Issues

Mastitis

 

• Bacterial infection of one or more lactating glands.
• Result of ascending infection, trauma to the gland, or hematogenous spread.
• Escherichia coli, Staphylococci, and β-hemolytic streptococci—most commonly involved. Mycobacterium and blastomycosis reported.
• Potentially life-threatening infection; may lead to septic shock.
• Sepsis—direct effect of mammary glands with systemic involvement.

 

SIGNALMENT

• Postpartum bitch and queen
• Pseudopregnant lactating bitch or queen (rare)

 

SIGNS

Historical Findings

• Anorexia
• Lethargy
• Neglect of puppies or kittens
• Failure of puppies or kittens to thrive
• Physical Examination Findings
• Firm, swollen, warm, and painful mammary gland(s) from which purulent or hemorrhagic fluid can be expressed.
• Fever, dehydration, and septic shock—with systemic involvement.
• Abscessation or gangrene of gland(s) can result.

 

CAUSES & RISK FACTORS

• Ascending infection via teat canals.
• Trauma inflicted by puppy or kitten toenails and teeth.
• Poor hygiene.
• Systemic infection originating elsewhere (e.g., metritis).
• Rarely secondary to fibroadenomatous hyperplasia in queens.

 

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

• Galactostasis—no systemic illness; cytologic examination and culture of milk help with differentiation.
• Inflammatory mammary adenocarcinoma—affected gland does not produce milk; differentiated by biopsy.

 

CBC/BIOCHEMISTRY/URINALYSIS

• Leukocytosis with left shift
• Leukopenia—with sepsis
• Mildly high PCV, total protein, and BUN—with dehydration

 

IMAGING

• Ultrasonography reveals loss of distinct layering of normal tissue in glands, decreased echogenicity, increased heterogeneity, and altered blood vessel density on color Doppler.
• Color Doppler can assist in prognosis—loss of blood vessels in inflamed areas predicts progression to gangrene.

 

OTHER LABORATORY TESTS

Culture—identification and sensitivity of microorganisms from milk of affected glands; screening for methicillin-resistant Staphylococcus aureus recommended.

 

DIAGNOSTIC PROCEDURES

• pH of milk—normally slightly more acidic than serum, may become alkaline with infection.
• Cytology—neutrophils, macrophages, and other mononuclear cells can be observed in normal milk; the presence of large numbers of free and phagocytosed bacteria and degenerative neutrophils is noted with septic disease; bacterial culture to identify the organism and sensitivity pattern.

 

TREATMENT

• Inpatient until stable.
• Puppies and kittens—neonates may be allowed to continue nursing unless glands are necrotic or dam is systemically ill; affects choice of antibiotics; monitor weight gain in neonates: pups should gain 10% of birth weight per day, kittens should gain a minimum of 7–10 g/day.
• Dehydration or sepsis—intravenous fluid therapy.
• Correct electrolyte imbalances and hypoglycemia.
• Treat shock, if present.
• Apply warm compress and milk out affected gland(s) several times daily.
• Cover glands with friable tissue to prevent excoriation if nursing is allowed.
• Application of cabbage leaf wraps to affected glands may speed resolution.
• Abscessed or gangrenous glands—require surgical debridement, with or without negative pressure wound therapy.
• Open wound management may be needed after surgery in some cases; negative pressure wound therapy useful adjunctive modality postoperatively and for conservatively managed cases.

MEDICATIONS

DRUG(S)

Acidic milk—weak bases; erythromycin (10 mg/kg PO q8h), lincomycin (15 mg/kg PO q8h), or trimethoprim-sulphadiazine (15–30 mg/kg PO q12h), for 21 days.

Alkaline milk—weak acids; amoxicillin or cephalosporin (20 mg/kg q8h, dogs and cats); amoxicillin/clavulanic acid (13.75 mg/kg PO q12h, dogs; 62.5 mg/cat PO q12h, cats) for 21 days.

Either alkaline or acidic milk—chloramphenicol (40–50 mg/kg PO q8h) or enrofloxacin (2.5 mg/kg PO q12h) for 21 days.

May infuse affected gland(s) with 1% betadine solution by lacrimal cannula.

Cabergoline (5 μg/kg PO q24h, 5–7 days) to suppress lactation in unaffected glands in patients with sepsis; neonates must be hand reared.

 

CONTRAINDICATIONS/POSSIBLE INTERACTIONS

Patient allowed to nurse—avoid tetracycline, enrofloxacin, and chloramphenicol; may use cephalosporins, amoxicillin, and amoxicillin with clavulanic acid.

 

FOLLOW-UP

PATIENT MONITORING

• Physical examination and CBC.
• Repeated ultrasonographic evaluation helps assess healing—normal distinct layering of tissues will appear with recovery.

 

PREVENTION/AVOIDANCE

• Clean environment
• Hair shaved from around mammary glands
• Toenails of puppies and kittens clipped
• Ensure neonates nurse from all glands.

POSSIBLE COMPLICATIONS

• Abscessation or gangrene—may cause loss of gland(s).
• Hand-raising puppies and kittens—requires considerable commitment by the owner, may affect behavioral outcome of offspring.

 

EXPECTED COURSE AND PROGNOSIS

Prognosis—good with treatment

 

MISCELLANEOUS

ABBREVIATION

PCV = packed cell volume

 

Visit your veterinarian as early recognition, diagnosis, and treatment are essential.

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