Furnishing 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 occur in hamsters inside one of the upper chambers of the heart. This condition is called atrial thrombosis. The blockages are often found in the left side of the heart.
Congestive heart failure, a condition in which the heart muscle weakens and cannot pump blood efficiently throughout the body, also affects hamsters (see Heart and Blood Vessel Disorders of Dogs: Heart Failure in Dogs). Both of these conditions happen more frequently in older female hamsters and are often connected with amyloidosis (see Hamsters: Amyloidosis). Signs include shortness of breath, an irregular heartbeat, and a blue tint to the skin. There is no effective treatment; however, your veterinarian may be able to suggest ways of managing this condition for a period of time.
Diarrhea is one of the most common digestive system problems in hamsters and can be caused by several different disorders. Diarrhea in hamsters is also sometimes called “wet tail” because of how a hamster looks when it has diarrhea. Constipation is another common digestive problem in hamsters.
Proliferative enteritis, an inflammation that spreads throughout the small intestine, causes diarrhea in hamsters. The culprit is the bacteria Lawsonia intracellularis, which is most likely to infect hamsters that are stressed due to being transported, living in an overcrowded cage, surgery or illness, or changes in diet. The condition is more common in young hamsters and occurs rapidly. Many hamsters with this infection get very sick and die quickly. Usually, the fur around the tail and belly is wet and matted. Common signs of this disease include low energy levels, loss of appetite, and weight loss.
Your veterinarian will likely make a diagnosis using the signs and history, and the animal's positive response to treatment. To treat a hamster with this condition, your veterinarian may give it fluids (either by mouth or by injection) in case it is dehydrated, and possibly antibiotics, which can be mixed into the hamster's drinking water. 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's disease, a digestive illness caused by the bacteria Clostridium piliforme, can have many of the same signs as proliferative enteritis, above. These include loss of appetite, dehydration, watery diarrhea, and sudden death. Hamsters catch 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. A certain group of antibiotics, known as gram-positive spectrum antibiotics (some examples are lincomycin, clindamycin, ampicillin, vancomycin, erythromycin, penicillin, and cephalosporins), can be fatal for hamsters. These medicines can cause inflammation of the small intestines, resulting in diarrhea and death within 2 to 10 days. They kill the bacteria that usually live in a hamster's digestive tract and allow the overgrowth of other bacteria. The pouch at the end of the small intestines (called the cecum) becomes swollen with fluid, and the hamster bleeds from inside its intestines. Your veterinarian can diagnose this problem by finding out what medications your pet has taken recently, and doing special 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. One possible treatment your veterinarian may suggest is force-feeding the sick hamster feces from a hamster that is not sick; these “healthy” feces may help to re-establish the proper balance of bacteria in the sick hamster's intestines.
Salmonellosis, an inflammation of the intestines caused by Salmonella bacteria, is not common in hamsters. The signs and treatment approach for this disease are described in the gerbil chapter (see Gerbils: Salmonellosis).
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 special laboratory test. Treatment and prevention are similar to that of proliferative enteritis (see Hamsters: Diarrhea).
Protozoa are a special kind of single-cell animal, different from bacteria and viruses, that also cause illness. Healthy hamsters often carry protozoa in their digestive tracts without being sick, but hamsters that are young or stressed may develop intestinal infections and diarrhea as a result. Your veterinarian can identify this illness by doing a test on your hamster's feces. Treatment includes adding the medication metronidazole to your pet's drinking water.
Pinworms, a type of internal parasite, are a rare cause of disease of the digestive tract in hamsters. Diagnosis and treatment are as described for gerbils (see Gerbils: Pinworms).
Tapeworms are relatively common in hamsters 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. Diagnosis and treatment are described in the chapter on gerbils (see Gerbils: Tapeworms).
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 is sometimes seen as a tubular structure that protrudes 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. It may be necessary to surgically remove a portion of the intestines, or to create a bypass between 2 portions of the intestines that are not normally connected.
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 suffer from longterm inflammation and degeneration of the liver (cirrhosis). Blood tests will 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 (pink eye) is an inflammation of the eye or swelling of the face that may be the result of injury, overgrown or diseased teeth, or teeth that are not aligned properly. It may also be caused by a bacterial infection, irritation from dust in the bedding, or bite wounds. Warm water can be used to help gently remove crusted material from around the eyes and open eyelids. 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 occur due to an infection of the eye or from 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, it is time to seek immediate professional help.
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 by themselves or together with viruses and other types of infectious agents. The bacteria that often cause pneumonia are normally present in the respiratory or digestive system in small numbers. These bacteria can multiply and lead to illness, however, 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 on the discharge. 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 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.
Breeding female hamsters may have smaller litters or become infertile as a result of old age, malnutrition, a cold environment, not having enough nesting material, and not having a normal 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.
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 developing problems.
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 glands over the hip called hypersecretory flank glands may be infected. Sometimes wood shavings from bedding can injure the feet or shoulders, which can lead to infection.
The particular type of bacteria causing the abscess is identified by a laboratory test. Treatment includes draining the abscess and antibiotics. For abscesses that have burst, your veterinarian will make sure all of the contents of the abscess have drained, and then flush the wound with an antibiotic liquid. Your hamster may also require antibiotic ointment. Abscesses that have not ruptured can be surgically removed and 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 with 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 Hamsters: Cancers and Tumors). Infestation with mites, tumors in the adrenal glands, a thyroid gland imbalance, and problems with the kidneys are rarer conditions that can also cause hair loss.
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 Tricophyton mentagrophytes and Microsporum species. Some hamsters have no signs. Other hamsters may have bald patches. These may be crusty, flaky, and red around the edges. Hamsters catch the disease from other animals or humans who are infected, or from infected 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 examining your pet, looking at the red spots under a special lamp, and by a laboratory test of hairs from the infected spots. To treat ringworm, your veterinarian may prescribe an antifungal ointment, a scrub made with iodine, a medicine to take by mouth called griseofulvin, and may shave the affected areas.
Ringworm is contagious to humans and other animals. If you suspect ringworm, be sure to wash your hands thoroughly following contact with your pet. Use disposable gloves when cleaning your pet's cage and its contents and wash your hands thoroughly following the cage cleaning.
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 includes a prescription shampoo that contains selenium sulfide or an ointment that contains the medicine amitraz.
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 with a laboratory test on scrapings from the infected skin or hair. Treatment for these types of mites includes the medicine ivermectin. The bedding of the infested hamster should be changed often and the cage 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 Hamsters: Amyloidosis).
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 by 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, or kidneys, or swollen 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. 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 sheets of dense protein called amyloid. The protein deposits build up in various organs, such as the liver and kidneys, and eventually interfere with the normal functions of those organs. This condition may affect hamsters that are more than 1 year old, or hamsters 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, which can, in turn, lead 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.
This disease, which causes hamsters to develop fluid-filled sacs called cysts, is common in hamsters more than 1 year old. Usually, the hamster develops 1 or more cysts in its liver. The cysts are 3 centimeters or less in diameter. Other organs that can develop these cysts include accessory sex glands in males, the pancreas, the ovaries or the tissue lining the womb in females, and the adrenal glands.
This illness is caused by the bacteria Yersinia pseudotuberculosis. Hamsters are exposed to the bacteria when the feces of wild birds or rodents get into their food or drinking water and can develop serious illness. Infection in hamsters usually leads to blood poisoning. Another sign is 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 with this disease, or any hamsters that have come into contact with them, 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 disposing of contaminated materials. Wash your hands and arms thoroughly when done.
This disease, caused by infection with the bacteria Francisella tularensis, is rare in hamsters. It can cause blood poisoning, 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, and die within 48 hours of becoming ill. Your veterinarian might notice 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 (see Hamsters: Skin and Fur Mites) to reduce any chance of developing tularemia.
Cancers and Tumors
Malignant, or cancerous, tumors occur in only about 4% of hamsters. Both genetic and environmental factors may play a part in development of the disease. Most hamster tumors are not cancerous and occur in organs that produce hormones or digest food. The most common location of these benign tumors is in 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 that affects the skin occurs in adult hamsters, with signs of low energy, weight loss, patchy hair loss, and skin inflammation.
Other tumors can develop in the womb, intestines, brain, skin, hair follicles, fat, or eyes. If you find an unexpected lump or bump on your hamster, have your pet checked by a veterinarian promptly. The sooner a tumor is discovered, the easier it is to treat.
Last full review/revision July 2011 by Katherine E. Quesenberry, DVM, MPH, DABVP (Avian); Kenneth R. Boschert, DVM, DACLAM