Once a bitch has had Mastitis it is more prone to it in subsequent litters.

Mastitis refers to swelling, inflammation, and infection of the of the many things that can go wrong during the pregnancy, birth, and nursing process.  Having babies is a fairly high risk venture in all species, and of all the potential problems that can occur, mastitis is usually fairly easy to treat ...but not always: this disease can be deadly.  Yet another reason to recommend spaying  female pets unless you really want a litter and are willing to take on the responsibility and expenses of when things go wrong.

Some Basics:

Think about it; the spongy glands of the breasts have been recently stimulated by hormone changes to swell and produce milk and colostrum...full of nourishing fats and sugars...A NEAR PERFECT situation for bacterial growth.  All a bacteria has to do to gain entrance into the milk enriched gland is find a way up the teat canal...which very likely might be swollen and raw from being suckled and gnawed on by greedy little infants.

If the bacteria can't make it up the nipple, it can possibly gain entrance from the blood ; after all, it's common to have an extra high bacteria count in the uterus, the vagina, and the near-by urinary tract for a few weeks after delivery...AND NOT ONLY THAT, but the mom's immune system is often out of whack during the massive hormone changes of pregnancy and nursing.  So, bacteria might gain entrance into the blood stream, evade the immune system's defenses...and settle happily into the milky goo of the mammary glands.

To top it off, the intestinal system...the number one source of bacterial invasion into the blood more likely to be raw and inflamed during nursing.  Why?  Because the hormones of pregnancy stimulate intestinal worms to come out of dormancy and feast on the intestinal tract...AND...GI upset (inflammation) is very common post delivery due to the mom eating all those nasty placentas,  cleaning up all that vaginal discharge, and licking all those puppy or kitten butts.

After reading the above, you might not be surprised to know that ALL (100%)  nursing dogs and cats get bacteria in their breast tissue.  Luckily, most of the time, the immune system is successful at keeping the bacteria numbers low enough so as not to cause obvious disease needing medical treatment.  But sometimes the immune system is not up to par...often due to poor nutrition, poor parasite control, or poor vaccination protection...and sometimes due to poor dental care. (Inflamed gums are a major source of bacterial entry into the blood stream)  Sometimes the immune system is simply over-whelmed:

This article is about what to expect if your pet happens to get an infection of the breast tissue during nursing...a disease known as MASTITIS


The most obvious symptom is a swollen mammary gland (breast, tit, etc) that is either more red, discolored, painful, firm, or lumpy than the other breasts on the pet.

The breast may discharge pus...or milk that looks different from the other breasts.

Other symptoms might include:

  • Fever (rectal temperatures greater than 103 F in both dogs and cats)
  • No or poor appetite
  • Dying pups or kittens
  • Poor energy level

Note: the above symptoms are not exclusive to mastitis; they could be caused by other or additional problems.

What to Expect When you go to the Vet:

A good exam.  It's tempting to simply look at an obviously infected breast and make

the diagnosis of mastitis...and start treatment.  But it's not that simple.  There are usually multiple problems and a good vet will go over the entire pet checking out all the major body systems to see what we're up against.  Here are some examples of problems that are often associated with gross infections of the mammary glands:

  • High fever and all the secondary vascular changes that can occur with high fevers such as blood clots.
  • Dehydration
  • Toxic Shock and Sepsis
  • Stress, bacterial invasion, and resulting dysfunction of the liver, kidney, and lymphatic systems.
  • Toxic Milk
  • Gangrene (from gas producing organisms)

Moderate to severe Intestinal upset and inflammation resulting from the fever and infection...or as mentioned in the introduction the cause of the problem.

And remember...nursing is a time when multiple problems can happen together: Milk Fever (Calcium-phosphorus imbalances), protein deficiencies, post delivery diabetes and other blood sugar irregularities, as well as immune system suppression, greatly increased parasitism, and to some extent hormone induced depression.

The take home message: a good professional exam by a veterinarian is important even though it's usually not difficult to determine that your pet has mastitis.

Lab work your vet might recommend:

As you might gather from reading the above...lab work isn't usually needed to make a diagnosis of mastitis.  But lab work might very well be needed to determine how badly the rest of the body is faring.  Also:  Many mastitis cases require anesthesia and surgical draining and debridement (cutting away of dead, putrid, and damaged tissue).  Therefore, to minimize the risk of anesthesia and surgery, your vet may recommend:

  • Blood Work:  (usually a CBC and Blood Chemistry).  These common tests flag sepsis, diabetes, anemia, kidney, liver, and pancreatic diseases, dehydration, and electrolyte problems.
  • Fluid analysis with microscopic evaluation of the milk or any discharge.  What the vet will be looking for is a high white blood cell count of the milk, free or encapsulated bacteria, and a type of white blood cell called degenerate neutrophils. Milk pH might also be considered as different antibiotics work better at differ pH levels.
  • Aspirate (inserting a needle and syringe to remove a sample of material) and cytology of solitary masses
  • Bacterial culture and sensitivity of the fluid to allow better choice of antibiotic
  • Bacterial culture of the blood if sepsis is suspected
  • Urinalysis: useful anytime a patient acts weak and sick as a screening test for dehydration, diabetes, debilitation, and kidney function.


Treatment options will depend on how sick the patient is in general and how extensive the local damage to the breast tissue.  Mastitis can be a minor, inexpensive nuisance or a major, life threatening disease requiring a big commitment.

Probable treatments will include:

  • Antibiotic injections followed by oral antibiotics
  • Some type of anti-inflammatory medication to reduce swelling.  This usually means  some sort of short acting steroid...our most effective treatment...but also one with  potential problems that needs to be monitored.
  • Topical wound cleaners, compresses, ointments, wound healing enhancers, and  various soothing remedies  (each vet seems to have their favourites)
  • Supportive care of the whole patient if needed:  IV Fluids, antioxidants, electrolytes,  pain meds, etc. Knowing when and how aggressive to get with supportive care for each different case is where experience and the practice art become so important.  Too little and the patient suffers or dies.  Too aggressive and we waste your money and lose your respect for making a mountain out of a mole hill.
  • Time to heal and good home treatment by the pet owner.  Once bacteria gets established in such a perfect growth media as a milky breast it won't be easy to kill it  off...It's critical that you administer the pet's antibiotics faithfully for at least 10 days. Even if your vet does everything right, mastitis is a potentially fatal disease and there's a fair chance that the initial medical treatment won't be entirely successful and more aggressive treatment and/or surgery will be needed.  You can greatly increase your chance of initial success by making sure you give the prescribed meds even if difficult or inconvenient to do so.
  • Clean bedding.  A pet with a draining breast shouldn't be lying on wet, urine soaked, filthy bedding.  Nor should the bedding be irritating.    Recheck/follow up exam if not obviously all better.  Some people seem to think that  the vet somehow failed if a treatment plan doesn't go perfectly.  Hey...this is a serious disease with lots of complicating factors.  A certain percentage of cases will need additional work.

Some Other Treatments or Things that your vet may consider:

  • Early weaning of the pups or kittens to allow the mammary glands to dry up or to prevent death of the babies.  Sometimes we recommend total separation (different buildings) so that the momma pet can't smell or hear their babies which stimulates lactation.  Another reason for early weaning is if the momma pet is simply too weak to both fight off her mastitis and nurse.  There are negatives to early weaning the decision will be based on each case like so many other situations in medicine.
  • Supplemental feeding of the puppies or kittens.  A sort of compromise of early weaning.
  • Shaving the hair from around the teats and clipping the toe nails of the puppies or kittens.
  • Manual milking of the infected breast to keep it draining.
  • Herbal and other "Alternative" treatments.

Caution: Disorders that might be confused with mastitis include:

  • Insect or snake bite wounds to the breasts.  This is, technically, still mastitis, but treatment would also include antihistamines etc.
  • Mammary gland enlargement caused by advanced pregnancy, lactation or pseudo-pregnancy. Sometimes there is an excessive accumulation (galactostasis) of milk in the glands, and they may become warm and somewhat painful. In other words...just because the breasts are firm and tender doesn't necessarily mean they're infected.
  • Mammary hypertrophy is a benign growth of the mammary tissue causing a firm swelling.

Mammary gland tumors are fairly common in older animals and could be confused with mastitis especially if they are draining.

Article by: Roger Ross DVM
Web Site

Normal nursing glands are soft and enlarged. Diseased glands are red, hard, and painful. In general, the bitch does not act sick; the disease is confined to the mammary tissue. The bitch may be sore and discourage the pups from nursing; however, it is important to keep the pups nursing the affected glands. This is not harmful to the puppies and helps flush out the infected material. Hot packing may be helpful.

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 animals. 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 (spread via the blood). 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:

  • Swellings in one or more mammary glands

  • Enlarged teats

  • Redness 

  • Discharge

  • Painful mammary glands

  • Lethargy

  • Loss of appetite

  • Sick or dying newborns 


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

  • 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.

By Dr. Douglas Brum 

(Inflammation of the Breasts)
Etiologic agents - coliforms, staph. strep. 

Clinical signs 
  • One or more of the mammary glands is enlarged, painful, hot, and red. 
  • The bitch is febrile 
  • The bitch may neglect the pups. 
  • The bitch may be asymptomatic in mild cases, but the pups fail to thrive. 


  • Examination of the mammary glands will reveal that they are enlarged, painful, hot, and red. 
  • The milk may be off colour. 
  • There may be a leukocytosis 


  • Perform a culture/sensitivity of milk. 
  • Treat with antibiotics that distribute to the milk. Mastitic milk is usually acidic, and bases distribute better into acidic milk. Ampicillin or oxacillin are good choices until a culture and sensitivity results are back.
  • Acute Mastitis Bitch without nursing pups
  • Aerobic bacteria 
  • Gram-negative infection - Broad-spectrum cephalosporin (second- or third-generation), quinolones, chloramphenicol 
  • Gram-positive infection - Lactamase-resistant penicillins, amoxicillin—clavulanic acid, first-generation cephalosporin, erythromycin, chloramphenicol 
  • Anaerobic bacteria - Penicillin, metronidazole, clindamycin, cefoxitin, chloramphenicol, erythromycin 
  • Bitch with nursing pups 
  • Aerobic bacteria 
  • Gram-negative infection - Cefoxitin, ehloramphanicol 
  • Gram-positive infection - First-generation cephalosporins, erythromycin 
  • Anaerobic bacteria - Cefoxitin, erythromyein, chloramphenicol 
  • You may want to keep the pups nursing the bitch if possible, because this will keep the glands drained. 
  • If there is an open abscess or gangrene, then remove pups and hand feed. Treat the abscessed gland as open wound. 

Nonseptic Mastitis

  • The mammary glands are engorged and sensitive. 
  • There is usually no fever and the bitch is not sick. 
  • Encourage nursing by the pups. 


  • With galactostasis you see hard, caked glands because the bitch is not producing milk. 
  • Give symptomatic relief by soaking the glands, analgesia for the bitch, and encouragement of nursing by the pups. 

Once the dead skin has come away and the hole has formed you can use Epiotic as a spray on. Ironically, this is also an ear cleaner but is excellent for flushing of wounds. The wound will heal and contract within 5 - 10 days

Note: Each mammary gland and nipple should be checked at least once a day for redness, hardness, discharge, or streaking colour. If mastitis develops, the veterinarian should be notified immediately. If caught early, milking out the affected gland and applying hot compresses will help prevent a spread of the problem. Sometimes, antibiotics are necessary. If she gets multiple glands with mastitis, the puppies will need to be bottle fed. The puppies' nails should be trimmed weekly starting within days of birth. This will help prevent some of the scratches on the dam's mammary glands. The deciduous teeth start coming in around day 11. Check the mammary glands of the bitch daily for bite marks.


The frequency of mammary neoplasia in different species varies tremendously. The dog is by far the most frequently affected domestic species, with a prevalence ~3 times that in women; ~50% of all tumors in the bitch are mammary tumors. Mammary tumors are rare in cows, mares, goats, ewes, and sows. There are differences in both biologic behavior and histology of mammary tumors in dogs and cats. About 45% of mammary tumors are malignant in dogs, whereas ~90% are malignant in cats, and dogs have a much higher number of complex and mixed tumors than do cats. 

Etiology: The cause of mammary tumors is unknown in any species except mice, in which an oncornavirus is causative in certain inbred strains. Hormones play an important role in the hyperplasia and neoplasia of mammary tissue, but the exact mechanism is unknown. Recent work in animals has demonstrated estrogen or progesterone receptors (or both) on mammary tumor cells, which may influence the pathogenesis of hormone-induced mammary neoplasia as well as the response to hormone therapy. 

Genetic and nutritional effects on mammary neoplasia have been identified in mice and some people but not in dogs or cats. From a practical view, all mammary tumors should be regarded as potentially malignant regardless of the size or number of glands involved. Spread of mammary carcinomas in both dogs and cats is primarily to regional lymph nodes and lungs. In dogs, 5-10% of mammary carcinomas may produce skeletal metastases, primarily in the axial skeleton, but also in long bones. 

Canine Mammary Tumors: Mammary tumors in dogs are most frequent in intact bitches; they are extremely rare in male dogs. Ovariectomy before the first estrus reduces the risk of mammary neoplasia to 0.5% of the risk in intact bitches; ovariectomy after one estrus reduces the risk to 8% of that in intact bitches. Bitches neutered after maturity have the same risk as intact bitches. The two posterior mammary glands are involved more often than the three anterior glands. Grossly, the tumors appear as single or multiple nodules (1-25 cm) in one or more glands. The cut surface is usually lobulated, grey-tan, and firm, often with fluid-filled cysts. Mixed mammary tumors may contain grossly recognizable bone or cartilage on the cut surface. 

More than 50% of canine mammary tumors are benign mixed tumors; a smaller portion is malignant mixed tumors. In the latter, epithelial or mesenchymal components, either singly or in combination, may produce metastases. Histologically, canine mammary gland tumors have been classified by the World Health Organization as carcinomas (with six types and additional subtypes), sarcomas (with four types), carcinosarcomas (mixed mammary tumors), or benign adenomas. This classification scheme is based on the extent of the tumor, involvement of lymph nodes, and presence of metastatic lesions (TNM system); it includes unclassified tumors and apparently benign dysplasias. 


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