This is commonly seen in the hystricomorphs and is thought to have a similar aetiology to dental disease in rabbits. Clinical signs, diagnosis and corrective dentistry and prevention are as described for rabbits. (see rabbit notes). Incisor malocclusion occasionally seen in mymorphs. 

Dermatoses 

Commonly seen in these species. Parasitic (fur mites, Demodex spp. lice), endocrine and neoplastic skin disease are common. Clinical signs due to ectoparastism are ogten secondary to immunosuppressive conditions eg concurrent disease, old age. Treatment for most ectoparasites is with systemic or topical ivermectin or selamectin.

Mammary tumours are common in rats ( benign fibroadenomas) and mice ( aggressive adenocarcinomas). 

Cystic ovarian disease is extremely common in aged female guinea pigs (a 76% incidence in animals between 1.5-5 years old has been reported). The aetiology is unknown, although oestrogenic substances in hay have been implicated. Initially cysts may be asymptomatic, however as they increase in size, non-pruritic alopecia develops over the back and symmetrically over the flanks. Abdominal enlargement and infertility may also be evident. Diagnosis is based on history, abdominal palpation, radiography and ultrasonography. The cysts are usually bilateral and may be up to 10cm in size and painful on palpation. They are often associated with concurrent cystic endometrial hyperplasia, mucometra, endometritis and fibroleiomyomas. Ovariohysterectomy is indicated, however the use of human chorionic gonadotrophin, at a dose rate of 100iu hCG IM repeated in 7-10 days for 1 - 3 weeks, has been reported to temporarily resolve this condition. Percutaneous drainage of the cysts may also be possible under anaesthesia.

It is common to see sows with non-pruritic bilateral flank alopecia during late pregnancy. Hair loss due to telogen defluxion, associated with intensive breeding, is thought to be due to reduced anabolism of maternal skin, associated with foetal growth and reverses following parturition. Diagnosis is based on reproductive history and ruling out other causes of alopecia such as dermatophytosis, barbering, vitamin deficiencies, ovarian cysts and ectoparasites. 

Cystic ovarian disease: Gerbils 

are common in older female gerbils (50% incidence >400 days old). Cysts vary in size, but can grow up to 5cm in diameter and are often bilateral. Reproductive performance is reduced and eventually the gerbil will become infertile. Symmetrical alopecia and poor coat quality is seen clinically. Abdominal distension occurs in severe cases, often associated with dyspnoea. Diagnosis is based on clinical signs, abdominal palpation, abdominal radiography or ultrasonographic examination. Drainage by fine needle aspiration under general anaesthesia may be attempted, but ovariohysterectomy is the treatment of choice. 

Diabetes mellitus: Guinea pigs, degus, chinchillas and hamsters  

 has been reported in guinea pigs. Possible aetiologies include an unclassified infectious agent in Abyssinians (possibly viral in origin), hereditary factors, congenital manganese deficiency in juveniles and high sugar, high carbohydrate diets, such as apples and carrots, which exacerbate the problem.

Clinical signs are seen in juvenile guinea pigs 3-6 months old, but also geriatric guinea pigs and chinchillas. Clinical signs are as for other species reduced appetite, depression, anorexia, weight loss, polyuria, polydipsia and early cataract formation, infertility, foetal mortality and stillbirths reported in breeding colonies. Diagnosis is based on elevated blood glucose levels (>20mmol/L), hyperlipidaemia and results of glucose tolerance tests. Serum fructosamine levels should be measured to confirm diagnosis (reference range is 215-296 μmol/l in the free-ranging plains viscacha, Lagostomus maximus, a close relative of the chinchilla, reference range for rabbits 188-349 umol/L). A diagnosis of diabetes based solely on serum and urine glucose levels should be viewed with some caution. Other causes of hyperglycaemia, such as stress, should be ruled out prior to making a diagnosis of diabetes. Diabetic cataracts should be differentiated from inherited cataracts in 9-10 month old guinea pigs and cataracts secondary to metastatic calcification. Treatment consists of a high fibre diet. Insulin therapy is rarely indicated and spontaneous recoveries are common. Glipizide 2-5 mg/kg q12h PO titrated to clinical signs and fructosamine levels has been found to be affective. Supportive care with syringe feeding and fluid therapy may be necessary.

Diabetes mellitus is a spontaneous disease occurring in certain genetic lines of Chinese hamster. Clinical signs include weight loss, glucose intolerance, mild to severe hyperglycaemia, glycosuria, ketonuria, polydypsia (normal water intake is less than 10ml/day), polyuria and hyperphagia. Normal blood glucose levels are 7mmol/L in the Syrian hamster. Glucose levels are sensitive to handling and collection technique. Onset of symptoms can be delayed by restricting food quantities to that of a non-diabetic hamster and reducing fat content, replacing animal fat with vegetable fat. Treatment with Neutral Protamine Hagedorn (NPH) insulin, 2IU SC daily is possible. 

Pituitary hyperplasia and adenomas: Rats  

are common in older rats, particularly non-breeding females. Clinical signs include loss of appetite (pituitary cachexia), weight loss, muscle atrophy, chromodacryorrhea, vestibular nerve dysfunction resulting in head tilts, ataxia, circling and fitting. Pituitary neoplasia in rats and mice may lead to excess ACTH release and hyperadrenocorticism. Iatrogenic Cushings may also occur following glucocorticoid therapy. 

Hyperadrenocorticism : Hamsters and gerbils - 

In hamsters both primary hyperadrenocorticism (due to neoplastic changes of the adrenal cortex) and secondary hyperadrenocorticism (due to excess ACTH secretion secondary to a functional pituitary tumour) are been reported. Iatrogenic Cushings may also occur following glucocorticoid therapy. This condition is commonest in males and older animals, with adrenocortical adenoma being one of the most common reported benign neoplasms in the Syrian hamster. Interestingly many of these develop in the zona glomerulosa where mineralocorticoids are primarily produced.

Hyperadrenocorticism has rarely been reported in ageing gerbils. Clinical signs, diagnosis and treatment are as for hamsters. A disease complex has been described in breeding gerbils where development of hyperadrenocorticism appears to be linked with blood vessel mineralisation, myocardial necrosis/fibrosis and diabetes. The exact relationship and aetiology has not been determined, but these lesions often occur simultaneously in breeding animals. 

Hyperadrenocorticism : Guinea pigs 

Hyperadrenocorticism has been reported in the guinea pig, due to adrenocortical neoplasia. Classical signs of Cushing’s disease are present – PU/PD, obesity, lethargy and bilateral symmetrical alopecia. The enlarged adrenal gland may be detected ultrasonographically. Diagnosis can be made by measuring salivary cortisol levels via cotton buds and performing an ACTH stimulation test (20.I.U im). Successful tmanagement is reported with trilostane at 2mg/kg bid. Surgical removal of the adrenal gland is possiboe but rarely performed 

Hypothyroidism in hamsters  

may manifest as alopecia, hyperpigmentation of the skin, lethargy, cold intolerance and thickening of the skin. It reportedly responds to treatment with thyroxine. 

Neurological disease: Guinea pigs, chinchillas & gerbils  

rare in these species, although spontaneous epilepsy, lead toxicity associated with seizures and encephalitis associated with listeriosis and lymphocytic choriomeningitis have been reported in chinchillas. Spontaneous epileptiform seizures are common in certain genetic lines of gerbils. Seizures occur from two to three months of age and may become more severe up to six months of age. They are usually stimulated by a change in environment or handling. If frequently handled within the first three weeks of life, epilepsy may be less likely to develop. Treatment is rarely indicated, however phenytoin and primidone may be used. 

Head tilt 

Common in ageing rodents and is often associated with bacterial infection, secondary to respiratory infections (otitis media, otitis interna). Central lesions also occur, for example pituitary adenomas which are common in older rats and often result in head tilts. In gerbils aural cholesteatoma, papilloma or polyp formation, with secondary bacterial infection are common. There is no treatment. Treatment for bacterial infections with appropriate antibiotics may prevent worsening of clinical signs, but rarely provides resolution. Papilloma or polyps in the external ear canal may be surgically removed although regrowth is possible following incomplete removal. 

Cavian Leukaemia 

Lymphosarcoma is common in guinea pigs and is thought to be associated with Type C retroviral infection. Clinical signs include rough hair coat and lymphadenopathy. Diagnosis is based on haematology (with significantly elevated TWBCC) lymph node aspiration or biopsy and cytology. Abdominal ultrasonography may detect infiltration of visceral organs such as the liver and spleen. The disease rapidly progresses in 2-5 weeks. Chemotherapy has been described and may be useful. Euthanasia is however often indicated. 

Renal Failure - 

Chronic interstitial nephritis is common in ageing rodents, especially rats, and may be associated with weight loss, reduced appetite, polydypsia and polyuria and cystitis. Renal fibrosis, glomerulosis and amyloidosis have also been reported. Diagnosis is based on urinalysis (presence of protein, blood, casts and cells) and biochemistry. Supportive care with fluid diuresis and anabolic steroids may slow the progression of renal failure. Clients should be encouraged to provide fresh water and food at all times and to avoid stressful situations which could predispose to acute renal failure. A low protein diet can be used in omnivorous species (rats and mice) 

Cardiomyopathy: chinchillas & hamsters 

Heart murmurs are commonly encountered in chinchillas and may vary from mild to moderate. These may be clinically insignificant. Further investigation is warranted if clinical signs such as syncope or respiratory signs are seen. HCM and tricuspid regurgitation have been described in chinchillas. Cardiomyopathy and left atrial thrombosis has been reported in hamsters. Treament is extrapolated from canine and feline medicine.