Nursing mothers may avoid feeding whelps due to the pain caused by mastitis, which can lead to whelp malnourishment. Mastitis is most commonly caused by infection, and in severe cases, can lead to significant health issues and even death in the mother and nursing babies if not treated. The condition is one of the most serious illnesses diagnosed in dairy cattle,1 but is also seen in dogs and, less commonly, cats. According to the American Kennel Club (AKC), mastitis is typically caused by a bacterial infection, but may also be caused by fungal infections. Common pathogens known to cause mastitis include Escherichia coli, Staphylococcus sp., and Streptococcus sp.2 “In cats, mastitis may also occur secondary to mammary hyperplasia, a proliferation of tissue within the mammary glands that occurs as a result of elevated progesterone levels during diestrus, the period after estrus/mating,” says Gene Pavlovsky, DVM, medical director, Veterinary Medicine South Clinic, University of Illinois College of Veterinary Medicine in Urbana. “Galactostasis, a backup of milk that can occur when puppies or kittens are not nursing, may also be a cause,” adds Dr. Pavlovsky. Though uncommon, mastitis can also occur in non-nursing dogs as an indication of a type of cancer known as inflammatory mammary carcinoma, says Elizabeth Rozanski, DVM, DACVECC, DACVIM, associate professor in the emergency and critical care section at the Tufts University Cummings School of Veterinary Medicine in North Grafton, Massachusetts. “If a dog is nursing, mastitis likely is caused by a bacterial infection,” Dr. Rozanski says. “But if we have a situation in which the dog has what looks like an open sore on a mammary gland and hasn’t recently had puppies, we get more worried because it could be cancer.” The prevalence of mastitis in dogs is difficult to determine. A 2021 retrospective cohort study published in the journal Animal Reproduction Science used data from two guide dog colonies collected over 17 and 10 years, respectively. Of the 3,076 whelping that occurred during the respective study periods, clinical mastitis was diagnosed in 13.2 percent (408 cases), with the average day of diagnosis being 16.7 postpartum.3 Presentation Indicators of mastitis include swollen, inflamed, discolored mammary glands that may also be scabbed over and sensitive to touch. The affected glands may also be different in texture and hot to the touch. “Not all glands may be affected; sometimes it’s just one gland and sometimes it’s all of them,” says Pavlovsky. “Owners should be aware of specific signs, such as the mother preventing her babies from nursing because it is painful. If that happens, the babies may fail to thrive and gain weight because they do not have good access to milk. In some cases, this can be a completely asymptomatic problem, at least initially, especially when it has not yet resulted in visible swelling or inflammation.” In extreme cases, the affected mammary glands may become necrotic, requiring surgery. The affected gland may have a dark or bloody discharge and appear bruised or discolored. “In cases where you have necrosis of the glands, the necrotic tissue can be removed, drained or flushed, though in severe cases removal of the gland may be required, especially if there is a lot of tissue damage,” Pavlovsky says. Diagnosis A visual examination of the affected glands, supported by symptoms exhibited by the patient, is the most common way that mastitis is diagnosed, Pavlovsky says. “A bacterial cause of the infection can be confirmed through cytology, or an evaluation of cells present in the milk,” he adds. “That could reveal a presence or increase in certain types of inflammatory cells that are not present in normal milk.” An ultrasound of the affected glands can also help diagnose mastitis, Pavlovsky says. “In a healthy mammary gland, you can easily distinguish the normal architecture,” he explains. “When the glands are really inflamed, you sort of lose that distinct architecture and everything appears washed out on the ultrasound, which can help find areas where there may be fluid that shouldn’t be there. This all comes together as part of a bigger puzzle. Put that together with the history, physical examination, and other signs, and that gives you a more definitive diagnosis.” Treatment Antibiotics are the first line of treatment for mastitis, especially for relatively mild to moderate cases in which the patient is systemically well and does not require hospitalization. However, in cases in which the condition has gone undetected for some time, the bacterial infection may spread beyond the mammary glands to other organs, resulting in sepsis. This is commonly confirmed through bloodwork that reveals an elevated white blood cell count, and often results in hospitalization. “A culture sample of the milk may be obtained to guide antibiotic therapy because the culture will confirm what bacteria are involved and which antibiotics would be most effective,” Pavlovsky says. Ancillary treatments include warm compresses to encourage drainage, and hand-milking the affected gland to reduce milk backup until the inflammation has subsided. Effects Mastitis can have a dramatic effect on the quality of life of both the animal and its owners. “Mastitis can be very painful,” Rozanski says. “It can become a systemic infection, though most of the time it remains local. Like a wound that gets infected anywhere, the patient is uncomfortable and can sometimes run a fever and not feel like eating.” This can create difficulties for the pet owner, who must hand-feed the puppies or kittens while the mother heals. Pavlovsky recalls a patient that developed mastitis in the majority of its mammary glands after birthing 12 puppies. “We were involved quite heavily in client education on how to feed all of those puppies because the mother was unable to sustain them,” he says. “It was quite a job for the family to hand-feed them. I believe they involved their children and neighbors and anyone else they could find because it was a monumental effort to feed the hungry little things every few hours.” There may be financial or other hardships for pet owners as well. Rozanski was involved in the treatment of a pit bull that developed mastitis in several mammary glands after delivering a litter. “The case was pretty serious, requiring frequent return visits for wound management,” she notes. “The family had limited resources, and ended up having to walk several miles to get to our clinic every time their dog required care. The dog ultimately did all right, but it was one of the worst mastitis cases I have seen.” Client education can go a long way toward preventing mastitis in dogs and cats. For example, it is very important that the whelping box or area is kept clean and dry. Puppies should also have their nails trimmed as needed to make sure they don’t accidentally nick a mammary gland while feeding, leading to infection. “It’s also important that puppies nurse from all of the mother’s mammary glands to avoid a backup of milk,” Pavlovsky says. In addition, owners should regularly examine a nursing mother’s mammary glands for signs of inflammation, such as pain, swelling and redness. “That kind of early detection is important,” Rozanski says. Don Vaughan is an award-winning writer who frequently writes about veterinary-related topics. References https://www.zoetisus.com/conditions/dairy/mastitis.aspx Mastitis in Nursing Mother Dogs by Paisley Lunchick, RVT KPA-CTP https://www.akc.org/expert-advice/dog-breeding/mastitis-in-nursing-mother-dogs/ Incidence and risk factors for canine mastitis and metritis in two guide dog populations by Jennine Lection, Alyssa J. Cornelius, et al. Anim Reprod Sci. 2021 Augs:231:106802. Doi: 10.1016/j.anireprosci.2021.106802. Epub 2021 Jul 7. https://www.sciencedirect.com/science/article/abs/pii/S0378432021001172 https://www.petmd.com/dog/conditions/endocrine/c_dg_mastitis https://www.purepetfood.com/help/mastitis-in-dogs
