Contributors: Joseph Harari, Carlos Pinto

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Cause: usually ascending bacterial (Staphyloccus aureus, Escherichia coli, etc) infection through nipple during nursing (may be hematogenous or lymphogenous) - predisposed or exacerbated by trauma, unsanitary conditions.
  • Signs: one or more mammary glands that are hot, eliciting signs of pain at touch or when trying to nurse, with purulent or blood-tinged mammary secretions; pyrexia, anorexia; puppies may be unable to feed - restless, cry, appear bloated or fail to thrive. At early stages of infection, it may be subclinical with only galactostasis of affected glands.
  • Diagnosis: clinical signs; milk cytology showing degenerate neutrophils and bacteria; complete blood count may reveal neutrophilic leukocytosis with left shift.
  • Treatment: systemic antibiotics, application of cold compresses to affected mammary glands; may need to wean pups or feed artificially until infection controlled.
  • Prognosis: good with prompt treatment.
Print off the owner factsheet Mastitis (inflammation of the mammary glands) to give to your client.

Presenting Signs

  • Lactating bitch.
  • Hot mammary glands, painful to touch.
  • Purulent mammary secretions.
  • Pups unable to feed - restless, crying and may appear bloated.



Predisposing Factors


  • Dam and puppies under unsanitary conditions in nursing box. 
  • Ascending bacterial infection predisposed by: 
    • Constant nursing in dams with large litters.  
    • Secondary galactostasis in dams nursing small litters. 


  • Ascending bacterial infection through nipple during nursing.
  • May be hematogenous or lymphogenous spread, eg metritis Acute metritis.


Presenting Problems

  • Swollen, painful mammary glands.

Client History

  • Nursing bitch.
  • Anorexia.
  • Depression.
  • Pups restless.

Clinical Signs

  • Hot mammary glands, painful to touch.
  • Purulent mammary secretions.
  • Pups unable to feed - restless, cry, may appear bloated.
  • Pyrexia Pyrexia: overview.

Diagnostic Investigation


  • Decreased echogenicity of inflamed glands, acoustic enhancement denoting discrete intercellular fluid accumulation or abscess formation. 



  • Milk sample - culture and sensitivity.
  • E. coliStaphylococcus spp or Streptococcus spp most commonly present.


  • Examination of milk sample shows neutrophils (with intracellular bacteria)/red blood cells.

Definitive diagnostic features

  • History and clinical signs.
  • Bacteriological culture and sensitivity results Bacteriology.

Differential Diagnosis

  • Excessive milk production and lack of feeding leading to milk pooling in mammary glands (galactostasis).
  • Mammary neoplasia Mammary gland: neoplasia.


Initial Symptomatic Treatment

  • Start antibiotic therapy with drugs considered safe for dam and puppies; eg broad spectrum beta-lactam antibiotics Therapeutics: antimicrobial drug, eg amoxicillin Amoxicillin/clavulanic acid Clavulanate or cephalexin Cefalexin.
  • Modify antibiotic therapy based on culture results and evaluation of milk pH.
  • Remove pups until therapy instigated.
  • Suppress lactation by administration of cabergoline Cabergoline.
  • Wean, feed artificially - this is controversial, some authors recommend nursing to empty gland.
  • Most milk secretions from mastitis are alkaline, which favor the distribution of weakly acidic drugs such as ampicillin Ampicillin or cephalosporins.
  • Distribution of weakly alkaline drugs such as trimethoprim sulfa Trimethoprim , erythromycin Erythromycin may be compromised if the pH is > 7.4.

Standard Treatment

  • Remove pups - may need to wean/feed artificially until infection controlled.
  • Suppress lactation by administration of cabergoline Cabergoline.
  • Appropriate antibiotic therapy ideally according to milk culture and sensitivity results.
  • Cold and hot packing of affected glands.
  • Surgical drainage Drain: surgical wounds, or mastectomy Mastectomy, of abscesses/debridement of gangrenous areas as necessary Mastitis: abscessated mammary tissue 01 Mastitis: abscessated mammary tissue 02.
  • Antiseptic infusions into gangrenous or abscessed glands.


  • Septicemic animals require IV fluids, antibiotics.
  • Puppies weaned need good husbandry techniques.


Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Vasiu I, Dabrowski R, Tvarijonaviciute A (2021) Lactation-related mammary gland pathologies-A neglected emergency in the bitch. Reprod Domest Anim 56 (2), 208-230 PubMed.
  • Gonzales K (2018) Periparturient diseases in the dam. Vet Clin North Am Small Anim Pract 48 (4), 663-681 PubMed.
  • Hasegawa T et al (1993) Platelet abnormalities in dog suffering from gangrenous mastitis by Staphylococcus aureus infection. J Vet Med Sci 55 (1), 169-171 PubMed.
  • Dernell W S, Kreeger J (1992) Peracute, necrotizing mastitis as a cause of fatal septicemia and endotoxemia in a dog. Canine Pract 17 (6), 25-29 VetMedResource.
  • Johnson C A (1986) Non-neoplastic disorders of the mammary gland. Vet Clin North Am Small Anim Pract 16 (3), 539-542 PubMed.
  • Smith F O (1986) Post partum diseases. Vet Clin North Am Small Anim Pract 16 (3), 521-524 PubMed.

Other Sources of Information