Mastitis in Dogs
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.
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.