Diseases in Rodents

By Gregory Rich, DVM; Laurie Hess, DVM; Rick Axelson, DVM

What are some of the common diseases of pet rodents?

Common conditions of pet rodents include skin diseases, respiratory diseases, gastrointestinal problems, dental problems, and cancerous growths (tumors).

What types of skin conditions do rodents get?

Rodents may be infected with lice or skin mites. These external parasites cause itchy, flaky skin and generalized hair loss. Lice may be seen with the naked eye and nits (egg casings in the base of hair shafts) may be see in some cases.

Ringworm, a fungal infection of the skin, causes circular patches of hair loss with scaly skin or scabs in the center of the hair loss. Lumps and bumps on or under the skin is generally a sign of some form of cancer. Some skin cancers are solitary nodules, while others may affect several locations on the body. (Image shows chinchilla with ringworm; photo courtesy of Gregory Rich, DVM.)

Guinea pigs may get a condition called pododermatitis, which is an infection of the bottom of their foot pads. These infections are very painful and need veterinary attention to resolve properly. Nasal dermatitis is a skin condition specific to gerbils. This condition causes irritation and hair loss in a circle around the nose.

What are the signs of respiratory infections?

In mild infections, signs include nasal and/or ocular (eye) discharge, which may advance to wheezing, coughing, and open-mouth breathing in severe infections. When the infection spreads to the lungs, the disease is referred to as pneumonia. Animals with pneumonia often have a pronounced difficulty in breathing, stop eating, and become lethargic.

Bordetella is a type of bacteria that causes respiratory infections in guinea pigs and can prove fatal if not treated promptly. Since rabbits carry this organism without showing signs of illness, rabbits and guinea pigs should not be housed together. In mice and rats, respiratory problems are often caused by a type of bacteria called Mycoplasma, which can cause many respiratory signs and often leads to chronic respiratory disease.

Other infectious agents, such as Pasteurella and Streptococcus bacteria, can also cause pneumonia. In rats, more than one type of bacteria may cause the respiratory disease and many rats are also infected with Sendai virus, which will render a complete cure of symptoms very difficult.

Regardless of the exact cause of respiratory disease in pet rodents, respiratory infections are relatively common. Several factors may irritate the respiratory tract and predispose a pet rodent to a respiratory infection, including dusty cage litter, aromatic cedar chip bedding, and high levels of ammonia from urine accumulation in dirty litter or a dirty cage. These factors should be corrected to reduce the incidence of respiratory problems. Stress from overcrowding and cage mate aggression may play a role in immunosuppression that leads to a respiratory infection.

What gastrointestinal diseases do pet rodents get?

Gastrointestinal (GI) disease is common in pet rodents. GI disease includes diarrhea (commonly known in small rodents as ”wet tail”) from causes such as bacterial or parasite infections, and gastrointestinal stasis (a slowing down of food through the GI tract due to changes in the normal GI bacteria). In hamsters, Lawsonia bacteria is known to cause a severe, life-threatening intestinal infection. All rodents are susceptible to intestinal infection with Giardia, a protozoal parasite.

"Rodents with GI disease also may have decreased appetites and lethargy."

Rodents with GI disease also may have decreased appetites and lethargy. As with other exotic pets, the sooner a rodent showing these signs is seen and treated by a veterinarian familiar with rodents, the sooner the cause of illness may be determined and treated, and the better the prognosis.

Can rodents have dental problems?

All rodents have teeth that grow continuously throughout their lives. Occasionally, these teeth grow too long and cut into the gums, causing pain and possibly preventing the mouth from closing properly, which eventually causes the pet to stop eating. Sometimes pets with overgrown teeth will drool or have a constantly wet chin (slobbers). The front teeth or incisors are most frequently the problem in small rodents, such as rats and mice, and their excessive length interferes with eating and grooming.

Sometimes, guinea pigs and chinchillas have overgrown molars or cheek teeth, which makes eating challenging or even painful. These overgrown teeth often form points or sharp edges on their sides which may cut into the tongue or cheeks. Chinchillas’ teeth often become diseased underneath the gumline and become impacted, like wisdom teeth in people. This process in turn makes eating extremely painful.

Do rodents get cancer?

Just as in people, cancer is a common ailment in pet rodents. Mammary (breast) tumors are one of the most common types of cancer, especially in rats and mice. Amazingly, breast tissue in these pets covers most of the underside of the body, so breast cancer can appear anywhere from the neck to the groin. Mammary tumors can grow rapidly and need to be removed surgically. Fortunately, many mammary tumors are benign, and the prognosis after surgery is good, but recurrence is common. Rodents can get many other types of tumors as well. Hair follicle cysts or tumors in guinea pigs, called Trichoepithelioma, are very common. Mycosis fungoides is a specific type of skin tumor found to affect hamsters.

How are rodent diseases treated?

Respiratory diseases are typically diagnosed based on clinical signs. X-rays can be taken to confirm a diagnosis. With infectious diseases, medications are generally prescribed, including antibiotics and anti-inflammatory drugs. Supportive care in the hospital, including syringe-feeding and fluid therapy, as well as oxygen therapy, may be needed for pets with difficulty breathing or serious infections such as pneumonia.

Rodents with signs of gastrointestinal disease often require X-rays, blood tests, cultures, a microscopic examination of feces for parasites, or other tests to help reach a specific diagnosis. Pets that are dehydrated from diarrhea or that have a decreased appetite are typically given subcutaneous or IV fluids and are syringe-fed liquid nutrients. These pets are treated with appropriate medications, such as antibiotics and anti-parasitic drugs, depending on the cause of their signs. Mildly affected pets may be treated at home, while more severely affected pets may need to be admitted to the hospital for treatment.

Regardless of the signs of disease in your pet rodent, pet store antibiotics are generally ineffective and should never be used. Treatment with the wrong medication may cause the disease to worsen or, in the case of a bacterial infection, may cause the bacteria to become resistant to certain medications in the future. Sick rodents should be examined by a veterinarian knowledgeable about rodent diseases as soon as possible and administered appropriate treatment under the veterinarian’s guidance.

Overgrown teeth need to be trimmed. Trimming the incisors is often done under anesthesia, with a drill. Nail clippers or wire cutters should never be used to trim teeth as these techniques often result in broken teeth, leading to dental abscesses or other serious problems. The diagnosis of overgrown molars (cheek teeth) usually requires X-rays and a thorough oral examination under anesthesia. Treatment typically involves the use of special dental instruments to file down the molars with the pet under anesthesia. Dental disease can often be prevented in rodents by keeping them on a proper diet and offering them safe objects on which to chew, such as blocks of untreated wood.

Tumors are removed surgically under anesthesia and tested to determine their cause. Intra-abdominal tumors can often be removed, but the procedure is more invasive and challenging than for removal of external tumors. The smaller the tumor and the earlier it is removed, generally the easier the surgery.

How can I tell if my pet rodent is sick?

Most rodents are prey species that naturally hide their signs until they are very ill. In addition, while some signs of disease in rodents are specific for a certain disease, most are vague and non-specific, such as a rodent with a decreased appetite and lethargy. These signs can be seen with many diseases including pneumonia, cancer, and even kidney or liver failure. Any change from normal is a cause for concern and an indication that your rodent requires immediate evaluation by your veterinarian. Early diagnosis and treatment will generally be less costly and should allow for quicker return to good health.

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