Inflammation of the Mammary Gland in Guinea Pigs

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Mastitis in Guinea Pigs

Mastitis is a condition in which there is inflammation of the mammary glands (milk glands), mostly due to infections with bacterial pathogens. Mastitis often occurs during the period when a female guinea pig's (also called a sow) offspring are suckling. Trauma, like cuts or scrapes to the mammary tissue, is one of the known causes of bacterial infections that can lead to mastitis.

Mastitis is a painful and serious condition, and without prompt treatment, the bacterial infection may spread to the sow's bloodstream, leading to other more severe complications.

Symptoms and Types

Mammary tissues may become:

  • Swollen, red (inflamed) and tender
  • Warm to the touch
  • Enlarged and painful
  • Bluish in color
  • or excrete thick, bloody or clotted milk

Complications due to mastitis may also lead to a life-threatening systemic infection. Signs of this include:

  • Fever
  • Loss of appetite
  • Dehydration
  • Depression
  • Lack of milk supply


Mastitis is usually caused by a bacterial infection that has entered the tissue of the milk glands, either through the milk ducts or through an abrasion to the skin. This type of infection is most commonly seen during the period when the sow is nursing a litter of young. The sow is at higher risk when she is ill, undernourished, dehydrated, or is under stress.


Newborn guinea pigs are born with their teeth intact, so it is possible that a minor abrasion to the mother's skin can take place as the result of normal nursing. The abrasion then becomes an open point of entry for bacteria, leading to mastitis, or infection, of the milk glands. For this reason, the mammary glands of the nursing sow should be observed frequently for injuries that may have been caused by the suckling of the newborns.

If the symptoms (listed above) of mastitis are present, the chance is good that your guinea pig has an infection, and will need to be seen by a veterinarian before the infection has an opportunity to infect the bloodstream, or before the milk ceases to flow and the pups die from malnutrition.

A diagnosis of mastitis can be determined by a combination of the history you are able to provide to your veterinarian, and by the symptoms that are observed. A sample of milk or fluid from the affected area can usually confirm the suspicion of mastitis. Blood tests may also be necessary for determining the exact nature of the infectious agent that is causing the condition, and the severity of the infection on the body, so that appropriate treatment can be provided.

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