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.

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.

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.

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

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

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.

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.

• Antibiotics
• Surgery