The Classic Comprehensive Handbook of Cat Care
What to Do When Your Cat Is Sick: MASTITIS
Mastitis is an inflammation of one or more of the mammary glands (breasts) in female cats. While it may be due to abnormal drainage of milk from the gland or to trauma, it is usually caused by bacterial infection.
Affected glands look enlarged, may be discolored (red, purplish, or blue), and often feel hard and warm. They are often painful, making the female reluctant to let her kittens nurse. If you express some milk from the affected gland, it may be blood streaked, pink, gray, or brown. Often, however, the milk does not look unusual to the unaided eye. If left untreated, the gland may abscess or the female may develop more generalized signs of illness such as depression, loss of appetite, and/or fever.
In order to prevent sick kittens, do not allow them to nurse from infected glands. Placing a piece of adhesive tape over the nipple of the gland will usually effectively prevent nursing. Affected glands should be milked out three to four times a day. Ask your veterinarian to show you how to do this properly. Warm packs applied to the gland seem to relieve discomfort and speed localization of infection. Infected glands must be treated with antibiotics. Your veterinarian can culture the milk so the offending bacteria can be identified and will prescribe the appropriate antibiotic.