JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
August 2021
D-B06

Slide A: 

SIGNALMENT (JPC #1901209):  3-week-old foal

 

HISTORY:  Found dead.

 

HISTOPATHOLOGIC DESCRIPTION:  Liver:  Multifocally and randomly affecting approximately 70% of the hepatic parenchyma, there are numerous, coalescing, up to 2 mm diameter foci of lytic necrosis characterized by replacement of parenchyma with eosinophilic cellular and karyorrhectic debris, infiltrated by often necrotic neutrophils, and admixed with fibrin, edema, hemorrhage, and few individualized hepatocytes. Lytic foci of necrosis are rimmed by large numbers of viable and necrotic neutrophils and fewer macrophages and lymphocytes.  Hepatocytes rimming necrotic foci are often either swollen with pale, vacuolated cytoplasm (degenerate), shrunken and hypereosinophilic with pyknotic nuclei (necrotic), or have retention of cellular architecture and loss of differential staining (coagulative necrosis).  Peripheral to these hepatocytes, less affected hepatocytes often contain numerous intracytoplasmic, stacked, pale, basophilic, elongate, 1x 5um bacilli.  Portal areas and the subcapsular space are expanded up to three times normal by ectatic lymphatic vessels (edema), hemorrhage, fibrin, and low numbers of lymphocytes, plasma cells, macrophages, and rare neutrophils , and portal areas contain increased bile duct profiles (biliary ductular reaction).

 

Slide B:  Liver (Warthin-Starry, pH 4.0): Hepatocytes at the periphery of necrotic areas contain many intracytoplasmic, argyrophilic, elongate bacilli. Bacilli are arranged in parallel and perpendicular sheaves and bundles as well as individually.  Occasionally bacilli are free within necrotic debris.

 

MORPHOLOGIC DIAGNOSIS:  Liver:  Hepatitis, necrosuppurative, random, acute, multifocal to coalescing, severe, with intracellular argyrophilic bacilli, breed not specified, equine.

 

ETIOLOGIC DIAGNOSIS:  Clostridial hepatitis

 

SLIDE C:

SIGNALMENT (JPC #4048999):  1-month-old domestic short hair cat

 

HISTORY: This patient had upper respiratory signs, diarrhea, and dehydration and eventually died despite care. Three kittens within this litter died.

 

HISTOPATHOLOGIC DESCRIPTION: Colon: The mucosal layer is segmentally expanded up to two times normal by infiltration of the lamina propria by moderate numbers of lymphocytes, plasma cells, macrophages, fewer neutrophils, fibrin, edema, and dilated lymphatic vessels; this inflammation occasionally extends into the submucosa and inner circular layer of the muscularis externa. Mucosa within the affected area exhibits marked loss of goblet cells, increased numbers of mitotic figures, and rare enterocytes are shrunken with hypereosinophilic cytoplasm and angular, pyknotic nuclei (single cell death).  Approximately 60% of colonic crypt lumina in the affected areas are expanded by previously described inflammatory cells, sloughed mucosal epithelial cells, necrotic debris, and basophilic mucinous material (crypt abscesses); these crypts are lined by either cuboidal or attenuated epithelium. Occasionally the cytoplasm of enterocytes, including occasional sloughed enterocytes within crypt abscesses, contains bundles of crisscrossing, 1um diameter, poorly staining, elongate bacilli. Submucosal lymphatic vessels are ectactic.    

 

MORPHOLOGIC DIAGNOSIS:  Colon: Colitis, lymphoplasmacytic and histiocytic, segmental, chronic, moderate, with crypt abscesses and intra-enterocyte bacilli.

 

ETIOLOGIC DIAGNOSIS:  Clostridial colitis

 

CAUSE:  Clostridium piliforme (previously Bacillus piliformis)

 

SYNONYMS:  Tyzzer's disease

 

GENERAL DISCUSSION:

• Acute, fatal, enterohepatic disease of young or immunocompromised animals of many species, primarily recognized in laboratory rodents, rabbits, foals, dogs, and cats; can also affect other species
  • Bacterial strain differences may occur between hosts; most isolates are host specific but some appear to be cross-infective
  • Infection is more common in weanling, debilitated, or immunocompromised animals; stress associated with overcrowding, shipping, breeding, or high temperatures is thought to predispose animals to infection
  • In cats, associated with feline infectious peritonitis virus; feline leukemia virus infection in kittens; one report in kittens with feline panleukopenia virus; one case report concurrent with feline rhinotracheitis
• Classic triad of target tissues: Liver, intestine, heart
• Clostridium piliforme is a pleomorphic, gram-negative (the only gram negative of the pathogenic clostridia), obligate intracellular, spore-forming rod
• Vegetative form:
  • Bacteria look like “bundles” or “sheaves” within cells
  • Active stage responsible for disease
  • Extremely labile outside the host
• Spore form:
  • Not easily seen in tissue
  • Responsible for transmission by fecal-oral route
  • Can survive up to a year at room temperature (e.g. in contaminated bedding)

 

PATHOGENESIS:

• Exact mechanism of spread from ingestion to the liver is unclear
• Transmission of Clostridium piliforme is fecal-oral > carried by normal peristaltic activities through the oral pharynx, esophagus, and stomach to the small intestine (ileum) > gain access to the intestinal mucosal epithelium > bacteria spread via portal circulation to liver > colonization of hepatic parenchyma > multifocal necrosis
• In rodents, experimental transplacental transmission has been reported

 

TYPICAL CLINICAL FINDINGS:

• Peracute disease with sudden death in weanling and young animals (foals 7-42 days old), with or without diarrhea
• Elevated liver enzymes; leukopenia

 

TYPICAL GROSS FINDINGS:

• Icterus,
• Liver: Hepatic enlargement with multiple pinpoint to miliary gray foci
• Intestine: Necrotizing enterocolitis with marked congestion and edema
• Heart: Occasional white linear bands in myocardium
• Lymph nodes: Hemorrhagic and edematous lymph nodes

 

TYPICAL MICROSCOPIC FINDINGS:

• Liver:
  • Multifocal to coalescing irregular areas of hepatic necrosis, often surrounded by hemorrhage, macrophages, and neutrophils
  • Parallel or crisscrossed bundles or stacks of bacilli (faintly staining on H&E) in cytoplasm of hepatocytes at margins of necrotic foci
• Intestine: Enterocolitis, often necrotizing, described in foals and other species
  • Bundles of bacteria within enterocytes
  • Crypt abscesses
• Heart: Foci of myocardial necrosis
• CNS: microabscessation with bacteria within neurons (birds and gerbils)

 

ULTRASTRUCTURAL FINDINGS:

• Bacilli in cytoplasm of cells
• Vegetative forms have numerous peritrichous flagella (flagella distributed over the entire cell surface).

 

ADDITIONAL DIAGNOSTIC TESTS:

• Silver stains - Warthin Starry (4.0), Steiner's, GMS
• Other histochemical stains: Also demonstrated with Methylene blue, Giemsa
• Immunohistochemistry
• PCR
• Culture: Will not grow on cell free media

 

DIFFERENTIAL DIAGNOSIS:

Random necrotizing hepatitis in foals:

• Equine herpesvirus I: Hepatic necrosis, concurrent interstitial pneumonia, intranuclear inclusion bodies in hepatocytes
• Salmonella sp. or coli septicemia: Watery, foul smelling diarrhea, joint lesions, pneumonia and/or meningitis (with Salmonella sp); differentiate by bacterial morphology and stains
• Sleepy foal disease (Actinobacillus equuli): Multifocal hepatitis, severe enteritis, embolic nephritis; differentiate by bacterial morphology and stains

Colitis in kittens:

• Tritrichomonas foetus: large bowel diarrhea in cats < 1 year of age; refractory to treatment
• Mycotic colitis: Candida, Zygomycetes, Aspergillus; hemorrhagic and ulcerative colitis with microthrombosis; usually secondary to feline panleukopenia virus
• FIV, FeLV, Giardia
• Entamoeba histolytica: necrotic colitis with amoeba
• Bacterial colitis: Salmonella Typhimurium (transmural ulcerative colitis), Anaerobiospirillum (ileocolitis, crypt abscesses, small spiral bacteria)

 

COMPARATIVE PATHOLOGY:

• Reported in laboratory mice, rats, lagomorphs, rhesus monkeys, gerbils, guinea pigs, hamsters, cats, horses, canids, calves, birds, otters, whitetail deer, ferrets, muskrats, monotremes and marsupials.
• In most species lesions are similar to include hepatitis, ileitis, colitis, myocarditis plus or minus encephalitis.
• Rats: Megaloileitis (greatly dilated ileum), necrotizing ileitis, hepatic necrosis and hepatitis, linear myocardial necrosis
• Rabbits: Miliary foci throughout the liver, linear myocardial necrosis, edema and necrotizing mucosal colitis
• Guinea pigs: Necrotizing ileitis and typhlitis, focal periportal hepatic necrosis and NO myocardial lesions
• Hamsters: Hepatic necrosis, enteritis, granulomatous myocarditis
• Gerbils:
  • Mongolian gerbil especially susceptible; used as a sentinel in research facilities
  • Pinpoint foci of necrosis in liver, necrotizing ileitis and typhlitis, focal myocardial necrosis, encephalitis
• Avian: encephalitis caused by Clostridium piliforme

 

REFERENCES:

1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, Iowa: Blackwell Publishing; 2016: 53-54,137-138, 181-182, 201-203, 225, 275-276.
2. Cullin JM, Stalker MJ. Liver and biliary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. 6th ed. Vol 2. Philadephia, PA: Elseveier; 2016:317-318.
3. García JA, Navarro MA, Fresneda K, Uzal FA. Clostridium piliformeinfection (Tyzzer disease) in horses: retrospective study of 25 cases and literature review. J Vet Diagn Invest. 2021: 1-8
4. Higgins D, Rose K, Spratt D. Monotremes and Marsupials. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wild Life and Zoo Animals. Cambrige, MA, Elseveir, 2018: 468.
5. Jenkins JR, Oglesbee BL. Gastrointestinal diseases. In: Carpenter JW, Quesenberry KE, eds. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. St Louis, MO: Elsevier Saunders; 2012:199-200.
6. Mete A, et al. Tyzzer’s disease in free-ranging passerine birds in California, USA. J Wildl Dis2017;53:938–941.
7. Navarro MA, Uzal FA. Pathobiology and diagnosis of clostridial hepatitis in animals. J Vet Diagn Invest. 2020;32(2):192-202
8. Neto RT, Uzal FA, Hodzic E, Persiani M, Jolissaint S, et al. Coinfection with Clostridium piliforme and Felid herpesvirus 1 in a kitten. J Vet Diagn Invest. 2015; 27(4):547-51.
9. Pearson EG. Tyzzer’s Disease in Foals. In: Smith B, ed. Large Animal Internal Medicine. 4th ed. St. Louis, Missouri: Mosby; 2009:902.
10. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. 6th ed. Vol 2. Philadephia, PA: Elseveier; 2016 : 98-99, 113-114, 117, 183-194, 199.
11. Zachary JF. Mechanisms of microbial infections. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:166-167.

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