Dog: Mastitis

General information

Other common/scientific names: infection of the mammary glands

A female dog normally has five mammary glands on both sides of the abdomen, commonly referred to as the mammary chain. Each gland has its own nipple. Mastitis is defined as inflammation of the mammary glands.


Mastitis in dogs is usually caused by a bacterial infection. The bacteria E. coli, Staphylococcus spp and Streptococcus spp are commonly implicated.


Inflammation and resulting infection of the mammary tissue can occur from unsanitary conditions, trauma from nursing puppies, trauma from a false pregnancy and/or an ascending infection through the nipple.

Cardinal symptom

Swollen mammary glands


One or more mammary glands are swollen, painful and red. The glands may be ulcerated and become abscessed. The milk may be discolored. Dogs with systemic illness may develop a fever, decreased appetite, listlessness and vomiting. Puppies may become weak, cry excessively and die.


Diagnosis of mastitis is made by physical examination. The milk can be submitted for a culture and sensitivity to identify the infection and appropriate antibiotic. In severe cases, bloodwork consisting of a complete blood count (CBC) and serum biochemistry may be necessary to support the diagnosis and give an indication of the severity of the condition.


Antibiotics are used to treat mastitis and should be administered when mastitis is diagnosed. Results of the culture and sensitivity testing may require a change in the antibiotic. Alternating hot and cold packs can reduce the inflammation of the glands. Abscessed glands may need to be lanced and debrided. In severe cases, the female may need to be placed on intravenous fluids for supportive care.

Whether the pups should nurse from the infected glands is controversial. Puppies should not be allowed to nurse from abscessed glands. If the pups are not allowed to nurse, the mammary glands should be drained of the milk twice daily. Allowing the pups to nurse will keep the glands milked out and maintain the maternal-puppy contact. Pups that are not allowed to nurse will need to be bottle fed with milk replacer several times a day.


Most females recover completely from mastitis. However, good nursing care of both the bitch and the puppies is needed to prevent the pups from becoming weak and dying.

Update version: 4/24/2014, © Copyright by
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