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.

Diagnosis In-depth

Many times the diagnosis of mastitis is based on the history, physical exam findings and response to therapy. In a young, lactating mother with a warm, painful, swollen mammary gland, and a low-grade fever, a tentative diagnosis of mastitis is often assumed. Additional tests to confirm the diagnosis is usually a reasonable approach, but might not always be practical. Placing the animal on antibiotics and an ensuing resolution of clinical signs supports the presumed diagnosis. Some recommended tests may include:

• Fluid analysis. Analysis of the milk or discharge is the most reliable diagnostic test. The milk that is evaluated microscopically will have an elevated white blood cell count (above 3000 cells/mcl). The predominant cell type of the fluid should be degenerate neutrophils (white blood cells that fight bacterial infections). Many times free bacteria or bacteria within the white blood cells will be noticed. Evaluating the fluids pH measurement (a measure of the acidity of the fluid) may also provide useful information to aid in appropriate antibiotic selection, as different antibiotics work better at different pH measurements.
• Aspirate and cytology. Occasionally, an animal with mastitis will not have any expressible milk for evaluation. A hard firm, painful swelling or a softer, more fluid filled swelling may be present. These swellings may be aspirated and the retrieved fluid evaluated microscopically. Usually, only a very small amount of fluid (perhaps only in the hub of the needle) is recovered, although if an abscess is present, a large amount of fluid might be present. The cytologic findings should be similar to those seen in mastitic milk.
• Culture and sensitivity. Culture of the milk or discharge is another useful test in determining appropriate antibiotic therapy. When the fluid is cultured, the bacteria that are causing the infection will grow and the effectiveness of various antibiotics may be tested. The most common bacteria cultured are E. coli, staphylococcus or streptococcus.
• Complete blood count (CBC). This is a useful test since many animals with mastitis have an increased white blood cell count. If the white blood cell count has a left shift (the neutrophils are more immature) or contain degenerative bacteria it would be compatible with the more serious septic condition. Some septic animals may also have low white blood cell counts.
• Biochemical profile. In a more ill animal a biochemical profile is indicated to evaluate other body systems. If sepsis is present, a low blood sugar may be found. Liver and kidney function are also evaluated. Underlying metabolic conditions that may predispose an animal to have more serious disease, or potential sequelae from sepsis may be identified.
• Urinalysis. If kidney function is a concern, a urinalysis should always be submitted. A urinary tract infection should also be ruled out as a potential problem. The urine is cultured if needed.
• Chest and abdominal radiographs. X-rays are potentially useful in the septic animal. Underlying or additional sources of infection may be identified. Pneumonia, abscesses or cancerous processes may be found.
• Blood cultures. If an animal is very ill and suspected of being septic, blood cultures should be taken upon admission. To maximize accurate results, antibiotics should not be started until the cultures are taken. Generally two cultures are taken one to two hours apart. Appropriate long-term antibiotic therapy may be based on these results.

Therapy In-depth

The treatment for mastitis is usually fairly uncomplicated and rapidly responsive to antibiotic therapy. Treatment of the nursing neonates is usually more labor intensive and difficult. There is some debate on whether or not to let the nursing animals continue to do so. The continued nursing of the neonates, if allowed by the dam, is actually beneficial in the treatment of mastitis since the infected milk is continually drained from the teat. Additionally, the ingestion of infected or antibiotic containing milk is generally not a problem (unless the gland is abscesses or gangrenous) in the young animal. However, the infected milk is of poorer nutritional value, so neonates usually will require nutritional supplementation. Indications for weaning puppies include milk that is grossly purulent, discolored, foul smelling or puppies not nursing on their own, losing weight or puppies with associated vomiting and/or diarrhea.

Occasionally, mastitis may be associated with septicemia or a bacterial blood infection. This requires much more aggressive care and hospitalization. It is a life threatening condition, but fortunately is only rarely seen.

Some treatments may include:

• Systemic antibiotic therapy is the most important part of the treatment. If available, antibiotics should be given on the basis of the bacterial culture and sensitivity results. The pH of the milk can also help in determining the best drug. Usually antibiotics are given orally at home, but if the animal is very ill, antibiotics may need to be administered intravenously in the hospital. Antibiotics are usually administered for 10 to 21 days.
• Warm water compresses are useful in promoting the drainage of the infected fluid out of the body. It also may promote blood flow and antibiotic penetration into the diseased tissues.
• Affected glands should be expressed as needed to keep the gland empty of abnormal fluid. Continued nursing of the puppies or manually milking may achieve this. Manual milking may be difficult, but warm water compresses often help.
• Occasionally, a large accumulation of infected material (an abscess) will accumulate within the mammary tissue. This material will need to be surgically drained so that the antibiotic therapy will be more affective. A small incision is made on the swelling releasing the abnormal fluid. Once opened, there is usually a small amount of continued drainage from the surgery site. Continued drainage should be encouraged.
• Gangrenous, necrotic (consisting of dead tissue) or persistently infected glands often will require surgical excision. A mastectomy (removal of the mammary gland) is rarely needed but may be required if other therapies are failing.
• Septic animals require intravenous fluid support. Fluid therapy may be needed for several days or more depending on clinical condition of the patient. Septic animals are often critical and may require intensive care at a specialized or emergency center.
• Drugs may also be used to stop lactation. Antiprolactin therapy may be administered.
• It is important to ensure that the puppies are weighed daily to ensure they are receiving adequate nutritional intake. For more information on caring for puppies, please read Orphaned Puppy Care.

Follow-up Care of Dogs with Mastitis

Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not improve rapidly.

Administer all medications as directed. Alert your veterinarian if you are experiencing problems treating your pet. Make sure she is eating and drinking adequately.

Apply warm water compresses as directed by your veterinarian. Usually, no more then a few days of compresses are needed at home. Make sure the affected glands are decreasing in size and becoming less painful with time. With treatment, the glands should normalize. Make sure the infection or swelling is not spreading to the other glands.

If neonates are weaned, they will need to be hand-reared. A variety of milk replacement products are available.