Clostridium Difficile in Dogs

Clostridium difficile, or C. difficile, is a bacterial pathogen that causes inflammation in the large bowels (colon) of some mammals. This inflammation is known as colitis. C. difficile is not normally present in the bowels of healthy dogs and in excessive numbers these bacteria can cause illness.

Causes and Transmission of C. difficile Infection

Infection occurs when there is both the presence of numerous C. difficile bacteria and a reduction of non-infectious bacteria that normally exist in the colon of a healthy dog. Reduction of normal bacteria is often caused by certain antibiotics and immunosuppressive drugs. These drugs may have been recently given during antimicrobial therapy for another unrelated infection. Without the presence of normal colonic bacteria, C. difficile is capable of growth within the colon. If it is already present in the dog's colon, or if the dog is exposed to the bacteria at this time, the colon can become host to an infectious number of the bacteria. This disease is also known as antibiotic associated colitits.

Dogs may also shed C. difficile in their feces without showing symptoms of infection. The bacteria is capable of surviving harsh environmental conditions by existing in a dormant spore form. These bacterial spores are difficult to clean or remove. Once ingested by a new host, they pass through the digestive system to the colon. In the colon spores can wake from the dormant state and begin to reproduce. Humans, particularly infants, are host to infectious C. difficile, but are not symptomatic. Transmission and effects of infection in dogs can vary depending on the quantity of bacterial spores in the environment, the level of exposure, and the general health condition and age of the exposed animal.

Symptoms of C. Difficile Infection and Associated Colitis

Symptoms of infection can range from mild diarrhea to severe acute colitis. Severity of symptoms is dependent upon the release of toxins by the bacteria. C. difficile produces two separate toxins that are called toxin A (enterotoxin) and toxin B (cytotoxin). Both toxins cause damage to the cells and tissue of the colon, resulting in inflammation and lesions. Visible symptoms exhibited by an infected dog include:

  • Diarrhea
  • Blood in stool
  • Mucus in stool
  • Straining during elimination
  • Painful elimination
  • Weakness
  • Reluctance to walk
  • Abdominal pain
  • Dehydration
  • Excessive water consumption

Diagnosis of C. difficile Infection and Associated Colitis

Laboratory tests and x-rays can determine if a dog is suffering from colitis. Determining if the colitis is due to an infection of C. difficile requires isolation of the toxins the bacteria releases. For this purpose a veterinarian may recommend laboratory tests such as a bacterial culture, a fecal culture or a cell culture to determine if the toxins released by C. difficile are present.

Treatment of C. Difficile Infection and Associated Colitis

The antibiotic that was previously administered is likely to be responsible for the associated colitis. This antibiotic should no longer be given and should be replaced with one that is effective against C. difficile, such as metronidazole.  A veterinarian may recommend a prescription diet to aid in digestion and replenish essential nutrients. The dog must be allowed constant access to clean, fresh water. Activity should be restricted to limited walks with the dog on a leash at all times.