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Mastitis in Dogs — Causes, Symptoms & Treatments

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Published on
Saturday 6 October 2018
Last updated on
Tuesday 9 May 2023
Mastitis in Dogs
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Canine mastitis occurs when one or several mammary glands are bacterially infected. If detected early enough, the condition can be treated using a course of antibiotics as an outpatient. Otherwise, there might be a need for hospitalization with IV therapy or surgery.

Mastitis is common in pregnant female dogs, especially those with more puppies than teats. This is because the puppies will put their mother’s mammary glands to the test over several weeks. A lack of hygiene along with scratches and cracks may quickly escalate into a bacterial infection.

In order to offer a quick treatment and fast recovery, dog breeders must check their female’s teats every day. Calling the vet early may save a lot of pain and hassle for the dog and yourself.

What is Mastitis in Dogs?

Canine mastitis is a condition in which one or more of the lactating mammary glands becomes inflamed or swollen due to an infection by a bacterium. Mastitis in dogs is associated with breastfeeding and postpartum bitches. It is generally not a concern for lactation resulting from a pseudopregnancy. The bacteria that are most often associated with the inflammation that causes Mastitis are Escherichia coli (E. coli), Streptococci and Staphylococcus.

There are two types of canine mastitis:

  • Galactostasis is the type that tends to show up in the later stages of pregnancy and is marked by caked breasts
  • Acute septic mastitis is when the bacteria have made its way into the mammary gland and caused an abscess

Infection of the mammary glands caused by Mastitis can result in a malignant or benign condition which can be verified by a thorough examination of the mother’s milk. It is a potentially life-threatening condition so it should always be handled with care.

Canine Mastitis is not cancer. Therefore, it should not be confused with canine mast cell tumor, or Mastocytoma, which is a cancerous tumor located on the skin.

What Causes Mastitis in Dogs?

During the whelping phase, a bitch is exposed to various stressors in her life. The stress of pregnancy followed by the nursing, coupled with the sharp teeth of her young creates an infectious ground base for bacteria to prosper. In normal circumstances, the dam’s immune system is able to fight off the bacteria, however, with the lack of proper nutrition or sanitary environments, her immunity is less likely to function at its optimal level.

[pullquote-right]As a consequence of the pain, a female dog victim of canine mastitis will often reject her puppies and avoid nursing all together.[/pullquote-right]

Ascending infection via a teat

One of the most common causes of Mastitis in dogs is the spread of infection via one of the teats. Trauma or injury in one of the nipples or the teat canal allows bacteria to enter the canal. As it travels up the mammary gland, bacteria populate causing an infection. Aside from trauma, certain living conditions can cause the bacteria to ascend due to the various irritants present in the dog’s living space.

Wounds and scratches on the nipples

During pregnancy, a bitch will produce milk in the milk ducts of her mammary glands for supplying nourishment for her pups. However, oftentimes, puppies can become overexcited and overly aggressive while nursing. They often scratch the mother’s nipples during feeding. Furthermore, nipples can often become cracked due to aggravation. These cracks and scratches provide a playground for bacteria to gain momentum and cause an infection beginning in the milk ducts.

Poor hygiene

Aside from injury, a bacterial infection of the breasts in dogs is often caused by poor hygienic standards of living. Lack of hygiene in a dam’s living quarters can wreak havoc on her health as these places are replete with bacteria and other adverse properties. That said, not only is the living space a feeding ground for germs, but also the space around the mum’s nipples. Therefore, proper hygienic practices such as regular cleaning of the dog, her breasts, and around her nesting space are required for prevention.

Other Causes

Other common causes of Mastitis include systematic infections that originate elsewhere in the body and make their way to the teat. Milk accumulation in the mammary duct due to prolonged periods of the milk production may increase the chances of bacteria buildup and lead to inflammation. In more serious cases, Mastitis can be a symptom of mammary gland cancer. Because of this, it’s vitally important to get the dam checked as soon as possible as it is not always possible to know what stage of Mastitis she is in or whether the infection is caused by more malignant factors.


Dog owners often notice a change in behavior and appearance in a dam infected by canine mastitis. This change is quite evident in the way she cooperates with her offspring and will most likely alarm her breeder, as long as you are paying attention and monitor the situation regularly.

symptoms of mastitis in dogs
Monitor your female dog to notice a change in behavior and appearance caused by canine mastitis.

Rejecting puppies and less frequent nursing

Due to pain in the infected area of the mammary gland, a dam will begin to reject her puppies and avoid nursing altogether. This is to counteract the extreme discomfort caused by the constant suckling of the pups that further irritates the painful sensation.

As her condition worsens, it may seem she has lost complete interest in her pups and reject any notion to continue the whelping phase. The whelps will cry a lot. While some caretakers may not consider it to be a great deal, this lack of attention is often a sign that indicates something is wrong and she should be checked out.

Visibly swollen and purulent mammary glands

The most prominent signs of a bacterial infection of the breast in dogs are the visible changes noticeable on the teats of the dam. The infected mammary gland will tend to swell up and become distinctly inflamed, swollen, and will begin to show colors of a purulent teat. The infected site will turn red or purple depending on the stage of the advancement and will become more painful.

Often times, after the infection has progressed, the gland may show ulcerative signs and become purulent in which it produces pus-like liquids or blood and show open, visible wounds. Any milk that is expressed from the infected site will produce a more cloudy milk or thicker in composition. Blood and pus may also be found in the extracted milk as well.

Lethargy and overall low energy

A dam that has been infected with the Mastitis infection will show signs of extreme lethargy and fatigue. She will exhibit an overall low energy. She may suffer a loss of appetite, especially when the infection has progressed into inflicting a lot of pain for the mum. These are obvious signs to look for in your bitch that indicate something is definitely wrong and she needs to get checked out. Another sign includes excessive sleep. This is very important to watch out for because these types of infections can spread rather quickly in the body and affect the dam’s overall energy and function.

Other Symptoms

Aside from the most common signs mentioned above, other symptoms to watch out for include lumpy teats that are painful to touch. They may also be very warm or hot when touched. In addition to not wanting to nurse, an infection of the mammary glands may cause the bitch to snap and growl at her puppies. She will exhibit signs of restlessness in the earlier stages before becoming too weak. Some dogs may cry and whimper.


A diagnosis of a complete physical examination of the dam may be all that is required, however, some cases require laboratory results to rule out other diseases and to confirm what was found in the exam. Upon examining your pet, ensure the vet knows the entire history of your dog as well as any events that lead up to the incident to consider possible causes. Dams will undergo a complete blood count analysis along with a chemical blood profile and a urinalysis.

The complete blood cell count will determine the number of white and red blood cells present along with the platelets. Another lab test commonly used is the milk cytology test in which droplets of her milk are thoroughly examined under a microscope to detect white blood cell counts or bacteria. In the event that Mastitis is not responding to antibiotic treatment, a bacterial culture test may be required in which milk is extracted from the infected site and the bacterium is isolated for testing.


Canine mastitis in dogs may be treated with a course of antibiotics, an intravenous fluid therapy, or surgery. The treatment will depend on how early the mastis was detected and diagnosed.


An antibiotic treatment is generally the quickest way to treat and recover from mastitis. They promote an easier recovery while not needing any hospitalization. Treated bitches are able to stay in the comfort of their own home.

In fact, most cases of mastitis in dogs end up with outpatient treatments unless the infection is progressed. That’s why it’s important to get the dog treated right away. During this at-home treatment phase, dogs will normally be prescribed pain medications with oral antibiotics. Antibiotics may pose a threat to nursing puppies, however, as it is possible they can be passed through the mother’s milk.

Intravenous fluid therapy

If the dog’s mastitis infection is severe, the dog needs to be hospitalized. During this process, the bitch will be treated with intravenous fluid therapy as well as injectable medications to keep her stable. Fluid therapy is also needed for dogs who are having difficulties with weight management, for example. This fluid therapy will help keep her at an even weight and provide the necessary nutrients she needs for healing during the treatment.

In some worst cases, the surgical removal of the infected glands may be required.

Milking out the affected mammary glands to keep tracts clean

For less serious infections, breeders and dog owners may manually milk the duct by hand. The hand-milking movement will alleviate pressure from the infected teat and helps to increase the blood flow. This will greatly improve the dam’s condition and encourage healing. The milking should be done every six hours for optimum results.

Although dog breeders have the option of manually assisting in the treatment of mastitis, this should be recommended by your veterinarian rather than your own opinion. This is then done on an outpatient basis, meaning the bitch does not require hospitalized.

Can puppies nurse from a female with mastitis?

In most cases, it is best not to allow puppies to continue nursing after the bitch is diagnosed with canine mastitis in one of her mammary glands. In the early stages, puppies may be more adequately fit to extract milk from the glands as opposed to hand-milking but there will always be the concern of whether the antibiotics used in the treatment may pass over to the puppies. Additionally, the bitch may, in fact, be too sore to allow nursing to continue.


Having said that, dog breeders will be forced to take nursing matters into their own hands by bottle-feeding the litter. In these cases, buy some high-quality puppy formula replacement and get the puppies on a regular feeding schedule just as they would while they were nursing. Buy a bottle and feed them accordingly. This should be done until the mammary glands are all sound and clear from any infection.

Prevention and Avoiding Recurrence

Canine mastitis can be a dangerous condition if not treated correctly or on time. Dogs who have had mastitis in the past are more likely to develop it in the future so prevention is key. A female who went through canine mastitis should generally be removed from your breeding program.

Fortunately, there are certain steps one can take to minimize the occurrence or to help prevent it in the first place. It’s important to increase your hygiene standards in caring for the bitch and keep her surroundings always clean, especially in the places your dog tends to frequent most such as her nesting place. Another tip is to shave the mammary glands as well as shaving around each teat. In order to prevent mastitis and other infections, it’s vitally important to clean the breasts of the dam with wet gauze or salt water on a regular basis. Also check her nipples regularly.

Many causes of mastitis in dogs can be traced back to the everyday play between puppies and their mothers. Through injury to the mother’s nipples, bacteria can easily find its way in the mammary glands. These injuries are commonly caused by the scratching and cracking of the pup’s nails and teeth. Therefore, keep their nails trimmed regularly.

During nursing, give your bitch a weekly salt bath and make sure all of her teats are used by the pups. In the event of the number of teats exceeds the number of pups, organize a rotation between feedings so that all teats get used. In any case, in order to avoid worsening of symptoms once the mastitis is diagnosed, early intervention is imperative to keep the bacterial infection from culminating into a life-threatening ordeal.

One comment on “Mastitis in Dogs — Causes, Symptoms & Treatments”

  1. Mable

    How long does it take for pups to wean?

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