The secret to managing mastitis, a bacterial infection that invades the mammary glands of nursing bitches, is to identify it as early as possible.

“I think most important is to always check the mammary glands,” says Margret L. Casal, D.V.M., associate professor of reproduction and pediatrics at the University of Pennsylvania School of Veterinary Medicine in Philadelphia. It’s easy for breeders, she says, to focus on the rear end of the dog because that’s where the puppies come out, but a twice-daily check of the area around the teats can stop mastitis in its tracks. This is especially important when the puppies start teething, she says. A slight cut in the skin from a wayward puppy tooth can easily allow bacteria into the mother’s skin.

Mastitis can happen at any point during lacation, but when puppies start teething, the risk increases. Photo © Can Stock Photo.

The mammary gland is a complex gland found under the skin in the area of a dog’s teat. The complex gland is made up of many simple glands that secrete milk into ducts that move toward a central duct, then to the teat, or nipple.

“The mammary gland is like a tree,” writes Helena Wensman, D.V.M., Ph.D., of the Swedish University of Agricultural Sciences in Uppsala, in her doctoral thesis on canine mammary carcinomas and sarcomas. “At the tips of the branches, there are glands ready to proliferate, differentiate and produce milk in the case of pregnancy. From the glands run ducts that collate with other ducts with a final purpose to collect and bring the milk to the nipple.”

The nipple, or teat, has about 20 “very small” openings, Casal says.

Just one or a few of the simple glands and associated ducts can be affected by mastitis. Because of this, it doesn’t usually look like the whole area around the teat is affected, Casal says. It can be just one side or even a quarter of the area.

In addition to careful monitoring of the bitch, Casal advises breeders to “keep everything as clean as possible. Wash the bedding very frequently. I know people who wash it three or four times a day.

“Hygiene is very important,” she says.

Most bitches keep themselves clean, but if she needs help, it’s best to use only warm water, Casal suggests. If the situation warrants soap, use a small amount of a mild one.

Another good practice is to monitor the puppies to ensure they are nursing from all the teats, particularly the ones toward the bitch’s hind end. Those last two typically produce the most milk.

Any reddening, increased heat or swelling can indicate that bacteria, usually E. coli (Escherichia coli) or staph (Staphylococci),have entered one or more of the simple mammary glands. Casal points out that the mammary glands also have naturally occurring, non-harmful bacteria. Most of the mastitis cases Casal has seen involve just one complex mammary gland, sometimes two. So, reddening in the area of even just one teat is cause for concern.

There’s no time to waste, according to Casal. Hot compresses, alternated with cold for the bitch’s comfort, can help relieve the swelling and pain, but a bitch with any sign of mastitis needs to see its veterinarian. Not only is mastitis a painful condition, but without antibiotic intervention, the tissue around the teat will burst so that the infection can drain out. It’s a horrible thing, Casal says, with the burst area sometimes as big as a fist. “Without exception, once it goes too far, it will open up,” she says.

Mastitis, which occurs in all breeds and sizes of dogs, has numerous contributing factors, including incomplete drainage of milk from the mammary glands, malnutrition, unsanitary conditions, skin diseases, failure of milk to “drop,” and trauma from puppies being too rough in their suckling. More rarely, it has systemic causes such as metritis, a postpartum uterine infection, or pyometra, a hormonal disorder. Bitches with false pregnancies that lactate can also get mastitis.

While some breeders will manipulate the affected mammary glands to encourage drainage, Casal does not recommend it. “You can do that, but it’s very, very painful,” she says. Hot compresses will help drain the milk, but, if you catch the condition early, “it’s better just to put them prophylactically on the antibiotics, rather than waiting for it to happen.”

In prescribing antibiotics, veterinarians are careful not to give something that has the potential to harm the puppies. Cephalexin and amoxicillin are both appropriate for dogs that are still nursing, Casal says, while tetracycline and aminoglycosides should be avoided because they can lead to long-term health problems in puppies.

The milk from a gland that’s been infected may appear normal or “abnormal in color or consistency,” according to Merck Veterinary Manual.

If the early signs of mastitis go unnoticed, purple spots will appear around the teat. “If you see purple spots, that’s a real emergency,” Casal says. “The skin will look a little bit indented because tissue has died underneath.”

By this point, the bitch will have a fever, and may stop eating and discourage her puppies from nursing. Treatment may include fluids, and the mammary gland will be cut open and drained if it hasn’t yet ruptured.

If there’s an upside to mastitis, it’s that it doesn’t predispose a bitch to repeat infection. Casal says she did once see a bitch that had it twice, but all the other cases she’s handled were one-time events. “It’s not like a pyometra,” she says. “Once you’ve drained out all the milk and everything’s healed up, there should be no more bacteria.”