e. In pet rodents, total blood volume is about 6% to 7% of body weight (e.g. 3 to 4 ml in a 60-g gerbil). Up to 25% of this amount can be safely collected every two weeks (ea. 0.9 ml in a 60-g gerbil). Replace blood volume subcutaneously or intraperitoneally with an equal amount of a balanced electrolyte solution.
When a pet rodent dies: Most pet rodent owners are amazed that an animal that seemed healthy the night before can be semicomatose and near death the next day. When a pet rodent dies (or an owner chooses euthanasia), offer a necropsy to ascertain the cause of death and to determine whether a zoonotic disease (e.g. salmonellosis, hymenolepiasis, lymphocytic choriomeningitis), although rare, was involved. Necropsy findings can not only comfort many owners but provide useful information for practitioners.
Differential diagnoses are based on history, clinical signs, and knowledge of conditions common to species.
Handling and physical examination
Pet rodents need special handling and restraint. Lift guinea pigs with one hand under the trunk, and one under the hindquarters. Pick up hamsters by cupping the hamster, holding loose skin at nape, or by gripping over the back. (Hamsters can turn and bite even when held by nape.) To restrain/pick up rats, mice, and gerbils, hold them either at the base of the tail or the nape. Large rats can be held by putting one hand over the back and ribcage and supporting the trunk with the other hand. Immediately release any rodent that struggles. Get an accurate weight, check teeth, and auscult with a pediatric stethoscope.
Common clinical signs
Obtain a history, perform a complete physical examination, and obtain a skin scraping/fungal culture (especially if pruritus present). Skin biopsies (use isoflurane anesthesia) may be more cost effective and diagnostic than skin scraping/fungal culture.
Common causes are mange, ringworm, bacterial dermatitis, cervical lymphadenitis, pododermatitis, lice infestation, nasal dermatitis, and skin cancer
Demodectic mange in older pet rodents usually signifies underlying internal disorder
Type of skin lesion Animals affected Diagnosis/Treatment Alopecia Hamsters, gerbils, guinea pigs Skin scraping, fungal culture, skin biopsy treat for subsequent diagnosis Scaling without pruritis Hamsters gerbils, guinea pigs Skin scraping, fungal culture, skin biopsy treat for subsequent diagnosis Scaling with pruritis Hamsters gerbils, guinea pigs Bathe with an antipruritic or mild antiseborrheic shampoo labeled for cats and/or give ivermectin (200 400m g/kg SC in two treatments 10 14 days apart). Ivermectin treatment may be diagnostic for mange if the lesions resolve. Abscesses (submandibular or cervical lymphadenitis) Guinea pigs Caused by Streptococcus zooepidemicus.
Treatment: Lance abscess or remove lymph nodes; follow with systemic antibiotics (trimethoprim-sulfamethoxazole, trimethoprim-sulfadiazine, or enrofloxacin).
Mange Guinea pigs (Demodex caviae or Trixacarus caviae, a sarcoptid mite)
Gerbils (Demodex spp.)
Hamster (Demodex spp., Notoedres notoedres, Notoedres cati)
*Trixacarus mange: whole body lime-sulfur dips (once a week continuing for 2 weeks after a negative skin scraping) or ivermectin (200 400 m g/kg SC every 10 14 days until skin scraping is negative).
*Demodectic mange: Amitraz (MitabanÒ ) (250 ppm as a whole body dip, once a week, continuing for 4 weeks after a negative skin scraping).
*Notoedric mange: whole body lime-sulfur dips (once a week continuing for 2 weeks after a negative skin scraping) or ivermectin (200 400 m g/kg SC every 10 14 days until skin scraping is negative).
**Dermatophytosis in rodents is potentially zoonotic
All pet rodents (Trichophyton mentagrophytes) Dx: Fungal culture or biopsy
Whole body treatment: 2% lime-sulfur or 1% chlorhexidine, topical application
Local lesions: use topical creams (TresadermÒ or ConofiteÒ )
Systemic treatment: Give griseofulvin 25 mg/kg PO SID until fungal culture is negative. (Use only if needed; do not use in pregnant animals.)
Bacterial dermatitis All pet rodents, especially those house