JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
October 2018
D-V04

Signalment (JPC# 2019022):  BALB/c nu/nu mouse

HISTORY: D-V04A:  This mouse died after inoculation with an infectious agent.

HISTOPATHOLOGIC DESCRIPTION:  Liver:  Multifocally and randomly affecting approximately 60% of the liver are areas of hepatocellular degeneration, necrosis, and loss. These foci of necrosis are characterized by loss of hepatic tissue and cellular architecture and replacement by eosinophilic cellular and karyorrhectic debris (lytic necrosis) and loss of differential staining and retention of hepatic architecture (coagulative necrosis) admixed with viable and degenerate neutrophils, macrophages, and lymphocytes with variable amounts of hemorrhage, fibrin, and edema.  Multinucleated viral syncytial cells that contain up to 30 small, pyknotic nuclei are frequently present within the necrotic foci, which may represent endothelial and/or parenchymal syncytia.    In the adjacent parenchyma, hepatocytes are swollen and often vacuolated (degeneration) and compress the adjacent sinusoids.  There is multifocal indentation of the hepatic capsule overlying areas of stromal collapse, which has occurred secondary to necrosis and hepatocyte loss.  Rarelyviral syncytial cells are present within the tunica intima of hepatic vessels.  Periportal areas are expanded by edema and there are dilated lymphatics.

MORPHOLOGIC DIAGNOSIS:  Liver:  Hepatitis, necrotizing, acute, random, multifocal, marked, with numerous viral syncytia consistent with Mouse Hepatitis Virus, BALB/c nu/nu mouse, rodent.

Signalment (JPC# 2316944):  Mouse

HISTORY:  D-V04B:  Tissue from a quality control mouse.

HISTOPATHOLOGIC DESCRIPTION:

  1. Duodenum:  There is multifocal to coalescing blunting, fusion, and loss of villar tips, which often contain large viral syncytial cells, up to 150um diameter, with pale flocculant cytoplasm and up to 20 nuclei.
  2. Lymph node: Multifocally within the paracortex there are coalescing areas of lytic necrosis with lymphocytolysis, loss of normal architecture and replacement by necrotic debris.
  3. Stomach; pancreas: No significant lesions.

MORPHOLOGIC DIAGNOSIS:  

  1. Duodenum:  Villar blunting, fusion and loss, diffuse, mild, with numerous epithelial syncytia consistent with Mouse Hepatitis Virus, mouse strain unspecified, rodent.
  2. Lymph node: Lymphocytolysis, multifocal. 

ETIOLOGIC DIAGNOSIS:  Coronaviral hepatitis

CAUSE:  Mouse Hepatitis Virus (MHV - murine coronavirus)

SYNONYM:  Lethal Intestinal Virus of Infant Mice (LIVIM)

GENERAL DISCUSSION:

  1. Polytropic (eg. MHV-JHM, MHV-A59, MHV-S, MHV-3) initially replicates in nasal mucosa & disseminates to other organs
    • Immunocompromised animals : Systemic disease; acute necrosis with syncytia in liver, splenic red & white pulp, GALT, thymus and bone marrow
    • Neonatal mice: Vascular-oriented necrotizing encephalitis with spongiosis and demyelination in brain stem
    • C3H mouse: Semi-susceptible
    • BALB/c & DBA/2 mice: Susceptible
    • SJL mouse: Resistant
  1. Enterotropic (MHV-S/CDC, MHV-Y, MHVR1, MHV-D) infects intestinal mucosa of terminal ileum, cecum, ascending colon & rarely disseminates
    • Neonatal mice: Severe necrotizing enterocolitis; high mortality
    • Adult mice: Minimal lesions - enterocyte syncytia in the cecum and ascending colon
    • Immunodeficient adult mice: Minimal hyperplasia in intestinal mucosa
    • Adult nude mice: Mild intestinal lesions with minimal mucosal hyperplasia; can develop a chronic hyperplastic typhlocolitis and mesenteric lymphadenopathy
    • SJL mouse: Susceptible to enterotropic

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

ULTRASTRUCTURAL FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents & Rabbits. 4th ed. Ames, IA: John Wiley & Sons, Inc.; 2016:27-31.
  2. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:146-151, 529, 541-542.


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