Chronic large bowel diarrhea in dogs: What's new? (Proceedings) - Veterinary Healthcare


Chronic large bowel diarrhea in dogs: What's new? (Proceedings)


Clostridum perfringens enterotoxicosis

Acute and chronic large bowel diarrhea has been associated with Clostridium perfringens type A enterotoxin. Vomiting, weight loss, flatulence, and abdominal pain occur less frequently. The disorder occurs most commonly in dogs. Both naturally occurring and hospital acquired cases have been detected. Diagnosis is commonly based on finding increased numbers of spores in rectal cytology specimens, or demonstrating the toxin in the feces (which is primarily done at referral hospitals). The reason for including this syndrome within this discussion of chronic idiopathic large bowel diarrhea is that in the author's hospital approximately 25% of toxin positive cases are negative on rectal cytology. Thus, in practices in which toxin is not analyzed, a case of Clostridium perfringens could easily be diagnosed as idiopathic. If fecal toxin cannot be routinely tested in a private practice, it may be indicated to treat a dog with chronic large bowel diarrhea with an appropriate antibiotic as described below to eliminate the presence of C. perfringens enterotoxicosis.

Diagnosis can be confirmed by identifying enterotoxin in a fecal sample. Most commonly this was done with a reverse latex agglutination test (PET-RPLA Kit, Oxoid USA, Columbia MO). However, the test is not available at the present time. An ELISA test (Clostridium perfringens Enterotoxin Test, TechLab, Blacksburg, VA) is now being used in the author's hospital, but we have not had enough experience to comment on test results. Diagnosis should be suspected when greater than 3-5 spores per oil immersion field are found in a rectal cytology specimen. The spores are larger than most bacteria and assume a "safety pin" appearance. However, a preliminary study has recently shown a poor relationship between fecal toxin and spores in rectal cytology samples.

A vegetative form of C perfringens is a normal inhabitant of the colon. The enterotoxin is a component of the spore coat and causes intestinal fluid accumulation, mucosal damage, and diarrhea. The stimuli for sporulation and enterotoxin production are unknown. Enterotoxin has also been identified in some cases of hemorrhagic gastroenteritis syndrome (HGE), parvovirus, giardiasis, and IBD. The author has also demonstrated toxin in the feces of dogs without diarrhea!

This syndrome is controversial and not all authors accept the clear description of the clinical presentation presented above. Several epidemiologic studies looking at groups of dogs with diarrhea, sick hospitalized dogs without diarrhea, and healthy outpatients have not found a difference between these groups in the percentage of dogs that are positive for fecal enterotoxin. Some of this data was obtained with the reverse passive latex agglutination test (RPLA), which is no longer available. An additional study using the currently available ELISA test did find that more dogs with diarrhea were positive for fecal enterotoxin than controls. In addition, these epidemiologic studies also found a poor relationship between the presence of fecal enterotoxin and endospores in rectal cytology samples in dogs with and without diarrhea.

Until a universal description of this syndrome emerges, the author suggests that a diagnosis should be confirmed by identifying enterotoxin in a fecal sample. An ELISA test (Clostridium perfringens Enterotoxin Test, TechLab, Blacksburg, VA) is currently available at commercial and Veterinary Diagnostic laboratories. However, a recent study utilizing the RPLA showed that there were 14% discordant results in dogs with diarrhea after feces were either refrigerated or frozen for 24 hours when compared to immediate analysis. Until a similar study is performed with the ELISA test, this study suggests that shipment of refrigerated or frozen feces to a laboratory could lead to erroneous results. In cases with typical signs of large bowel disease without GI parasites or dietary indiscretion, diagnosis should be suspected when greater than 3-5 spores per oil immersion field are found in a rectal cytology specimen if enterotoxin analysis cannot be performed. A recent study showed that in dogs with diarrhea, there was a relationship between large bowel signs and spore numbers.

Acute cases may resolve spontaneously. Chronic cases respond to antibiotic therapy in 3-5 days. Metronidazole at 6 mg/kg BID-TID for 7 days is often effective. Ampicillin 22 mg/kg PO TID or amoxicillin 11-22 mg/kg PO BID-TID are also effective treatments. Cases that show intermittent clinical signs require long term therapy. Tylosin can be used in these cases at 10-20 mg/kg BID. Some cases respond to feeding a high fiber diet.

The prognosis is excellent. Most affected animals respond to therapy within several days. Clinical findings have not been identified that predict which animals need long-term therapy.


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