When pets get chronic diarrhea, one of the tests that sooner or later comes up is the test for Clostridium perfringens enterotoxin. Clostridium perfringens is a bacterium and it produces an unpleasant toxin. The situation sounds simple: one gets infected with toxin-forming bacteria, one gets diarrhea, the diarrhea should at least improve with removal of the toxin-forming bacteria. As with most things, the situation turns out to be more complicated.
Clostridium perfringens is one species out of numerous Clostridia. Clostridial diseases are very classic in medicine, both veterinary and human. It is a Clostridium that causes tetanus, a Clostridium that causes botulism, and Clostridia are responsible for gangrene, “black leg,” lamb dysentery and other famous maladies. Clostridia have several features in common that make them especially nefarious but most importantly:
- They produce toxins.
- They are anaerobic (they grow in the absence of oxygen).
- They form spores (essentially armor) so as to withstand environmental change (including disinfectants) that would kill more vulnerable bacteria.
Clostridium perfringens is one of the brothers of this evil family and is further classified into five types depending on what combination of four toxins it produces.
One of the toxins that some Clostridium perfringens strains can produce is called Clostridium perfringens enterotoxin. It causes fluid secretion into the intestine and this leads to diarrhea. This toxin can be detected in 34% of dogs with diarrhea (and 5 - 14% of dogs that don’t have diarrhea).
This is the crux of the problem. Clostridium perfringens can be cultured from the feces of 80% of dogs whether they have diarrhea or not. Plus, we know that while C. perfringens enterotoxin certainly causes diarrhea, some dogs seem to be unaffected.
The organism can be consumed in food and when it arrives in the small intestine, it sporulates (forms a spore) and begins to produce its toxin. Alternatively, the organism may have been happily and innocuously living in the intestine for who knows how long when something causes it sporulate and produce toxin. The trigger may be dietary, related to infection with another organism or even related to the administration of a medication. The type of diarrhea produced by the toxin is generally a colitis, meaning the large intestine is affected. Such types of diarrhea are mucous, possibly bloody, and associated with straining. A more watery diarrhea (as comes from the small intestine) is also possible. Severity of the diarrhea can be mild all the way to life-threatening.
Let us begin with the obvious: a dog does not need to be treated for Clostridium perfringens unless it has diarrhea. Since 80% of dogs harbor Clostridium perfringens whether they have diarrhea or not, culturing Clostridium perfringens from a fecal sample will not be adequate for diagnosis; we have to find the toxin.
In the past, looking under the microscope for Clostridial spores was thought to be helpful, since we know the organism must change to its spore-form to produce toxin. Apparently, the organism sporulates without necessarily producing toxin so this method has not been as helpful as we had hoped.
Immunologic testing for the presence of the toxin in a fecal sample is the state of the art at the current time. These tests are performed at a reference laboratory and results are typically obtained in 1 - 2 days. For maximum accuracy, PCR testing for detection of the Clostridial gene for enterotoxin production is combined with the above immunologic testing for toxin presence.
Any number of antibiotics can be used to remove Clostridium perfringens. Some choices include: ampicillin, amoxicillin, metronidazole, erythromycin, and tylosin. Tetracycline was formerly on the list but too much resistance has developed. If Clostridium perfringens is responsible for the diarrhea, a response to antibiotics is generally seen in a couple of days. A total antibiotic course of several weeks is typical.
Page last updated: 2/1/2012