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Care and common ailments of small exotic mammals
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.
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
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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.
If the patient is in poor condition and/or not self-feeding, supplemental fluid and nutrition needs
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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.
Facial swellings in hamsters may be due to cheek pouch disease. In all the species discussed,
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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
infections may become a problem in suboptimal husbandry conditions or concurrent with other
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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
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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
supplemented with dextrose, calcium gluconate and – if hypertension is present – caesarean
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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
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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
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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.
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