Lumpy Jaw (Actinomycosis) in Hamsters

By PetMD Editorial on Jul. 7, 2010

Actinomycosis is a rare infectious disease caused by gram positive, rod-shaped bacteria of the genus Actinomyces; more specifically, the A. bovis species. This bacterium is a common inhabitant of a hamster's mouth. It is only when the animal has an open wound in the mouth that the bacteria is able to enter the bloodstream and cause a widespread infection. This can lead to inflammation and softening of the jawbones, hence the more common name of the disease: “Lumpy Jaw.”


In the initial stage of actinomycosis, the hamster experiences respiratory difficulties. The heart rate and pulse rate will increase, and the skin may become bluish. In the later stages, pus-filled pockets (abscesses) inside the salivary glands will burst, causing swelling, especially in the jaw region. The jaws will become swollen until the hamster is unable to eat, which leads to weight loss.


Actinomycosis in hamsters is due to the bacteria Actinomyces bovis, which gains entry into the body through wounds present in the mouth.


You will need to give a thorough history of your hamster’s health, including the onset and nature of the symptoms, to the veterinarian. He or she will then perform a complete physical examination.

For a more definitive diagnosis your veterinarian will submit a specimen of pus for culturing. Gram staining, cytology, and acid-fast staining may also be employed.


Your veterinarian will attempt to lance and drain the abscess(es). In addition to sodium iodide, which is given orally, there are some antibiotics that are thought to be effective in treating actinomycosis in hamsters. Consult your veterinarian for the best course of treatment in your hamster's case.

Living and Management

While recovering from actinomycosis, the hamster must be separated from other hamsters and housed in a clean and calm environment. Its diet should consist of soft foods that are easily chewed and digested. You may even want to first mash the food.


Isolation of an infected hamster and providing prompt treatment helps in preventing the spread of this bacterial infection to other pets.

Featured Image: Sezer

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