Published on
Last updated on
5 min read

Key takeaways

Actinomycosis is a type of bacterial infection caused by a variety of Actinomyces species bacteria.

  • Actinomyces bacteria are commonly found in the mouth and are harmless unless they are introduced into deeper tissues through an open cut or puncture wound
  • A break in the skin caused by an object like a stick, thorn, or grass awn that’s contaminated with these bacteria can lead to a deep abscess or infection
  • Infection by Actinomyces often presents as a mass under the skin that may drain fluid through a small hole in the skin
  • Other generalized symptoms such as lethargy and decreased appetite may also be present
  • It is possible to specifically diagnose actinomycosis through bloodwork, but this type of diagnostic test usually isn’t necessary
  • Most abscesses and infections heal quickly with a generalized approach to therapy
  • Treatment is often successful with surgical removal of the damaged tissue and antibiotics
Are you concerned?

Connect with a vet to get more information about your pet’s health.

Book an online vet

A closer look: Actinomycosis in Dogs

Actinomycosis refers to any type of infection where Actinomyces bacteria have been identified. Dogs may become infected with this bacteria through penetrating wounds.

Actinomyces bacteria cannot penetrate healthy skin on their own. Once they’re pushed into deeper tissues as the result of an injury, they may proliferate and cause a severe infection.

Many cases of actinomycosis present as infected wounds or abscesses. These abscesses are commonly found around the face and neck, but they may appear anywhere a penetrating injury has occurred.

Connect with a vet to get more information

With DVM, ICH certifications and great reviews by pet parents like you for this symptom

Risk factors

Actinomycosis is rarely diagnosed in dogs. Most pet owners do not have to worry about it. Although it is uncommon, dogs who get in a fight or receive a puncture or bite wound are most at-risk of developing this type of infection. Hunting dogs as a group are also more likely to develop actinomycosis than dogs who do not perform this type of work.

If left untreated or undetected, more serious cases can develop. The original wound in the skin may have been tiny, albeit deep, and might have healed completely before symptoms of internal illness develop.

If the wound is confined to a small area just under the skin, it is much less likely to cause severe signs of illness. If the initial wound is deep and enters the chest cavity, the subsequent infection in the space around the heart and lungs can be life threatening. Symptoms vary depending on the location and severity of the wound and infection.

The severity of the infection itself can range from mild to severe, and the impact of infection varies depending on its location. When a wound is small and the infection is not spreading, a dog with actinomycosis is not likely to develop serious secondary symptoms. Instead, the wound won’t heal quickly and will show straightforward signs of infection like redness, swelling, and drainage. If the wound is larger and the infection spreads throughout the body, the dog will show generalized signs of illness.

Possible causes

Actinomycosis can only be caused by a puncture wound that has been contaminated with this bacteria. The contamination can originate from inside the infected dog’s own mouth or it may have been transmitted by whatever object or animal caused the wound. The presence of these bacteria in the mouth doesn’t cause disease or infection on its own.

Main symptoms

Actinomycosis generally presents as abscesses or sores in or under the skin (especially around the face and neck).

Testing and diagnosis

Veterinarians generally do not need to take the time to diagnose actinomycosis specifically, since generalized treatment strategies for infections are usually effective. A vet will decide how aggressively to pursue a diagnosis based on the severity of symptoms and response to therapy. Diagnostic tests may include, but are not limited to:

  • Blood tests
  • X-rays
  • Fluid analysis
  • Ultrasound

Steps to Recovery

Surgical intervention and medication are usually both necessary to treat infected wounds, including cases of actinomycosis. Antibiotics are prescribed to fight the infection and surgery is performed to remove masses, drain abscesses, or cut away infected tissue. A long course of antibiotics is usually required to effectively resolve actinomycosis.

Treatment may be required for weeks or even months after visible signs of infection have improved. With aggressive treatment, cure rates of up to 90% have been reported. Relapse is common, with up to 40% of dogs experiencing a recurrence.


Actinomycosis is only transmitted when wounds are contaminated with Actinomyces bacteria. As these bacteria are present in the mouths of healthy animals without causing disease, this is a perfect example of a disease that is infectious in nature, but not contagious. Actinomycosis does not spread from pet to pet or from pet to person without being introduced to deeper tissues because of a wound.

Is Actinomycosis in Dogs common?

Actinomycosis is rarely diagnosed, as most veterinarians proceed with generalized treatment of infected wounds without a specific diagnosis. Rates of penetrating wound infection vary based on lifestyle and geography.

Typical Treatment

  • Antibiotics
  • Surgery

Our editorial committee

Our medical review team is responsible for validating and maintaining the quality of our medical information.