JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
September 2021
D-M04
SIGNALMENT (JPC #2316884): A young New Zealand white rabbit
HISTORY: The animal was depressed, displayed a crouched stance, grinding of the teeth, thin conformation, bloated abdomen and had diarrhea.
HISTOPATHOLOGIC DESCRIPTION: Colon: The colonic lumen is markedly distended and contains abundant amphophilic, flocculent to fibrillar material (mucus). Approximately 95% of the mucosal epithelium is thickened up to twice normal by tortuous, hyperplastic crypts that are lined almost entirely by hyperplastic and hypertrophied goblet cells. Crypt lumina are occasionally expanded with mucus. Multifocally there are few, small aggregates of lymphocytes and plasma cells within the lamina propria.
MORPHOLOGIC DIAGNOSIS: Colon: Goblet cell hyperplasia, diffuse, severe, with abundant intraluminal mucus accumulation, New Zealand white rabbit, lagomorph.
CONDITION: Mucoid enteropathy (ME)
GENERAL DISCUSSION:
- Major disease of domestic rabbits, Important cause of mortality in rabbit production and research facilities
- Most affected are weanling rabbits between 7-10 weeks of age
- Morbidity and mortality can be high
PATHOGENESIS:
- Cause is unknown, many proposed theories; toxin-induced secretory disease occurring secondary to constipation and impaction
- Proposed theory: Higher incidence with high carbohydrate/low fiber diet: Low dietary fiber > ↓cecal acetate > cecal acidification > changes in microflora / ↑ harmful opportunistic bacteria, decreased ciliated protozoa, metachromatic bacilli (dysbiosis) > bacterial toxins released (secretagogues) > stimulate intestinal goblet cell hyperplasia
- Dysautonomia has been documented in rabbitries affected with this condition
- Often associated high carbohydrate/low fiber diet
- May precede or be associated with viral and/or bacterial intestinal conditions
- Often associated with bacterial dysbiosis
- Sterile cecal contents from affected rabbits produce goblet cell hyperplasia in other rabbits, confirming the presence of an unknown secretagogue (possible endogenous substance or toxin)
- Cardinal features include gastric bloat, mucus discharge and cecal impaction; these are considered non-specific responses of the rabbit intestine to many causes
TYPICAL CLINICAL FINDINGS:
- Acute, fatal cases follow a 2-4 day course
- Bruxism, anorexia, lethargy, crouched stance, diarrhea, succession splash, cecal impaction, abundant clear gelatinous mucus in colon
- Cecal impaction and colonic mucus accumulation, 7-14 days post onset of syndrome
- Elevated hematocrit, RBC count, hemoglobin, and BUN
- Decreased sodium, chloride, and phosphorous
- Stress induced heterophilia and hyperglycemia
TYPICAL GROSS FINDINGS:
- 3 cardinal features (non-specific; responses to unknown deleterious factors)
- Gastric bloat: Stomach is often distended with gas and fluid
- Mucus discharge: Colon distended with clear, gelatinous mucus
- Cecal impaction: Cecum often compacted with dry content
- Small intestines generally contain watery, bile-stained contents; jejunum may be distended
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Goblet cell hyperplasia may be present throughout the gastrointestinal tract and is most severe and consistent in the ileum and colon; minimal to absent lesions in cecum
- Marked mucin discharge into intestine lumen with mucin distended crypts
- The absence of inflammation is characteristic
ADDITIONAL DIAGNOSTIC TESTS:
- Diagnosis is based on clinical signs and characteristic gross and microscopic features
COMPARATIVE PATHOLOGY:
- ME has similarities to human cystic fibrosis, a disease of defective electrolyte transport that causes excessive mucus production by intestines, pancreatic and bile ducts, and respiratory epithelium
REFERENCES:
- Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016:306-307.
- Haligur M, Ozmen O, Demir N. Pathological and ultrastructural studies on mucoid enteropathy in New Zealand rabbits. J Exotic Pet Med. 2009; 18:224-228.
- Hotchkiss CE, Merritt AM. Mucus secretagogue activity in cecal contents of rabbits with mucoid enteropathy. Lab Anim Sci.1996; 46:179-186.
