Intestinal Diseases - The Merck Veterinary Manual

Intestinal Diseases

Intestinal disease is a major cause of death in young rabbits. Although most diarrheal diseases were once lumped together (as the enteritis complex) or simply called mucoid enteritis, specific diseases are being delineated. Diet, antibiotic treatment, and other factors create disturbances of the GI microflora and may predispose rabbits to dysbiosis and intestinal disease. For discussion of hairballs, see Hair Chewing and Hairballs.

Enterotoxemia:

Enterotoxemia is an explosive diarrheal disease, primarily of rabbits 4-8 wk old. It occasionally affects adults and junior stock. Signs are lethargy, rough coat, a perineal area covered with greenish brown fecal material, and death within 48 hr. Often, a rabbit looks healthy in the evening and is dead the next morning. Necropsy reveals the typical lesions of enterotoxemia, ie, a fluid-distended intestine with hemorrhagic petechiae on the serosal surface. The primary causative agent is Clostridium spiroforme , which produces an iota toxin. Little is known about transmission of the organism; it is assumed to be a commensal that is normally present in low numbers. The type of diet seems to be a factor in development of the disease; enterotoxemia is seen less often when high-fiber diets are fed. Because lincomycin, clindamycin, and erythromycin induce Clostridium -related (eg, C difficile ) enterotoxemia due to their selective effect on normal gram-positive bacteria, they are contraindicated in rabbits. Enterotoxemia is a consideration for most antibiotic therapy, and it has been seen after administration of penicillins and cephalosporins. The incidence rate is 40-80% after oral penicillin therapy, which should be considered contraindicated in rabbits. These diarrheas are remarkably similar to those that occur naturally (described above as enterotoxemia). Treatment of colony rabbits is seldom attempted because of the rapidity of death. However, when population size permits, cholestyramine has been used with promising results, both as a preventive and a treatment. Reducing stress of the young rabbits (weaning, etc) and ad lib feeding of hay or straw are helpful in prevention. Adding 250 ppm of copper sulfate to the diet of young rabbits also helps prevent enterotoxemia. Individual animal treatment for enterotoxemia should include supportive fluid therapy. There is little evidence that antibiotics are helpful. Diagnosis depends on history, signs, lesions, and demonstration of C spiroforme . Centrifugation of intestinal contents at 20,000 g for 15 min followed by culture of the supernatant-pellet interface will reveal the organism. For a definitive diagnosis, the presence of iota toxin in the supernatant of centrifuged cecal contents can be demonstrated by in vivo or in vitro assays.

Tyzzer’s Disease:

Clostridium piliforme, liver section

Tyzzer’s disease ( Tyzzer’s Disease: Introduction), caused by Clostridium piliforme (formerly Bacillus piliformis ), is characterized by profuse watery diarrhea, anorexia, dehydration, lethargy, staining of the hindquarters, and death within 1-3 days in weanling rabbits 6-12 wk old. Acute outbreaks have been associated with >90% mortality. Some rabbits may develop chronic infections that present clinically as a wasting disease. Infection occurs by ingestion and is associated with poor sanitation and stress. The lesions consist of necrotic enteritis along with multifocal necrosis in the liver and heart. Diagnosis is made histologically; special stains (eg, Giemsa or Warthin-Starry silver) show the characteristic intracellular bacterium. Culturing is impractical because the bacterium does not grow on artificial media. Serologic tests are available from laboratory animal diagnostic laboratories. Tyzzer’s disease affects a wide spectrum of other species but has not been reported in humans, although titers have been documented in pregnant women. Although antibiotics used in treatment of other animals have not been effective in rabbits, oxytetracycline has been of some value in limiting an outbreak. No vaccine is available. Aggressive disinfection and decontamination of the housing facility to reduce the presence of hardy spores is indicated with either 1% peracetic acid or 3% hypochlorite.

Colibacillosis:

Escherichia coli as a cause of rabbit diarrhea has been confused by the circumstance that E coli often proliferate when rabbits develop diarrhea for any reason. Enteropathogenic strains of E coli (serotype O103) commonly express the eae gene, which codes for intimin, an outer membrane protein associated with the attaching and effacing lesions. Serotypes O15:H, O109:H2, O103:H2, O128, and O132 are also important. Normal healthy rabbits do not have E coli of any strain associated with their GI tract.

Two types of colibacillosis are seen in rabbits, depending on age. Rabbits 1-2 wk old develop a severe yellowish diarrhea that results in high mortality. It is common for entire litters to succumb to this disease. In weaned rabbits 4-6 wk old, a diarrheal disease very similar to that described for enterotoxemia is seen. The intestines are fluid filled, with petechial hemorrhages on the serosal surface, similar to the pathology described for both Tyzzer’s disease and enterotoxemia (see above). Death occurs in 5-14 days, or rabbits are left stunted and unthrifty. Diagnosis is made by isolating E coli on blood agar and then having the isolate biotyped or serotyped. Electron micrographs of E coli attached to the mucosa are also helpful. In severe cases, treatment is not successful; in mild cases, antibiotics are of value. Severely affected rabbits should be culled, and facilities thoroughly sanitized. High-fiber diets appear to help prevent the disease in weaned rabbits.

Proliferative Enteropathy:

Proliferative enteropathy caused by Lawsonia intracellularis has been reported to cause diarrhea in weanling rabbits. Clinical symptoms include diarrhea, depression, and dehydration, which resolve over 1-2 wk. Disease does not cause death unless associated with a dual infection with another enteropathogenic agent. Diagnosis is based on necropsy findings of a thickened and corrugated ileum and histologic identification of the rod-shaped to curved or spiral silver-staining organism in crypt enterocytes. The organism requires cell-containing media (enterocytes) for culture. Immunohistochemistry and PCR may be useful to identify L intracellularis . Isolation of sick animals and symptomatic treatment is advised.

Mucoid Enteropathy:

Mucoid enteropathy is a distinct diarrheal disease of rabbits, characterized by minimal inflammation, hypersecretion, and accumulation of mucus in the small and large intestines. While the etiology is unknown, it may occur concurrent with other enteric diseases. Predisposing factors include dietary changes, dietary fiber <6% or >22%, antibiotic treatments, environmental stress, and challenges with other bacteria. Clinical signs are gelatinous or mucus-covered feces, anorexia, lethargy, subnormal temperature, dehydration, rough coat, and often a bloated abdomen due to excess water in the stomach. A firm, impacted cecum may be palpable. The perineal area is often covered with mucus and feces. Diagnosis is based on clinical signs and necropsy findings of gelatinous mucus in the colon. Rabbits may live for ~1 wk. Treatment is unrewarding, but intense fluid therapy, enema removal of mucus mass, antibiotics, and analgesics may be tried. Prevention is the same as for any rabbit enteropathy.