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Anaerobic Bacterial Infections in Dogs

Anaerobic infections involve bacteria that thrive best in environments devoid of free oxygen. They commonly proliferate in areas like the gums around the mouth, deep wounds resulting from skin punctures, fractures where bone breaks through the skin, and deep bite wounds inflicted by other animals. Slow wound healing may indicate the presence of anaerobic infection.

While anaerobes naturally coexist within the body’s ecosystem, inhabiting regions such as the abdomen, vaginal canal, intestines, and mouth in symbiosis, disruptions to bacterial balance due to surgery, deep injuries, or internal infections can prompt these bacteria to invade tissue in dogs. This invasion can result in deep infection and tissue necrosis. Without proper treatment, anaerobic infections can progress to shock and potentially fatal outcomes.

Symptoms and Types

The symptoms of anaerobic infections in dogs vary depending on the underlying cause. Dogs afflicted with anaerobic bacterial infections due to wounds may exhibit bite marks, discharge of pus from the wound, or open fractures where bone protrudes. Additionally, wounds infected with anaerobic bacteria tend to heal slowly. Other prevalent symptoms of anaerobic bacterial infections in dogs encompass fever, limping, difficulty in eating, and diminished appetite, particularly when the gums are infected.

Several types of bacteria can instigate these infections, including:

  • Bacteroides
  • Fusobacterium
  • Actinomyces
  • Clostridium
  • Peptostreptococcus


The primary cause of an anaerobic bacterial infection in dogs stems from the disturbance of the normal bacterial equilibrium within their bodies. Such disruptions often arise from deep injuries, trauma, or recent surgical interventions, such as abdominal surgery or the placement of metal implants to stabilize broken bones.


Providing your veterinarian with a comprehensive history of your dog’s health, symptom onset, and potential incidents that could have triggered the condition is essential. This includes detailing any injuries, even minor ones, as well as any recent altercations with other animals, difficulties with eating (potentially related to oral infections), and recent surgical procedures. Before confirming an anaerobic infection, your veterinarian will need to eliminate other potential causes.

Standard diagnostic tests comprise a chemical blood profile, a complete blood count, and a urinalysis, any of which might reveal an elevated white blood cell count or indications of a systemic infection. Your veterinarian will obtain samples of pus and tissue (skin/muscle) from the affected area for laboratory culturing without oxygen. Growth in the culture may indicate the presence of anaerobic bacteria, confirming the diagnosis.


Your veterinarian will prescribe long-term antibiotics for your dog. Although it may be challenging to administer pills to your dog for weeks, it is crucial to complete the entire course of treatment, even if symptoms improve and your dog appears to be recovering. Any remaining infection, no matter how small, can potentially return in a more severe form. For dogs reluctant to take pills, many may accept them when hidden in a small amount of human food. If using this method, ensure that your dog has consumed the entire bite of food and has not hidden it away (e.g., behind a couch).

Specific treatment depends on the accessibility of the infection. If the infection is in reachable areas like muscles (e.g., legs, back, rump, neck), the veterinarian will surgically open the wound, remove dead tissue, and expose it to oxygen. However, if the anaerobic infection is internal, such as within the uterus, bones, or abdomen, the veterinarian will need to anesthetize the dog for surgical intervention to open, clean, and/or drain the affected areas.

Living and Management

Anaerobic infections typically require prolonged treatment with antibiotics and regular monitoring by a veterinarian. It’s crucial to administer antibiotics to your dog as instructed by your veterinarian and on schedule. If bandaging is necessary, ensure that you understand the cleaning and redressing procedures advised by your veterinarian to facilitate wound healing. You might need to use an Elizabethan collar or cone to prevent your dog from interfering with the wound.

Regular follow-up appointments are essential for wound assessment and potential reopening and cleansing if needed. Biochemical profiles will be repeated during these visits to monitor the infection’s progress. Between appointments, contact your veterinarian promptly if you observe any changes in your dog’s behavior, such as increased fatigue, loss of appetite, or signs of inflammation, such as redness, swelling, or pus at the wound site.

During the healing process, consider avoiding certain activities like swimming and limiting your dog’s outdoor time to prevent contamination of the infected area.

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