JPC SYSTEMIC PATHOLOGY

DIGESTIVE SYSTEM

August 2024

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. Necrotic foci 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, 1 x 5µm elongate 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 necrosis). Approximately 60% of colonic crypt lumina in the affected areas is 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, 1µm diameter, poorly staining, elongate bacilli. Submucosal lymphatic vessels are ectatic.  

 

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

 

ETIOLOGIC DIAGNOSIS: Clostridial colitis

 

CAUSE: Clostridium piliforme (formerly 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, and less commonly in dogs, and cats; can also affect other species

• Infection is more common in young, debilitated, or immunocompromised animals

• Classic triad of target organs: Liver, intestine, heart

• In foals, hepatic lesions are most consistent, and often the only gross lesions identified

• Clostridium piliforme is a pleomorphic, gram-negative (the only gram negative of the pathogenic clostridia), obligate intracellular, spore-forming rod 

• Can stain gram-positive (Oliveira et. al. J Vet Diagn Invest 2023)

 

PATHOGENESIS:

• Exact pathogenesis unknown; virulence factors/toxins have not been identified 
• Bacterium spread by fecal-oral route (ingestion of spores) -> spores or vegetative forms likely carried to small intestine where they infect mucosal epithelial cells and replicate within cells -> spread to liver (mechanism unknown) and replicate in hepatocytes and possibly Kupffer cells
• Liver damage is caused by acute coagulative necrosis of hepatocytes; intestinal mucosal epithelial cells similarly affected

 

TYPICAL CLINICAL FINDINGS:

• Peracute disease with sudden death in weanling and young animals (foals 7-42 days old), with or without diarrhea
• Foals may display depression, fever, anorexia, tachypnea, tachycardia, and jaundice; these can rapidly progress to shock, convulsions, and death 
• Elevated liver enzymes; leukopenia

 

TYPICAL GROSS FINDINGS:

• Icterus 
• Liver: Hepatomegaly with multiple random, 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: 

• Randomly distributed 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, highlighted by certain stains) in cytoplasm of hepatocytes at margins of necrotic foci or degenerate hepatocytes

• 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)

 

ADDITIONAL DIAGNOSTIC TESTS:

• Silver stains – Warthin-Starry, Steiner's, GMS
• Other histochemical stains: 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 E. 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 sp. (ileocolitis, crypt abscesses, small spiral bacteria)

 

COMPARATIVE PATHOLOGY:

• Reported in laboratory mice, rats, spinifex hopping mice, lagomorphs, rhesus monkeys, gerbils, guinea pigs, hamsters, cats, horses, canids, calves, birds, otters, whitetailed deer, ferrets, muskrats, monotremes and marsupials (including koalas, wombats, a dasyurid, brushtail and ringtail possums, and macropods), and red panda (suspected but not definitively diagnosed)
• In most species, potential lesions include hepatitis, ileitis, colitis, and myocarditis (plus or minus encephalitis) 
• Kittens: Colitis and hepatitis (not myocarditis); associated with immunocompromise due to maternal, environmental, infectious, and/or nutritional factors

• Cutaneous and neurologic infection in one kitten with concurrent feline panleukopenia virus infection (Oliveira et. al., J Vet Diagn Invest. 2023)

• One case of 2 dogs and a gray fox kit coinfected with canine distemper and C. piliforme (Jacobson et. al., Jour Vet Diagn Invest 2022)
• Mice: Low morbidity, high mortality; “classic triad” of GI, liver, heart affected

• DBA/2 mice susceptible, B6 mice resistant

• Rats: Megaloileitis (greatly dilated ileum), necrotizing ileitis, hepatic necrosis and hepatitis, linear myocardial necrosis, swollen mesenteric lymph nodes, pale foci of necrosis in the myocardium
• Rabbits: Miliary foci throughout the liver, linear myocardial necrosis, edema and necrotizing colitis
• Guinea pigs: Necrotizing ileitis and typhlitis, focal periportal hepatic necrosis and myocardial lesions not described; lesions in young animals may be confined to the intestinal tract
• Hamsters: Hepatic necrosis, enteritis and colitis, and 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

• Non-human primates:

• Rhesus monkey: incidental infection resulted in diarrhea in one reported case
• Cotton-top tamarins: infection in two young animals resulted in severe transmural necrotizing typhlocolitis with myocarditis and hepatitis, with bacteria observed in cecum, colon, liver, and heart; both animals had clinical histories of diarrhea and were found dead 3 months apart

 

REFERENCES:

1. Abee CR, Mansfield K, Tardif S, Morris T. Nonhuman Primates in Biomedical Research: Volume 2: Diseases. 2nd ed. San Diego, CA: Elsevier; 2012:123.
2. 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.
3. 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. 
4. Delaney MA, Treuting PM, Rothenburger JL. Lagomorpha. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:493. 
5. Delaney MA, Treuting PM, Rothenburger JL. Rodentia. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:510. 
6. Fingerhood S, Mendonça FS, Uzal FA, et. al. Tyzzer disease in 19 preweaned orphaned kittens. J Vet Diagn Invest. 2023;35(2):212-216.
7. García JA, Navarro MA, Fresneda K, Uzal FA. Clostridium piliforme infection (Tyzzer disease) in horses: retrospective study of 25 cases and literature review. J Vet Diagn Invest. 2021: 1-8
8. Higgins D, Rose K, Spratt D. Monotremes and Marsupials. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambrige, MA, Elseveir, 2018: 468.
9. Howerth EW, Nemeth NM, Ryser-Degiorgis MP. Cervidae. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:164. 
10. Jacobson SA, Ferro PJ, Navarro MA, et. al. Clostridium piliforme and canine distemper virus coinfection in 2 domestic dog littermates and a gray fox kit. J Vet Diagn Invest. 2022;34(5):894-897. 
11. Keel MK, Terio KA, McAloose D. Canidae, Ursidae, and Ailuridae. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:244. 
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13. Oliveira ES, Queiros CRR, Santos DO, et. al. Neurologic and cutaneous infection by Clostridium piliforme in a kitten with systemic Tyzzer disease. J Vet Diagn Invest. 2023;35(3):322-326.
14. Spagnoli ST, Gelberg HB. Alimentary System and the Peritoneum, Omentum, Mesentery, and Peritoneal Cavity. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:452-453. 
15. Stanton JB, Zachary JF. Mechanisms of Microbial Infections. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:209-210. 
16. Uzal FA, Arroyo LG, Navarro MA, et. al. Bacterial and viral enterocolitis in horses: a review. J Vet Diagn Invest. 2022;34(3)354-375.
17. 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.
18. Van Wettere AJ, Brown DL. Hepatobiliary System and Exocrine. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:515-516. 

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