30 Lymphoma in a hamster
Alopecia, coat abnormalities and skin problems are non-specific and common presentations of hamsters in general practice. Often, these pets belong to children and are brought to the surgery only after clinical signs of illness have been present for some time.
In the past, it has often been the case that these pets are euthanized without further diagnostics due to a combination of welfare issues, short lifespan, financial considerations and a poor prognosis. This case discussion aims to challenge that approach, and where appropriate will try to encourage investigation, accurate diagnosis and even specific treatment of these sick hamsters.
As mentioned with the other exotics cases, a thorough history is an important first step in reaching an accurate diagnosis. Sometimes this can be challenging in the small mammals. Hamsters are predominantly nocturnal so are not normally seen at their most active; also, food is often taken and buried, so food intake may not correlate with the amount being fed. Because hamsters are often children’s pets, it may be better to ask the child about the husbandry, remembering to ask carefully and sympathetically, since they are likely to be worried by what you are going to suggest.
The hamster was a gift from a family friend (who had their own litter of hamsters) approximately 15 months ago. He was housed in a large plastic hamster cage with several ‘add-on’ tubes and tunnels. The substrate was sawdust, with some shredded paper for bedding material. Its diet was a standard commercial hamster mix, with some fruit and vegetable treats provided fresh daily. He was handled frequently by the family, seemed bright and alert, and was acting normally. The patient had a 3-week history of hair loss with some pruritus, mainly affecting the back and head. Otherwise, the hamster was reported to be well; no change in thirst or appetite had been noted.
Dermatological examination revealed generalised erythema with multifocal areas of alopecia over the head and dorsum (Figs 30.1 and 30.2). There was also increased scaling of the skin in many areas. In addition, some erosions and excoriations were present on the face (Fig. 30.3).
(Courtesy of N. Perrins.)
Alopecia and rough hair coat are non-specific signs associated with multiple disease and husbandry problems. Chronic, non-pruritic, generalized alopecia with scaling and crusting around the ears and feet can be associated with any of the differential diagnoses listed above. Hairlessness can even have a hereditary predisposition. Therefore, diagnosis is important to provide the right treatment. Some of the other main differential diagnoses are considered briefly here:
Demodex is the most common ectoparasite of hamsters. They are susceptible to five different species, with D. aurati (in hair follicles) and D. criceti (in keratin and pits of the epidermal surface) being the most common (Fig. 30.4). Approximately 50% of hamsters may be asymptomatic carriers, so demonstration of mites in scrapings from healthy skin does not necessarily indicate disease. Clinical signs of demodicosis include alopecia, hyperkeratinization and scaling over the back, legs and abdomen. Pruritus is not usually a feature unless the infestation is complicated with a secondary infection. The presence of clinical signs invariably suggests an underlying disease, immunosuppression, stress or ageing. Diagnosis is made with skin scrapes, examined with light microscopy. The most effective treatment is amitraz (Aludex; Intervet) diluted to 100 ppm once weekly until 4 weeks after negative skin scrapes, although toxicity is a risk due to their small size and the difficulty of preventing grooming. Ivermectin injections (Panomec; Meriel) are useful (0.4 mg/kg subcutaneously) but will need repeating three or four times, or there is topical ivermectin (Xeno 450; Genetrix).
This is relatively uncommon in the UK, but hamsters can be clinically affected, or asymptomatic carriers. The most common dermatophytes isolated are usually Trichophyton mentagrophytes or sometimes Microsporum canis; therefore, the disease is potentially zoonotic. Clinical signs include dry circular alopecic skin lesions, usually affecting the thoracic and abdominal areas, with the clinical disease often complicated by pyoderma. Diagnosis is made with standard fungal culture techniques (see the guinea-pig case in Chapter 10). Treatment is also very similar to other pets, although it can be challenging to stop the hamster licking after using topical antifungal drugs. Regular cleaning of the cage and use of proper bedding (avoid wood shavings – e.g. allergic dermatitis attributed to pine or cedar wood shavings has been reported) helps prevent this disease.
Staphylococcal pyoderma (primary or secondary) is relatively common in hamsters. Lesions include moist dermatitis, ulcerated sores and abscesses. Treatment includes correcting any husbandry problems, replacing any abrasive bedding material with newspaper and/or paper towels, and removal of any aggressive animals. Antibiotics should be selected based on culture and sensitivity, and restricted to those safe to use in hamsters. Enrofloxacin or marbofloxacin should be effective, but penicillins, cephalosporins and aminoglycosides should be avoided. Even some trimethoprim–sulpha combinations have been associated with death in hamsters.
Hyperadrenocorticism may be caused by hyperplasia, adenomas or carcinomas of the adrenal glands. It is more common in male hamsters and generally occurs in older animals. Clinical signs include bilateral and symmetrical alopecia, hyperpigmentation and thinning of the skin, polyuria, polydipsia and polyphagia. Whenever possible, diagnosis is made by demonstrating elevated plasma cortisol levels (normal range 13.8–27.6 nmol/l). Treatment is often not attempted, but metyrapone (8 mg orally once daily for 4 weeks) was effective in one hamster.