Clostridial Overgrowth & Enterotoxicosis in Dogs
What is clostridial enterotoxicosis in dogs?
Clostridial enterotoxicosis is a complex and poorly understood syndrome characterized by diarrhea that is associated with the bacteria Clostridium perfringens (CP). “Clostridial” refers to the Clostridium bacteria, “entero” refers to the intestines, and “toxicosis” is the medical term assigned to any condition caused by a toxin or a poison.
It is suspected that up to 15-20% of diarrhea cases in dogs are CP-related. While clostridial enterotoxicosis may occur in dogs of any age, most dogs who develop chronic signs are middle-aged or older.
What are the clinical signs associated with clostridial enterotoxicosis?
Clostridial enterotoxicosis is associated with either acute diarrhea that is typically self-limiting, lasting for 5-7 days, or chronic, intermittent diarrhea.
Acute clostridial enterotoxicosis typically causes sudden bloody stomach and intestinal inflammation called “acute hemorrhagic gastroenteritis.” The most common sign is large-bowel diarrhea with mucus, small amounts of fresh blood, small amounts of stool, and straining to defecate. These dogs feel a sense of urgency and attempt to defecate frequently. Some dogs may show signs of small-bowel diarrhea, which is characterized by large volumes of watery stool.
Chronic clostridial enterotoxicosis is characterized by intermittent episodes recurring every 4-6 weeks. These episodes may persist for months to years. Other signs include vomiting, flatulence, blood in the stool, abdominal discomfort, and general unthriftiness (failure to grow and develop normally). Most dogs do not have fever associated with clostridial enterotoxicosis.
What causes clostridial enterotoxicosis?
Clostridial enterotoxicosis is not caused by the bacteria directly, but rather by a toxin produced by the bacteria. Only certain strains of CP are able to produce the intestinal toxin that causes illness, and only certain dogs are clinically affected. It is unknown if the toxin-producing strain of CP is a true infection, or if the bacteria is normally in the dog’s intestinal tract and certain conditions – e.g. stress or dietary indiscretion – lead to production of the intestinal toxin that causes disease (making CP an opportunistic organism). In either case, clostridial enterotoxicosis is often associated with an excessive number of the CP bacteria in the small intestine. This is called “bacterial overgrowth.”
"Only certain strains of CP are able to
produce the intestinal toxin that causes illness,
and only certain dogs are clinically affected."
The ability of CP to cause disease may depend on the health of the gastrointestinal tract, including its metabolic, mucosal, and immunologic integrity. In some cases, a normal immunity-related protein in the intestinal tract is too low to be effective in protecting the intestinal tract from infection and/or the toxin. In other cases, a higher pH (more alkaline) within the intestinal tract promotes bacteria to produce spores and toxins.
How is clostridial enterotoxicosis treated?
Most cases of intestinal bacterial overgrowth are treated on an outpatient basis, although if vomiting and diarrhea are severe, the dog may require hospitalization for fluid and electrolyte therapy to replace losses.
Nutrition plays a role in the treatment and management of pets with chronic recurring clostridial enterotoxicosis. Higher fiber diets often improve clinical signs by reducing the number of clostridial bacteria in the intestinal tract and by lowering the pH in the intestine (acidifying the environment), and limiting the production of spores and toxins of CP. Psyllium is a source of soluble fiber that may be used to enhance the fiber-related effects of commercially available high-fiber diets. Another appropriate nutritional option may be a prebiotic diet that contains fermentable substances – e.g. fructo-oligosaccharides – that can influence the make-up of the bacteria in the intestinal tract.
Acute, self-limiting clostridial enterotoxicosis usually requires antibiotic treatment for 5-7 days. Chronic recurring cases often require prolonged antibiotic therapy, and may need tylosin (a poultry antibiotic that provides anti-inflammatory effects in the dog’s intestine) mixed with the food or formulated in capsules.
High doses of antibiotics may not be needed to prevent clinical recurrence in cases of chronic clostridial enterotoxicosis. Lower doses of antibiotics may not reduce the number of CP bacteria in the intestine, but may change the intestinal environment, preventing the bacteria from producing spores and toxins.
Probiotics may also have beneficial antibacterial effects on Clostridium.
What sort of follow-up is best for dogs with clostridial enterotoxicosis?
Most dogs respond well to long-term management if it’s needed. If clostridial infection is associated with environmental contamination, then disinfecting the environment is difficult. Feeding high-fiber diets may decrease the incidence of diarrhea. If treatment of suspected clostridial enterotoxicosis fails, this suggests the presence of other existing disease conditions and additional diagnostic evaluations are needed.
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