Care and Common Ailments of Small Exotic Mammals

Vet Times The website for the veterinary profession https://www.vettimes.co.uk

Care and common ailments of small exotic mammals

Author : Lesa Thompson

Categories : Exotics, Vets

Date : September 14, 2015

They may be smaller in size than the more traditional pet dogs and cats; however, small “exotic” pets including rats and guinea pigs are popular not only with children, but also many adults.

This article will outline care of these species, as well as covering some of the more common ailments.

Care

Rats are a popular pet among both children and adults.

Rats and mice are omnivorous or herbivorous and are usually fed a commercial rodent diet with a small amount of fresh fruit and vegetables.

Hamsters are omnivorous, hoard food and are fed commercial food. As with people, guinea pigs have a daily requirement for vitamin C. Their diet is predominantly hay, with fresh vegetables and some commercial mix.

1 / 9 It is important to securely house small animals, particularly hamsters, to prevent escape – usually in a plastic enclosure with a mesh roof or, conversely, a wire cage with solid plastic base, and substrate of sawdust or wood shavings. Use shredded paper in the nest box.

Guinea pig hutches should have a solid base with wood shavings or shredded paper bedding, and also a large run area. They are usually housed in single sex groups (castrating males), pairs or harems, with a hide area for each animal.

Chinchillas are usually housed in multilevel enclosures in pairs, single sex groups or harems. Enclosures are usually wire mesh with wooden shelves and a nest box. They are adapted to low humidity and cooler temperatures, and require a short dust bath daily to aid fur condition.

Table 1 outlines the biology of these exotic small animals.

Table 1. Biology of small mammals

Consultation

Since many ailments may be related to husbandry issues, a thorough history should include details of the patient’s husbandry conditions. Clinical examination should be performed gently, but while securely restraining the animal; it may be useful to have an experienced nurse hold the animal while conducting the examination. It is vital to obtain an accurate bodyweight prior to calculating doses for treatments – use a set of small digital scales.

It is useful to consider the animal’s needs carefully before hospitalisation. For example, provide water in a recognisable container – usually a sipper bottle, although, in some cases, a bowl may be used (if in doubt, provide both). To reduce stress, house these animals in an area away from the sights and smells of predator species such as dogs, cats and ferrets.

2 / 9 If the patient is in poor condition and/or not self-feeding, supplemental fluid and nutrition needs should also be considered. Debilitated animals may benefit from gentle warming, oxygen therapy (provide as an oxygen tent around the whole enclosure rather than restraining the patient) and/or fluid therapy (such as subcutaneous injection of fluids warmed to body temperature) as appropriate before more invasive investigation and treatment procedures are performed.

Common ailments

Digestive tract disorders

Restraint of a Roborovski hamster to examine the ventrum and incisors.

Each of the species has differing gastrointestinal anatomy and physiology, adapted to different diets. In many cases presented, initial treatment is required while a diagnosis is being made – providing analgesia (pain reduces appetite), fluids and electrolytes, correcting motility disorders, regulating temperature (usually via external heat sources to hypothermic patients) and nutritional support. If gastric dilatation or tympany is present, it requires treatment by passing a stomach tube or by paracentesis.

3 / 9 Facial swellings in hamsters may be due to cheek pouch disease. In all the species discussed, dental disease should be considered as a primary cause of perioral swelling, altered appetite or other gastrointestinal problems in small mammals. Other clinical signs of dental disease are hypersalivation, weight loss and reduced fur quality due to lack of grooming.

Examination of cheek teeth (Table 2) usually requires sedation or general anaesthesia, with radiography to confirm the extent of pathology present. Adjustment of crown height can be performed using a high speed or low speed dental unit with a straight hand piece – never clip teeth as resulting vertical fractures or torsion are common.

Table 2. Dentition in small mammals

Treatment of infection associated with periodontal disease is difficult, often requiring surgery and prolonged medication.

Sudden diet changes or stresses may result in diarrhoea. Infectious causes include:

bacteria (for example, Tyzzer’s disease caused by Clostridium piliforme, Salmonella species, Escherichia coli, Helicobacter species and, significantly in hamsters, Lawsonia intracellularis) viruses (such as corona-viruses in rats and mouse Rotavirus) parasites (mostly coccidia; protozoa, cestodes and helminths usually cause no clinical signs) yeast (Candida albicans)

As in other species, young animals are the most susceptible to infections, particularly around the time of weaning. Hepatic lipidosis may result in anorexia – especially in obese, pregnant or lactating females. Antibiotics may result in colitis, due to Clostridium difficile enterotoxaemia and/or E coli overgrowth.

Respiratory disease

Infectious respiratory disease is relatively common in small mammals, most frequently caused by Mycoplasma pulmonis in rats and mice, and Bordetella bronchiseptica in guinea pigs. Subclinical

4 / 9 infections may become a problem in suboptimal husbandry conditions or concurrent with other disease processes.

Note, in rats, red/brown staining around the eyes and nose is most likely porphyrin and a sign of general illness, rather than a specific sign of ocular or respiratory disease. Diagnosis may require use of techniques such as deep nasal swabs and radiography. Treatment can include oxygen therapy, nebulisation with a range of agents (such as mucolytics, bronchodilators and antimicrobials) and oral/parenteral medication (including antimicrobials and analgesia as necessary).

Cardiovascular problems

Cardiovascular disease has been reported in chinchillas and hamsters. Treatments suggested to treat cases with clinical signs include diuretics, digoxin and angiotensin-converting enzyme inhibitors.

Urogenital conditions

5 / 9 Skull and mandible sets from chinchillas with normal teeth (top) and with dental disease (bottom).

Clinical signs of urogenital problems may be vague – such as appetite loss or cachexia – or more specific, such as polydipsia or polyuria. During case investigation, haematuria should be distinguished from haemorrhage originating from the reproductive system.

Urinalysis, blood chemistry and imaging can be used. The most common uropathy seen in guinea pigs and chinchillas is obstruction due to urolithiasis; other urinary tract diseases include bacterial and viral infections, and nephropathies (particularly in old rats). In cases of renal dysfunction, provide hydration, a low-protein diet and supportive care.

Reproductive disorders

Endometritis and pyometra are seen in small mammals. Mammary tumours are common in both male and female rats – these are usually benign and non-invasive, but can become large. Cystic ovarian disease in guinea pigs is relatively common in 18-month-old to five-year-old females. A differential diagnosis is ovarian neoplasia. Medical treatment options for cystic ovaries include percutaneous fine-needle aspiration and hormone therapy (such as leuprolide acetate or gonadotrophin-releasing hormone), but the treatment of choice is ovariohysterectomy.

This species may have dystocia due to many causes, such as obesity and uterine inertia. A peculiarity of guinea pigs is fusion of the pelvic symphysis at six months old to eight months old, meaning dystocia is more likely in animals first bred after six months of age. Pregnancy toxaemia is also common prepartum in guinea pigs, necessitating prompt treatment (intravenous fluid therapy

6 / 9 supplemented with dextrose, calcium gluconate and – if hypertension is present – caesarean section).

Dermatological disease

Skin conditions may be due to several aetiologies: bacterial, fungal or viral infection; ectoparasites or endoparasites; neoplasia; and nutritional, environmental or behavioural diseases. Investigation is similar to other species, with sample collection such as tape strips, skin scrapes, hair plucks and skin biopsy. Concomitant disease is frequently found, often associated with immunosuppression (for example, fur mites or bacterial infection are often secondary to other conditions) and all aspects should be addressed.

Of specific note are environment-related disease such as ringtail caused by low humidity or poor coat condition in excessively high humidity, and behavioural disease such as barbering or bite wounds seen in groups with overcrowding or stress. Many of the small mammal species are susceptible to ulcerative pododermatitis – particularly guinea pigs – and treatment involves both medical therapies and correction of any husbandry problems. Early hypovitaminosis C in guinea pigs may present with coat and skin signs. Bilaterally symmetrical non-pruritic alopecia in this species may also be due to cystic ovarian disease or endocrine disease. Rough handling of chinchillas may result in “fur slip”. Their fine hair may also lead to formation of “fur rings” around the penis in male chinchillas.

Neoplasia

Mammary neoplasia in mice is usually malignant carcinoma/adenocarcinoma, while in rats it is usually benign fibroadenoma. Note, mammary tissue extends from the axillary to inguinal regions, and resulting tumours can become large enough to impair mobility. Skin neoplasias in hamsters are usually a form of lymphoma (such as transmissible lymphoma caused by hamster polyomavirus infection or epitheliotrophic lymphoma) and carry a poor prognosis. In guinea pigs, most cutaneous tumours are benign trichoepithelioma.

Neurological and musculoskeletal disorders

7 / 9 Auscultation of a guinea pig.

Ulcerative pododermatitis in guinea pigs is often associated with Staphylococcus aureus infection. Osteoarthritis may be associated with this condition in guinea pigs, but is also seen alone in aged rats and mice. Trauma from falls or accidental crushing may cause fractures. Hypovitaminosis C in guinea pigs may manifest as lameness or a stiff gait, along with vocalisation due to pain when handled. Guinea pigs and chinchillas in particular are susceptible to heat stress, resulting in collapse.

Head tilts are not uncommon in small mammals. In older rats, these may be due to pituitary hyperplasia and adenomas. In both rats and mice, M pulmonis respiratory infection may progress to cause otitis media or interna. Otitis media is often associated with pneumonia in guinea pigs. In young chinchillas, otitis media may spread to result in meningoencephalitis.

Ophthalmic disease

Ophthalmic conditions may be primarily ocular in origin (for example, congenital disorders, corneal ulcers, irritation from fumes or dust, keratoconjunctivitis sicca or neoplasia), but are frequently associated with other conditions (for example, respiratory disease, spread of infection from the skin or dental disease). A complete physical examination is therefore necessary in patients presenting with ocular signs.

Conclusion

As with other exotic pet species, many problems originate, or are exacerbated, by suboptimal husbandry.

To treat these animals and enable them to live healthy lives, it is therefore vital to not only provide

8 / 9 appropriate medical and surgical treatments for the patients, but also supply owners with the knowledge to care for their pets in the best manner possible.