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Bacterial Infection of the Breast in Dogs

Mastitis in Dogs

Mastitis is a bacterial infection of one or more lactating (milk producing) glands in the breasts. It is often the result of an ascending infection, trauma to the lactating gland, or an infection that has been spread through the blood stream.

Escherichia coli (E. coli), Staphylococci, and β-hemolytic Streptococci are some of the main bacteria that are found to be most commonly involved. It is a potentially life-threatening infection, in some cases leading to septic shock, the direct effect of the mammary glands with systemic involvement.

This condition mainly affects postpartum bitches, but it rarely occurs in pseudopregnant lactating bitches too.

Symptoms and Types

  • Loss of appetite
  • Lethargy
  • Firm, swollen, warm, and painful mammary gland(s) from which purulent (pus-like) or hemorrhagic fluid can be expressed
  • Neglect of puppies (due to pain when attempting to nurse)
  • Failure of puppies to thrive
  • Fever, dehydration, and septic shock with systemic involvement
  • Abscesses or gangrene of gland(s), if left untreated


  • Ascending infection via teat canals
  • Trauma inflicted on the mammary glands by a puppy's toenails or teeth
  • Poor hygiene
  • Systemic infection originating elsewhere in the body


You will need to give a thorough history of your dog's health, onset of symptoms, and possible incidents that might have led to this condition. A complete blood profile is then typically recommended, including a chemical blood profile, a complete blood count, and a urinalysis.

If the is present, the milk is normally slightly more acidic than the serum is; it may also have increased alkalinity with infection. Neutrophils, macrophages, and other mononuclear cells can be normally observed in high numbers in normal milk; however, the presence of large numbers of free bacteria and degenerative neutrophils are noted with the presence of septic disease.

Meanwhile, if there is cancer present in the breast, the affected glands will not produce milk. Differentiation between malignant and benign condition will be achieved with an examination and culture of the mother's milk.


Anything that contains pus


The prediction of a disease’s outcome in advance


The period that immediately comes after the birthing process


A product made of fluid, cell waste, and cells


Something that is related to the whole body and not just one particular part or organ


An in-depth examination of the properties of urine; used to determine the presence or absence of illness


A nipple, as in on ruminants and equine animals


An infection of the udder; may be infectious or not


A medical condition; the contamination of a living thing by a harmful type of bacteria

mammary glands

The glands in female animals that are used to produce milk; also called the udder or breast


A passage in the body with walls


A medical condition in which the body has lost fluid or water in excessive amounts


A female dog that has not been spayed.


Necrosis of a body part that can be attributed to poor circulation


The removal and destruction of red blood cells


Something that becomes worse or life threatening as it spreads


Low amounts of glucose in the blood


Not being able to cause harm; the opposite of malignant.