Mastitis

• 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.

• Lactating bitch.
• Hot mammary glands, painful to touch.
• Purulent mammary secretions.

• Pups unable to feed - restless, crying and may appear bloated.

• Escherichia coli Escherichia coli , Staphylococcus spp Staphylococcus spp , Streptococcus spp Streptococcus spp most common.

General

• 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.

• Swollen, painful mammary glands.

• Nursing bitch.
• Anorexia.
• Depression.

• Pups restless.

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

Ultrasonography 

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

Hematology

• Neutrophilic leukocytosis with left shift Hematology: neutrophil.
• Early/severe cases may show neutropenia with degenerative left shift.
• Toxic neutrophils may also be seen Hematology: complete blood count (CBC).

Bacteriology

• Milk sample - culture and sensitivity.
• E. coli, Staphylococcus spp or Streptococcus spp most commonly present.

Cytopathology

• 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.

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

• 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.

• 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  .
• Antiseptic infusions into gangrenous or abscessed glands.

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

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.