Skin Diseases of Rodents

MICE

Fur mites can cause pruritus, alopecia and selftrauma. Treatment is with ivermectin or selamectin. Secondary bacterial dermatitis and abscesses as a result of self-trauma or fight wounds are commonly seen. Trichophyton mentagrophytes can cause hair loss and well-demarcated crusty lesions. Treatment is with oral griseofulvin or enilconazole wash. Cutaneous neoplasia is rare but squamous cell carcinoma occurs most frequently. Barbering is common in groups, especially males, where the dominant mouse chews the hair of sub-ordinates without causing skin damage. Treatment is by reducing stocking density and enriching the environment. Low environmental humidity (<20%) can cause “ring-tail”, where one or more annular constrictions of the tail can cause oedema andnecrosis.

RATS

Radfordia ensifera (rat fur mite) causes pruritus and self-trauma. Notoedres muris causes warty, papular lesions on the pinnae, nose and tail.. Other rarer mites are Ornithonyssus bacoti, Sarcoptes scabiei, Trixacarus diversus, Trixacarus caviae, Myobia musculi and Demodex sp. Polyplax spinulosa the spined rat louse, is rarely found in pet rats but can cause pruritus, dermatitis and anaemia, especially in young or debilitated animals. Treatment is ivermectin or topical fipronil or selamectin. Staphylococcus aureus can cause an ulcerative dermatitis and can lead to severe self-mutilation. Obesity, poor cage hygiene or wire mesh floors can lead to ulcerative pododermatitis. Dermatophytosis is rare. Cutaneous neoplasia is also rare, but almost all types have been reported. Squamous cell carcinomas and papillomas are the most common. Barbering is uncommon but fight wounds can occur between adult males. The fur of aged male albino rats becomes yellow and coarse due to increased sebaceous secretions. Brown skin scales on the dorsum and tail are often seen in older males.

GERBILS

Ectoparasitic infestations are uncommon. Demodex meroni causes alopecia, scaling and focal ulcerative dermatitis. Fur mites are reported but rare. Nasal dermatitis is common, particularly in group housed animals stressed by overcrowding and high humidity levels. Small focal areas of alopecia and crusting around the nares may progress to the face, medial forelimbs and abdomen. Hypersecretion of the Harderian gland and accumulation of porphyrin pigment around the nares is irritant and leads to self-trauma and secondary staphylococcal infection. Improving husbandry, environmental temperature and humidity (< 50%) and provision of a sand bath will all help. The large ventral abdominal sebaceous gland frequently becomes inflamed and ulcerated. Early neoplastic changes appear similar. Total gland excision is recommended. Cystic ovaries are common in older females and symmetrical alopecia may be seen, Hyperadrenocorticism has been reported. Cutaneous neoplasia is relatively common, especially tumours of the ventral scent gland.. Barbering may occur if gerbils are housed in large groups. ‘Bald nose’ is associated with rubbing on wire cage feeders and cage bars. ‘Tail slip’ occurs when the tail is grasped and the skin degloves. If the relative humidity exceeds 50% gerbils will become "starey coated". [...]