Mastitis in dogs – symptoms, nursing and treatment

Overview

Inflammation may be local or a severe systemic illness

Dogs usually have 5 pairs of mammary glands on either side of the chest and abdomen. Their function is to produce milk for offspring. Mastitis may affect a single gland or several at once.

Milk-producing glandular tissue consists of small alveoli and connecting ducts. Contraction of surrounding muscle-like cells pushes milk into ducts and towards the teat opening. Gland number and position can vary between individuals.

Inflammation is most often bacterial. Prolonged milk accumulation or trauma can nevertheless cause inflammation without demonstrated infection. Alongside acute and gangrenous forms, chronic and subclinical inflammation occur. In the subclinical form, the mother and gland can look normal while puppy growth is impaired.

Causes

How infection develops

The most common route is upwards through the teat opening into the mammary gland. Teat or teat canal damage makes it easier for bacteria to enter tissue. Suckling puppies can cause the skin injury. A dirty environment can also expose the mother to large bacterial numbers without a visible wound.

Associated bacteria include E. coli, staphylococci and streptococci. They also occur in the mother's normal skin microbiota. Less often, bacteria reach a gland through the bloodstream from elsewhere in the body. Postpartum uterine infection can be such a source.

Rarer fungal mammary infections have been described in certain endemic areas and dogs with impaired immune defences.

Milk accumulation

Galactostasis means milk accumulating in a mammary gland with impaired removal. Sudden weaning or a puppy's death reduces suckling and may leave excess milk in the glands. Persistent accumulation can progress to inflammation. In phantom pregnancy, hormonal changes can start milk production without a litter.

Prolactin helps initiate milk production alongside other hormones and regulatory factors.

Risk factors

Mastitis occurs in females of different ages and breeds. Risk particularly involves nursing after birth and high milk production. Milk secretion and accumulation during phantom pregnancy also predispose to problems. Phantom pregnancy signs often appear 6–8 weeks after oestrus.

Poor hygiene, teat injuries and infection elsewhere in the body are predisposing factors. A sudden end to nursing increases accumulation risk. A mammary tumour can be involved in a persistent or unusual inflammatory lesion. Gland signs are therefore not assessed solely according to whether a female currently has puppies.

Typical symptoms

Early on, slower-than-expected puppy weight gain may be the first observation while the mother still appears healthy. Other possible signs include:

• A gland swells or feels firmer than usual.
• The gland feels hot and touching it hurts.
• Skin reddens or turns purple.
• Milk is cloudy, thick, bloody or contains pus.
• The mother eats poorly, has fever or withdraws from puppy care.
• Ulcers or crusts develop on the gland's skin.

Milk can also look normal despite inflammation. A gland becoming dark, cold and foul-smelling may indicate gangrene. Marked vomiting and weakness can accompany spread into systemic illness.

In the chronic form, a gland may be only slightly swollen and feel irregular on palpation.

Complications and consequences

Abscesses, gangrene and illness in puppies

Untreated acute inflammation can spread between glands. It can also lead to tissue rupture. An abscess, or pus collection, may develop within a gland. Reduced blood supply and severe infection can cause glandular tissue death, or necrosis. Severe infection can progress to sepsis, endangering the mother's life.

Bacteria and their toxins in milk can also make puppies ill. This is called toxic milk syndrome. An ill mother may additionally care less well for her puppies. Mastitis can therefore threaten both the mother and litter.

Most appropriately treated cases have a good prognosis. Signs typically settle within 2–3 weeks with treatment. Gangrenous mastitis and sepsis have a guarded prognosis despite intensive treatment.

Diagnosis at the vet

Assessing the whole mother and litter

The history establishes the birth date, puppy numbers, sign duration and possible phantom pregnancy. Your vet examines every mammary gland, rather than only the visibly changed one. Glands are compared for size, symmetry, warmth, consistency and skin colour. Milk colour, consistency and smell are assessed separately.

A blood count helps assess the inflammatory response and its severity. Blood biochemistry can also investigate dehydration and systemic effects. Blood CRP is a marker of inflammation. It does not, however, identify whether inflammation comes specifically from a mammary gland or another disease.

Milk sampling helps distinguish changes

Milk cytology checks inflammatory cells and their changes. Bacteria inside degenerate neutrophils support bacterial inflammation. Occasional immune cells can also occur in milk from a healthy gland. A bacterium visible in a sample alone may instead reflect contamination from the skin.

Milk from an inflamed gland is sampled for bacterial culture and antibiotic susceptibility testing even if it looks normal. The teat and surrounding skin are cleaned carefully for sampling. Culture helps target treatment of bacterial infection.

Marked gland engorgement can be mistaken for a lack of milk even in a mother producing plenty.

A study of 89 females examined 157 mammary gland samples in total. Of 127 postpartum samples, 28, or 22%, were classified as subclinical inflammation. Acute inflammation was found in 17 samples, or 13%. These are gland-level findings from a selected group, rather than disease risks for all nursing females.

In the same postpartum sample group, 66 of 127 glands, or 52%, were clinically healthy. Interpretation therefore considers each gland's own findings.

Imaging and excluding a tumour

Ultrasound can help assess internal gland abnormalities. Inflammatory mammary carcinoma, a cancer, must be distinguished from ordinary mastitis. Abnormal tissue may need biopsy to exclude a tumour.

Structural changes in subclinical inflammation are not always visible on imaging. If a mammary tumour is suspected, chest X-rays can check for possible spread to the lungs.

Treatment

Treatment depends on severity and the puppies' situation

Mastitis needs a veterinary examination and a treatment plan suitable for both the mother and puppies. A milder infection in an otherwise well mother can often be treated at home after a consultation. An antibiotic is selected for bacterial infection. The choice considers whether it may pass into the milk and affect the puppies. The safety of pain relief for nursing puppies is also assessed.

Your vet may advise gently emptying the gland to prevent secretions building up. Local care may involve warm or cool compresses, depending on the situation. Keeping the gland area clean is part of treatment. Whether and how milk is expressed depends on the mother's pain and the puppies' nursing; practical instructions are needed for home care.

Can the puppies continue nursing?

In some situations, puppies can nurse from healthy glands. With mild local inflammation, access to the affected gland can be blocked separately. If the mother is systemically ill, the puppies may need to stop nursing and receive milk replacer. Medication unsafe for puppies, several abscessed glands or the mother's unwillingness to nurse may also require supplementary feeding or weaning. The decision is based on examination findings in the mother and puppies; milk appearance alone does not establish whether nursing is safe.

Severe infection and reducing milk production

A severely ill mother may need hospital care, intravenous fluids and injectable medicines. An abscess may need opening and draining. Dead or severely inflamed tissue may require surgical removal. For engorgement associated with phantom pregnancy or an already weaned litter, a medicine blocking prolactin's effects may be considered to reduce milk production.

Monitoring the response

During follow-up, falling CRP can support the impression that tissue damage is settling. It is assessed alongside the mother's clinical recovery.

Prevention

Keep the whelping box and the mother's bedding clean so the teats are not constantly in contact with a dirty environment. Change bedding at least 1–2 times a day and clean the box daily. Remove sharp edges from the mother and puppies' living area to reduce teat injuries. Keep puppies' claws short so they do not break the skin over the mother's glands.

Monitor nursing so milk does not remain in only some glands for a long time. Avoid abrupt weaning, as this can cause milk to accumulate in the glands. By contrast, expressing or massaging teats during phantom pregnancy alone increases milk production. Advice for managing an otherwise symptom-free phantom pregnancy and emptying treatment for confirmed mastitis therefore cannot be used interchangeably.

Important for dog owners

Monitor the mother and every puppy

Check puppies' weights daily to identify poor weight gain early. Record each puppy's weight separately and note changes in nursing or behaviour. Check gland appearance and the mother's willingness to nurse at the same time. Do not limit your observations to the teat that first looked painful. All mammary glands are assessed during the clinical examination too.

The consultation needs details of the most recent birth, litter size and how long signs have lasted. The puppies' age and whether they still nurse affect medicine choices. Bring the mother's medication list. Ask for a written plan stating which glands puppies may nurse from, how to provide supplementary feeds and which changes mean you should contact the vet again. Also establish how any milk expression and local care should be carried out without causing the mother unnecessary pain. Treatment may include milk replacer if the puppies cannot get enough milk from their mother.

Frequently asked questions

Can mastitis occur without puppies?

Yes. Mastitis can also occur in a non-pregnant female whose glands produce milk. Phantom pregnancy can involve gland enlargement and milk production. However, examination distinguishes phantom pregnancy alone from bacterial inflammation, as milk production does not always mean infection.

Can puppies continue nursing during treatment?

In some situations, puppies can nurse from healthy glands. If the mother is systemically ill or needs medicine unsuitable for nursing puppies, supplementary feeding or weaning is necessary. Your vet provides a plan based on the mother and the whole litter's situation.

Can milk from an inflamed gland look normal?

Yes. Milk can look normal despite inflammation. A sample is therefore taken from a suspect gland for culture even when no blood or pus is visible. Poor puppy growth may be the first sign of subclinical inflammation.

Do all mammary changes need antibiotics?

Not every enlarged or irritated gland indicates bacterial infection. Injury and prolonged milk accumulation can cause inflammation through other mechanisms. Treatment is chosen following a veterinary examination and any necessary samples, so do not start medication yourself.

How quickly does mastitis resolve?

With appropriate treatment, signs usually settle within 2–3 weeks. Severe gangrenous inflammation or sepsis worsens the outlook. At home, monitor both the mother's condition and the puppies' weight gain; a visible reduction in swelling does not replace agreed follow-up.