(The following article, reprinted with permission, was taken from the 2008 Canine Breeder’s Symposium, sponsored by the Society for Theriogenology and the American Kennel Club Canine Health Foundation. The Society for Therinogenology will be holding another Breeder Seminar on August 29, 2009 in Albuquerque, New Mexico. It will be a one day seminar and you can find more information and registration requirements posted on their website at http://www.therio.org in the near future.)
Mastitis and Common Mammary Disorders of the Bitch
Anne M. Traas, DVM, Diplomate ACT
Mastitis is inflammation of the mammary gland associated with infection. Mastitis can occur anytime during lactation including lactation at the end of false pregnancy. The most common bacteria isolated are coliforms, staphylococcus sp. and streptococcus sp. These bacteria are normal inhabitants of the intestines and skin of dogs.
Bitches housed in dirty environments or unhygienic conditions, bitches in poor body condition, and bitches that are heavily parasitized or systemically ill are all predisposed. Puppies with long nails can predispose the bitch to infection due to trauma from the nails. In addition, galactostasis (see below) can predispose a bitch to mastitis.
Typically, affected glands are reddened, firm and painful. Mastitis may involve only a portion of a gland, one whole gland or several glands. Milk from the affected glands can be normal in color (yellowish white if colostrum or white in normal lactation), greenish-yellow, brown or red and can have flakes or clots .
Abscessation and/or gangrene of the glands can be present in severe cases and can occur rapidly (this is an emergency). In these cases the glands may also appear dark or black in color. This type of disease can rapidly lead to a systemic infection, also known as sepsis.
If the bacterial infection in the glands is severe enough the bitch may have systemic signs of illness. The signs can include depression, neglect of pups, anorexia, lethargy, fever and/or shock.
Chronic or sub-clinical disease:
Failure of puppies to thrive can be a sign of sub-clinical disease. It is not known how common this condition is in dogs. It is important to note that mastitis does not appear to be the cause of “toxic milk syndrome” (see below) in puppies .
Microscopic examination of milk confirms the presence of pus instead of milk (milk may have a few white blood cells naturally but should not be made up of entirely them) and bacteria can be seen. Culture and sensitivity should be performed. CBC (complete blood count) may show signs of response to infection. Ultrasound may be helpful in diagnosis and in locating areas of abscessation .
Treatment is focused on management of the infection of the gland. The patient is started on broad spectrum antibiotics until culture and sensitivity results are available. The choice of antibiotic is important, as a drug that will enter and hopefully concentrate in the milk is needed. Many factors influence the choice of antibiotic including, lipid solubility, drug pH, integrity of the blood-milk barrier, and a drug’s safety for puppies if they are nursing.
The gland should be hot packed or soaked in warm water, and milked out twice a day if the puppies are avoiding the mastitic glands. Puppies do not need to be weaned unless the bitch is septic, the gland is abscessed, the antibiotic needed is unsafe in neonates or the bitch is neglecting them. Continued nursing, will in fact, prevent engorgement.
The risk of septicemia to the puppies from the mother has not been well studied. One study found the same bacteria in both septicemic puppies and mastitis in the mother, though it is possible that the puppy introduced the bacteria into the teat causing disease in the mother and not the other way around . In addition some antibiotics, although safe for the puppies, may inhibit the normal bacteria in the intestinal tract, causing diarrhea. The weights of puppies should be monitored daily to be certain they are gaining appropriately.
Systemically ill patients should be stabilized first, and then if abscessation or gangrene is present the infected and dead tissue should be surgically removed and drains placed. The entire gland may need to be removed in rapidly progressing cases, especially in the case of gangrenous mastitis.
Cooked white cabbage leaves applied to the glands then wrapped with vet wrap for two hours is anecdotally reported to help draw out fluids and infection. The author has not used this therapy and no studies have been done in dogs and cats however a few promising studies have been done in women . Unpublished anecdotal reports suggest it may help.
Keep whelping areas very clean. The bedding in the box should be replaced 1-2 times a day and the box scrubbed and disinfected once a day. Toenails of puppies should be kept trimmed to avoid trauma to the gland. Glands should be checked by the owner daily as part of the routine post-partum care of the bitch and her puppies.
Also called pseudocyesis or false lactation, false pregnancy is a normal occurrence in the bitch due to the natural fall in progesterone at the end of diestrus. It can also be observed if a bitch is spayed in diestrus or if progesterone drugs are withdrawn. It perhaps should have been called “false lactation” as this is why owners often present the dog.
If clinical signs are noted they typically occur 2 months after the end of estrus. Some bitches will have no clinical signs whereas others will gather stuffed animals, “nest”, and begin to lactate.
The diagnosis is based on clinical signs and a history of the bitch being in heat 2 months ago. A thyroid profile can be helpful as elevated TSH levels may increase prolactin secretion in a bitch with hypothyroidism.
Most bitches will resolve spontaneously in about 2 weeks. Bitches should be prevented from self stimulating the glands through licking, which will prolong the lactation. A child size T-shirt or ace wraps can be applied to keep her from licking. The glands should not be manipulated, hot or cold packed as this often prolongs lactation.
In bitches that do not resolve within 2-3 weeks medical therapy may be necessary. Withholding food and rationing water to ½ of normal intake for 24 hours can help her “dry up”. Cabergoline (dopamine agonist) is an expensive but effective treatment with few side effects. Bromocriptine is a similar drug that is less expensive than cabergoline but can have the unwanted side effects of vomiting and/or diarrhea. These side effects are minimized by starting at a low dose and increasing slowly over a few days and by administering with food. Mibolerone can be used but is an anabolic steroid hormone and also can have side effects, however they are less common and different than with bromocriptine. Progestogens (i.e. progesterone) should not be used as the signs will recur when the drug is withdrawn.
Pain medication can be given to very uncomfortable animals, but sedation with phenothiazine tranquilizers should be avoided as they can increase prolactin secretion leading to increased milk production. Recurrence is common as this is a normal process, but can be prevented with a spay once signs have resolved.
AGALACTIA / HYPOGALACTIA
Agalactia is the inability to produce milk and is rare in the bitch. It is sometimes seen in bitches on progesterone supplementation for suspected progesterone deficiency.
A more common scenario is inadequate milk production, hypogalactia. This may be seen in maiden or nervous bitches, bitches that whelp prematurely, bitches with small litters that are not being stimulated adequately, bitches with inadequate water or food intake, bitches in poor body condition or bitches that are heavily parasitized.
Oxytocin is unlikely to be effective in true agalactia as it only helps with milk letdown and not with milk production or gland development. It may help in cases of nervous or new mothers who are reluctant to nurse a litter especially when used as in combination with phenothiazine tranquilizers (these can stimulate prolactin secretion). Although injectable oxytocin has a very short half like, the combination allows the puppies to nurse and then stimulate normal oxytocin production by nursing. Domperidone (a dopamine antagonist) can be used to promote mammary development with few, if any, side effects (soft stool may develop). Metoclopramide, a drug normally used to enhance gastrointestinal motility and reduce vomiting, also indirectly increases prolactin levels. It may be used if domperidone is unavailable, but has the potential to cause some neurologic side effects (excitation, anxiety) especially when administered at higher dosages because it does cross the blood-brain barrier. If metaclopromide is used, the bitch’s behavior should be carefully monitored. These medications may also be used in combination with oxytocin to stimulate milk letdown, especially in nervous bitches.
This is the build up of milk in the mammary glands due to delayed passage of milk out of the teat ducts. It can be due to the normal weaning process, when there are no puppies to nurse or if puppies are removed abruptly.
Anti-inflamatory pain medications can be used to increase comfort and reduce inflammation. Engorged glands should not be milked out as this will only continue or increase milk production. Therapies that decrease milk production can be used as described above in the treatment for false pregnancy. Wrapping the glands may help to decrease milk production due to hormonal feedback to the brain and also keeps the bitch from self stimulating . If decreased milk production is not desired because the puppies would be put back on the bitch in a short period of time, the glands should be regularly milked out by hand and medications should not be used unless mastitis develops.
TOXIC MILK SYNDROME
This diagnosis is often used when the cause of death of pups can not or is not determined. It is easy to “blame” the milk when puppies die unexpectedly, however, there are many causes of neonatal death and disease. It is important to perform diagnostic tests (necropsy, blood tests, cultures etc.) to determine the actual cause of death. Some of these puppies may in fact be dying of diseases that can be transmitted via the milk however, they may also be suffering from treatable or preventable diseases, such as herpes virus or hypothermia for example. This term is not discussed in modern human medicine and it is the author’s opinion that this diagnosis should no longer be used in veterinary medicine.
Mammary cancer is the most common cancer in female dogs. 50% of canine mammary tumors are benign (most commonly fibroadenoma) and 50% are malignant (most commonly adenocarcinoma). Adenocarcinoma commonly metastasizes to the regional lymph nodes and lungs. The caudal glands are most commonly affected.
One or more lumps in the mammary glands of the intact or spayed bitch is a sign of mammary cancer. Rapid growth of a mass or the presence of a large mass more commonly indicate malignant disease than benign disease. In rare cases a condition called inflammatory mammary adenocarcinoma may present similarly to mastitis with red, painful glands and systemic disease .
Initial diagnosis is made by palpation of one or more masses in the mammary glands. Multiple masses are common. Fine needle aspirate or touch prep cytology of ulcerated masses can often give a preliminary diagnosis. However, a negative cytology does not mean that a tumor is not malignant since many mammary tumors do not readily shed cells making an accurate diagnosis difficult with cytology alone. Tissue should always be sent for histopathology (microscopic analysis) to confirm the diagnosis. Radiographs of the chest and an abdominal ultrasound to check for metastasis should be performed when malignancy is diagnosed.
Surgical removal of the masses along with spay is highly recommended but spaying may not be an option in valuable breeding animals. Even benign tumors can become quite large and uncomfortable, making them difficult to remove. Several surgical procedures have been recommended but there is no evidence that any individual procedure correlates with increased survival time. A more radical surgery, such as an unilateral mastectomy may be associated with decreased recurrence at the site. Unfortunately, studies have demonstrated that the type of surgery has no effect on the cancer free interval [7-8]. Total mastectomy (removal of all glands with or without the lymph nodes is rarely performed as there is not usually enough skin left to close the incision and only one paper has shown improved survival . If a spay is performed at the same time as surgery to remove a tumor, the spay should be done first to prevent seeding the abdomen with neoplastic (cancer) cells. Chemotherapy and radiation therapy are not well characterized in the dog although protocols do exist.
Surgical procedures used are as follows:
- Lumpectomy – removal of mass only, with or without wide margins
- Simple mastectomy – removal of the entire gland containing the mass
- En bloc dissection – removal of the entire gland containing the mass and the regional LN and lymphatics
- Unilateral mastectomy – removal of the entire chain of glands with or without the regional lymph nodes
The prognosis is very good for benign masses. Malignant masses <2cm have a fair to good prognosis after surgical removal. After surgical removal, dogs whose tumors were less than 3 cm in diameter had a significantly increased duration of survival, with a median of 22 months versus 14 months for dogs with tumors greater than 3 cm in diameter .
Dogs spayed before the first estrous cycle have 0.5% the risk of developing cancer when compared to intact dogs, dogs spayed between estrus 1 and 2 have 8% the risk, those spayed after 2 cycles have 26% risk. After the second cycle it is unclear what the exact benefit of spaying is on risk of mammary cancer, but it is believed that there is some reduction in incidence even with aged bitches. Pregnancy has no effect on the risk of developing mammary cancer. . Exogenous progesterone administration (typically used for keeping a dog out of heat) can increase the risk. [11-12]
Mammary cysts, also called fibrocystic disease of the mammary gland or blue dome cysts, may have a hormonal basis. Is occasionally possible to aspirate clear to brown fluid from the mass. The major concern with this condition is making sure that the masses felt are cysts and not lumps. The best way to do this is by removing them or taking a tissue sample from them. Fine needle aspirate may also help but is not as good as biopsy. The ability of these cysts to develop into cancer is not known 
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 Allen SW, Mahaffey EA. Canine mammary neoplasia: Prognostic indicators and response to surgical therapy. J Am Anim Hosp Assoc 1989;25:540-546.
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 Philibert JC, Snyder PW, Glickman N, Glickman LT, Knapp DW, Waters DJ. Influence of host factors on survival in dogs with malignant mammary gland tumors. J Vet Intern Med. 2003 Jan-Feb;17(1):102-6.
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Last Updated: 02/16/2009, 10:27 am