Clinical Signs

Gastrointestinal symptoms can be either acute or chronic with signs in chronic cases lasting up to 5 months. Most dogs with acute clostridial enterotoxemia exhibit signs of large bowel diarrhea, as enterotoxin damages the distal small intestine and proximal colon. Fecal mucus, fresh blood, scant stools, tenesrnus and increased frequency of defecation are characteristic. Some dogs may have only mucoid stools while others may present with clinical signs of small bowel diarrhea characterized by large volumes of watery stool. The duration of an acute episode is approximately 3-5 days. Chronic disease may fluctuate occurring every few weeks and lasting for several days. Vomiting may or may not be present and fever is seldom observed.

Enterotoxemia has been identified with con- current diseases such as hemorrhagic gastroenteritis syndrome (HGE), parvovirus enteritis, giardiasis and other causes of inflammatory bowel disease. Such concurrent disease, as well as dietary changes and stress may all predispose to the condition.

Pathogenesis

Enterotoxigenic Clostridium perfringens strains produce clinical signs in an overgrowth situation. Enterotoxin production exerts its effect locally and directly on the intestinal epithelium causing secretion of protein and electrolyte-rich fluid into the intestinal lumen. Eventual necrosis and sloughing of the mucosal epithelium occurs weakening intestinal peristalsis.

Clostridium perfringens is a normal enteric bacterium found predominantly in a vegetative, non-enterotoxin producing form. Under certain conditions, the organism undergoes enteric sporulation at which stage the enterotoxin is released. The organisms tend to colonize the distal small intestine and upper colon and sporulation is favored in an alkaline environment.

Nutritional changes, alteration of bacterial microflora, decreased local IgA immunity and intestinal epithelial injury may all play a role in initiating the spore forming change in the strains of clostridium that produce this disease.

Incidence

Studies at Colorado State suggest that this form of enterotoxemia may account for up to 15% of dogs that present with gastrointestinal disease.

Diagnosis

Since Clostridium perfringens is a normal intestinal inhabitant, anaerobic fecal cultures for the organism alone are not diagnostic. Direct smear cytology to identify high numbers of spore forming clostridial organisms serves as a simple rough screening test. Two thin, air dried smears of fecal material can be submitted for Direct Smear Cytology, Test Code #5249. The smear is stained and checked for the presence of a high percentage of spore forming clostridial organisms. Spore counts of greater than 5 per high power oil immersion field are considered as suggestive, however, the absence of spores does not rule out the diagnosis. Definitive diagnosis is based on identifying the enterotoxin in the feces. The test requires 3-5 grams of fecal material submitted on ice. Submit as Test Code #16007 Clostridium perfringens Enterotoxin (CLOE).

Treatment

Most acute cases respond well to fluids and oral antibiotic therapy directed against Clostridium perfringens. Ampicillin, amoxicillin, tylosin, clindamycin or high dose metronidazole therapy have been recommended.

Chronic cases require long term antibiotic use and/or diet manipulation using high fiber con- tent diets. Fiber has been shown to alter colonic bacterial microflora and maintain a more acidic pH. These changes inhibit clostridial spore formation. Soluble fiber supplements such as psyllium can also be used.

As a diagnostic technique, rectal swabs are most informative when a diffuse disease process affects the lamina propria of the colorectal region (see Table).

Rectal mucosal scrapings are indicated when signs of large bowel disease are present. Such signs include tenesmus, increased fecal mucus or hematochezia.

The technique of rectal mucosal scraping utilizes a rigid spatula such as a conjunctival scraper, ear curette or chemistry spatula. The overlying epithelium is scraped to collect inflammatory or neoplastic cellular infiltrate and/or pathogens from the surface of the rectal mucosa. While cotton tipped applicators can be used, they usually are not abrasive enough to obtain an adequate cytologic specimen.

Feces within the rectum are removed, and the instrument is guided into position with a gloved fin- ger. Lubricant should not be used. The instrument is drawn across the mucosa several times with enough pressure to denude the superficial epithelium. The sample is then smeared onto glass slides in a rotating fashion concentrating the material in the center of the slide in an area of about 1 cm square. Two to three air dried, unfixed smears should be submitted. Check the Test Request Form for "Cytology, Direct Smear, Source – Rectal Mucosa". Please include an appropriate history.

• bacterial colitis
• eosinophilic colitis
• lymphocytic/plasmacytic enteritis
• chronic ulcerative colitis
• histoplasmosis
• protothecosis
• protozoal infections
• clostridial sporulation

Recognized bacterial pathogens that can induce chronic diarrhea in dogs and cats include: enteropathogenic Escherichia coli, and salmonella, campylobacter, yersinia and shigella species. The detection and differentiation of these organisms requires specific culturing techniques using selective broths and agars, along with specific atmospheric and temperature controls. For example, the isolation of Campylobacter jejuni requires microaerophilic conditions and an incubation temperature of 42-C for 48 hours on a selective agar medium.

Fecal or rectal swabs should be submitted for this test. Check the Test Code #4300, Fecal Culture; ID only, Test Code #3906.

Protozoal organisms such as isospora, giardia and cryptosporidium (in immune deficient animals) species also can be diagnosed using specific testing techniques. Isospora organisms usually are detectable on a routine fecal smear. Giardia may or may not be detectable using this technique, however the ELISA method that detects antigen present in the stool has proven more reliable and accurate in detecting this pathogen. Cryptosporidium are detected by acid- fast or immunostaining techniques performed on a fecal smear (please specify if you wish to test for this organism).