Mastitis in Dogs


Overview of Canine Mastitis

Mastitis is a bacterial infection of the mammary glands, almost exclusively seen in females. It may occur in one or multiple glands and usually occurs in lactating dogs. It is a fairly uncommon condition, but occurs more frequently in bitches (female dogs) than in queens (female cats).

Mastitis is most commonly caused by an ascending infection from the teat opening. Other potential causes or contributing factors include trauma (from nursing puppies) and hematogenous spread (infections spread via the blood). It may be more common in older dogs and in dog breeds with short legs in which trauma to the mammary glands is more likely. Poor hygiene can also be a contributing factor.

Mastitis can be a painful condition that usually is fairly localized, although some animals may become systemically ill or even septic (bacterial infection in the blood).

What to Watch For

Symptoms of Mastitis in Dogs may include: 

  • Swellings in one or more mammary glands
  • Enlarged teats
  • Redness
  • Purulent or discolored milk or discharge from glands
  • Painful mammary glands
  • Glands may abscess
  • Lethargy
  • Loss of appetite
  • Crying puppies
  • Sick or dying newborns
  • Fever in some pets
  • Diagnosis of Mastitis in Dogs

    A good history and complete physical exam are very important in establishing the appropriate order of diagnostics. The diagnosis is sometimes made on this basis alone. Additional tests may include:

  • Fluid analysis with microscopic evaluation of the milk or any discharge
  • Aspirate (inserting a needle and syringe to remove a sample of material) and cytology of solitary masses
  • Bacterial culture and sensitivity of the fluid
  • Complete blood count (CBC)

    In cases of significant systemic illness the following may be recommended:

  • A biochemical profile
  • Urinalysis
  • Chest and abdominal radiographs (X-rays)
  • Blood cultures
  • Treatment of Mastitis in Dogs

  • Systemic antibiotic therapy
  • Topical warm water compresses
  • Affected glands should be emptied
  • Glands may need to be surgically lanced or drained.
  • Severely or chronically affected glands may need to be removed (mastectomy)
  • If systemically ill or septic, intravenous fluids would be necessary
  • Home Care and Prevention

    If glands are still draining, additional warm water compresses will be required. Nursing puppies may, or may not, need to be weaned but they often require additional nutritional supplementation.

    Since mastitis is most often associated with nursing, not allowing your pet to breed is a good preventative measure. The best preventative measure is to have your pet spayed before her first heat.

    If you are breeding your pet, make sure that the bedding and surroundings are routinely kept clean. If your pet is lactating, observe the teats daily for any signs of redness, pain or abnormal swellings and discharge.       

    In-depth Information on Mastitis in Dogs

    Mastitis is almost always associated with lactating nursing animals. Trauma, poor sanitary conditions, and underling illnesses are potential predisposing factors. Most of the time, mastitis is not an emergency situation, and animals affected are not significantly ill. The only sign might be a bitch refusing to let the puppies nurse. This may be taken as a sign of the mother just being immature or uncaring. The mammary glands should always be observed closely if this is occurring.

    Mastitis is usually an acute (sudden) condition. If it is left unnoticed, an animal is immunocompromised or a particularly pathogenic (causing significant disease) bacteria is present, the infection can spread to other glands. Occasionally it may cause septicemia (bacterial blood infection). These animals are usually quite ill and require much more intensive care.

    Mammary glands may become so inflamed that they may be abscessed or even gangrenous. These conditions require surgical intervention. As apposed to abscessed glands, gangrenous glands have lost their blood supply and are cool, darker and sometimes ulcerated.

    Nursing puppies may be in poor nutritional condition due to a lack of nursing allowed (from pain experienced by the dam during nursing) or poor nutritional content of the infected milk. The nursing on infected glands itself generally is not detrimental to the animal.

    Disorders that can cause clinical signs similar to mastitis include:

  • Mammary gland enlargement caused by advanced pregnancy, lactation or pseudopregnancy. Sometimes there is an excessive accumulation (galactostasis) of milk in the glands, and they may become warm and somewhat painful.
  • Mammary fibroepithelial hypertrophy is a benign growth of the mammary tissue causing a firm swelling. The swellings may become extremely large.
  • Mammary gland tumors are fairly common and usually occur in older animals. They may occasionally be confused with mastitis especially if they are ulcerated.
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