Small Rodents: External & Internal Parasites and Disease

External parasites

Lice, fleas, and mites are all possibilities when your pet constantly scratches or bites its fur. The treatment for all three is the same: a dusting powder that is safe for use on cats or hamsters. If, while the animal is restrained, you can examine the fur and find either fleas themselves or “flea dust,” the tiny pepper-like residue they leave in their wake, its cage should be emptied and sprayed with the dusting powder before new material is put in, and the animal should be sprayed or powdered.

Internal parasites and disease

The similarity between the symptoms of some internal parasites and bacterial or viral infections makes it impossible to deal with these conditions apart from other possible causes.

Any sign of poor health should be an immediate signal to observe the animal carefully and separate it from others of the same species. Supplying the veterinarian with an accurate case history to aid in diagnosis is important. Keep the sick animal clean and warm and supply fresh food and water in the meantime.

ASSISTING YOUR VETERINARIAN. Diagnosis is essentially a job of detection in which the veterinarian needs all the clues possible to arrive at a correct diagnosis. Ideally, you should start accumulating information before anything goes wrong.

Small mammals have few means of communicating what they feel, but their bodies are constantly giving us data, if we can read them, on the state of their health. To properly evaluate them, you should keep some simple records. Record-keeping is the best way of detecting health problems.

One of the most important pieces of information you should gather deals with your pet’s weight. Once matured, the animal should maintain its weight. Immature animals should show a steady increase in weight. A failure to do so or a loss of weight in a non-hibernating adult probably indicates a problem. (Of the animals discussed, only hamsters hibernate. In captivity, this will not occur if their environment is kept at the recommended temperature.) A weight scale marked in grams (available for measuring food in small portions) should be used for weighing small pets such as mice, hamsters, and gerbils. A scale marked in ounces and pounds can be used for guinea pigs.

Growth weights can be taken every other day for very young animals, while adults can be weighed weekly.

The list of diseases below will allow you, depending on the type of animal you own, to relate the findings on your checklist to possible causes — both in terms of the care the animal is receiving and infectious conditions known in the species.


RESPIRATORY SYSTEM. Sneezing and labored breathing could be caused by viral, bacterial, or fungal infections. They can show up in animals of all ages and usually follow stress. To arrive at a definitive diagnosis, your veterinarian may rely on physical examination, cultures, and radiography. Antibiotics are usually used in treatment. Chances of recovery depend on the individual case.

EYES. In older animals, conjunctivitis (pinkeye)* and swollen eyes may occur. Treatment such as mild ophthalmic ointment may be dispensed by your veterinarian.

DIGESTIVE TRACT. Mild diarrhea can be due to a number of causes. There is the possibility that it may be a result of diet, or parasitism. Unwashed greens, intestinal parasites (most unlikely in gerbils), protozoan or salmonella infection can be a cause (this is not the usual type of salmonella that infects humans).

SKIN AND COAT. Scanty or patchy hair growth in unweaned young is not uncommon. No cause is known for this condition but hair will grow in as the animal gets older.

Nose and jaw inflamed and ulcerated — while dermatological problems cannot be ruled out, these symptoms are usually traceable to mechanical abrasion. The cage should be checked and any sources of irritation removed.

Bare spots on base of tail of mature animals usually indicate that they are fighting as a result of overcrowding. Correcting this condition will automatically bring the fights to an end.

NERVOUS SYSTEM. Some younger animals are especially prone to seizures when they are being handled. The body becomes rigid and the legs stiffen and tremble. As the animal gets older, the seizures become less, frequent The cause is believed to be a form of catalepsy.


EYES. Runny eyes, sneezing, nasal discharge, and a tendency to huddle may be due to either bacterial or viral infection. Young animals are particularly susceptible. Deaths are not frequent. Treatment relies on antibiotics.

DIGESTIVE TRACT. Mild diarrhea in mature animals that appear otherwise healthy is often an indication of a protozoan infection. Your veterinarian will probably prescribe a high-protein diet if a microscopic examination of the stool proves negative. Deaths are infrequent.

Diarrhea-stained anus, lethargy, difficulty in breathing, and protrusion of the colon through the anus (intussusception and prolapse of colon) are the classical symptoms of a disease called “wet tail.” The exact cause is unknown, but factors believed to be influential are a possible infectious agent, viral and/or bacterial, improper caging, overcrowding, and lack of fresh water. Improved care, antibiotics, and even surgery are used in treatment, but fatalities are high.

SKIN AND COAT. Loss of hair, especially around the face, is probably an indication of mites. Itching is not a major problem. A special safe ointment prescribed by your veterinarian may correct this problem.

NERVOUS SYSTEM. Partial paralysis, inability to lift the head, and abnormal crawling can occur in mature hamsters. Degenerative nervous and muscle diseases can cause these symptoms. Nutritional problems also can mimic these signs. Administering vitamin D may be effective, although recovery rate is poor.

Mice and Rats

RESPIRATORY SYSTEM. Sneezing, labored breathing, a runny nose at which the animal paws, unkempt coat, and a general appearance of poor health — these make up the clinical picture describing a number of diseases in mice and rats. They may be controlled with antibiotics, but can recur and become long-term problems.

* Not contagious to humans.

DIGESTIVE SYSTEM. Mustard-colored stains around the tail of a nursing mouse or rat and running stools are indications of a common and highly fatal disease. Prime attention should be given to preventing its transmission by placing filter caps over the top of the cage.

Mild diarrhea in an otherwise healthy adult mouse or rat is a common symptom that may be due to protozoan infection, usually treated with a diet of apples, cabbage, and ground beef and the administration of antibiotics.

SKIN AND COAT. Scratching around the head and ears, abrasions, scabs, and bald spots are indicative of mites, which are common in mice. Insecticide strips (dichlorvos or pest strips) and powder are usually effective in combating them.

Sores around the ears and on the ear tips in mature animals are usually the result of fighting among the males. Simple observation will confirm this and they can be separated.

NERVOUS SYSTEM. A tilted head and a tendency to go in circles may be suggestive of a bacterial infection of the inner ear, sometimes associated with an upper respiratory infection. Antibiotics are used in treatment.

Guinea Pigs

LYMPH AND RESPIRATORY SYSTEMS. “Lumps,” a disease named for the swollen lymph glands on animals that appear otherwise healthy and active, is usually a streptococeal infection. Often the lymph nodes will discharge pus and must be drained. The animal must be separated from other guinea pigs and may be given antibiotics — but cautiously. Oral antibiotics, especially penicillin, given to guinea pigs may cause sudden death by killing off good bacteria.

Difficulty breathing, a ruffled coat, runny nose, dried mucus on the inside of the foreleg, and itching conjunctivitis are among the symptoms of a number of bacterial infections, the most common being a streptococcal infection. Your veterinarian can isolate the specific cause with a culture and use antibiotics in treatment, but fatalities are high.

DIGESTIVE SYSTEM. Difficulty chewing or moving the mouth, slobbering when eating, and overlong molars can be the results of malocclusion. Your veterinarian may attempt to solve the problem temporarily by cutting and filing the teeth.

Blood-tinged diarrhea may be indicative of protozoan parasites. In young animals it is sometimes fatal. Your veterinarian may prescribe medication along with supportive care.

Poor weight gain, a rough coat, low resistance to disease, a tendency to huddle, and reluctance to move about are some symptoms that may occur with a vitamin C deficiency. Your veterinarian will check over the diet the animal is receiving and may increase its intake of ascorbic acid through injections, or by supplements in the water and food, as well as adding such items as kale, cabbage, citrus fruits, and orange juice to the diet.

SKIN AND COAT. Generalized bald spots or patchiness without itching is usually associated with a stress situation. No specific cause is known and if other dermatological causes are ruled out, treatment usually consists of a diet of hay, cabbage, or kale.

Scaly, patchy skin lesions and broken hair shafts with itching can be symptoms of a fungal infection. Since ringworm fungus may be the cause, the animal should be handled with disposable gloves, for this condition is communicable. Griseofulvin is used in treatment but cautiously, because of the possibility of a reaction to Penicillium cultures, from which it is derived.

Sores on the hocks or soles of the feet and abscesses are usually the result of infections resulting from the abrasions of a wire cage floor. The animal should be put on a softer surface and the affected areas treated daily with medicated dressings.

Also see: Parasitic Worms: An Untapped Potential for Bio-medicine?

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