Ear tag induced Staphylococcus infection in mice.

Mice used in a 2-year oral toxicity study developed a progressive, moist dermatitis. The initial lesions were seen around the ears in which metal identification tags had been placed and usually progressed to include the skin of the neck and shoulder. Clinically, the mice were pruritic, lost weight, had rough coats, and became moribund. The predominant finding at necropsy was pale brown kidneys with irregular granular surfaces. Histologically, there was inflammation and focal-to-diffuse necrosis in the visceral organs and affected skin. The predominant organism isolated from the skin, kidneys and heart blood was Staphylococcus aureus. This bacterium is a common inhabitant of the skin of conventionally housed mice and its isolation from the kidneys and blood suggested that the portal of entry was the wound caused by the insertion of the metal ear tag.

Spontaneous disseminated cytomegalic inclusion disease in an ageing laboratory mouse.

An untreated C57BL/6NCrlBR male mouse in a life-long longevity study, killed in extremis at 761 days of age, had mild focal necrotic hepatitis and extensive focal necrotic adrenalitis. Characteristic cytomegalic cells bearing intranuclear and cytoplasmic inclusions and cytoplasmic vacuoles were seen in necrotic areas. Scattered intranuclear inclusions were also seen in the reticulum cells of the spleen and acinar epithelium of the submaxillary glands. We believe this to be the first report of spontaneous disseminated cytomegalic inclusion disease in aged mice.