze or cough. An infected pregnant hamster can pass it to her fetuses in the womb. The virus does not usually make hamsters sick, and it goes away on its own. However, sick hamsters can pass the virus to humans. Some hamsters that have this virus lose weight over time. Additional signs include convulsions, depression, and decreased reproduction in females. Your veterinarian might notice an enlarged liver, spleen, kidneys, or lymph nodes. The virus can be detected by laboratory tests. There is no effective treatment. Animals that are sick with arenavirus should be euthanized, and their living quarters must be thoroughly cleaned and sanitized. Any contact between your pet and wild rodents must be eliminated.

This virus is very contagious and very dangerous for humans. It can cause flu-like signs and inflammation of the brain, the membrane around the brain, and the spinal cord. Infection can spread to a fetus if a woman becomes infected during pregnancy; birth defects or miscarriage can result. To protect yourself and your family, wear disposable gloves when cleaning an infected hamster’s cage. Be especially cautious about handling bedding and other materials that may contain urine. After you have finished cleaning the cage and all of its contents, dispose of potentially contaminated materials carefully (use gloves and place the materials in sealed plastic bags), then follow up with thorough handwashing, including your arms. Immediately wash any clothing that may have come in contact with contaminated bedding or other items.


Amyloidosis is a condition in which the body produces a dense protein called amyloid. Amyloid accumulates in various organs, such as the liver and kidneys, and eventually interferes with the functions of these organs. This condition may affect hamsters that are more than 1 year old or those with longterm illnesses. It is more common in females. Hamsters with this condition usually do not appear sick until their kidneys stop working because of amyloid deposits. Kidney failure causes a buildup of chemicals in the blood, leading to loss of appetite, a rough hair coat, hunched posture, accumulation of fluid in the body, depression, and death. Blood tests may show an increase in the proteins albumin and globulin, too much protein in the urine, and high cholesterol. There is no treatment for this illness except to make the hamster more comfortable (by giving it fluids, for example). Most hamsters with this illness live only a short time.

Polycystic Disease

Polycystic disease, which causes hamsters to develop fluid-filled sacs called cysts, is common in hamsters older than 1 year. Affected hamsters usually develop 1 or more small cysts in the liver. Other organs that can have these cysts are accessory sex glands in males, the pancreas, the ovaries, the uterus, and the adrenal glands.


This illness is caused by the bacterium Yersinia pseudotuberculosis. Hamsters are exposed to these bacteria when the feces of wild birds or rodents contaminate their food or drinking water. Infected hamsters can develop serious illness such as blood infection. Affected hamsters may have longterm, extreme weight loss with occasional diarrhea. Your veterinarian might notice degeneration of the lymph nodes, spleen, liver, lungs, gallbladder, and the walls of the intestines. The bacteria can be detected with laboratory tests. There is no treatment.

Pseudotuberculosis is contagious to humans, so any hamsters that have this disease or that have come into contact with infected hamsters must be euthanized. Contact with wild rodents or birds must be eliminated. The sick hamster’s cage must be thoroughly cleaned and sanitized. Be sure to wear gloves when cleaning the cage, and dispose of contaminated materials. Wash your hands and arms thoroughly when finished.


Tularemia, caused by infection with the bacterium Francisella tularensis, is rare in hamsters. It can cause blood infection, with a high rate of severe illness and death. Hamsters catch this illness from infected ticks or mites. Sick hamsters may have a rough hair coat. Hamsters with tularemia die within 48 hours of becoming ill. Infection causes bleeding in the lungs and enlarged liver, spleen, and lymph nodes. There is no treatment. This disease is contagious to humans, so any infected hamsters—or hamsters that have been exposed to infected hamsters—must be euthanized. The sick hamster’s cage must be thoroughly cleaned and sanitized. Use gloves and dispose of bedding and other cage materials carefully. Minimize your pet’s exposure to ticks and promptly treat any evidence of mite infestation to reduce the chance of developing tularemia.

Cancers and Tumors

Malignant, or cancerous, tumors occur in only a small percentage of hamsters. Both genetic and environmental factors may play a part in development of the disease. Most growths in hamsters are not cancerous and occur in organs that produce hormones or digest food. The most common location for these benign tumors is the adrenal gland, which is near the kidney.

Lymphoma may occur in older hamsters, with tumors in the lymph nodes, thymus, spleen, liver, and other sites. A type of T-cell lymphoma affects the skin in adult hamsters, causing low energy, weight loss, patchy hair loss, and skin inflammation.

Other tumors can develop in the uterus, intestines, brain, skin, mammary glands, hair follicles, fat, or eyes. If you find an unexpected lump on your hamster, have your pet checked by a veterinarian promptly. The sooner a tumor is discovered, the easier it is to treat.

For More Information

Also see professional content regarding disorders and diseases of hamsters.

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