JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
September 2018
D-M06

SIGNALMENT (AFIP #1431298):  6-month-old Appaloosa foal

HISTORY:  The foal was vaccinated 2 weeks prior to death for tetanus, Eastern equine encephalitis and Western equine encephalitis.  Clinical findings included blindness, incoordination, constipation, head pressing, icterus, AST=1800 (205-555 U/L), bilirubin=12 (0.1-1.9 mg/dl).

HISTOPATHOLOGIC DESCRIPTION:  Liver:  There is diffuse hepatic necrosis affecting the centrilobular and midzonal regions characterized by loss of hepatocytes, stromal collapse, distortion of the reticulin framework and replacement by eosinophilic cellular and karryohectic debris.  Remaining adjacent periportal hepatocytes are often individualized, degenerate with swollen, pale, vacuolated cytoplasm; necrotic, with shrunken hyper eosinophilic cytoplasm and pyknotic nuclei; or occasionally contain large, distinct, clear intracytoplasmic vacuoles (vacuolar change, lipid type).  Hepatic cords are disrupted and hepatocytes are individualized and separated by multifocal areas of hemorrhage, there are increased numbers of Kupffer cells which often contain phagocytosed erythrocytes and minimal amounts of globular brown pigment (hemosiderin or bile), and scattered lymphocytes and plasma cells.  Portal areas are mildly expanded by clear space (edema) and contain mildly increased amounts of fibrous connective tissue, few lymphocytes, plasma cells, macrophages, and rare neutrophils.

MORPHOLOGIC DIAGNOSIS:  Liver:  Hepatocellular necrosis and hepatocyte loss, submassive, diffuse, severe, with stromal collapse, hemorrhage, and biliary ductular reaction, Appaloosa, equine.

ETIOLOGIC DIAGNOSIS:  Unknown (flavivirus suspected)

CONDITION:  Equine serum hepatitis

SYNONYMS:  Theiler"s disease, idiopathic acute hepatic disease (IAHD), post-vaccinal hepatitis

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Chandriani S, Skewes-Cox P, et al. Identification of a previously undescribed divergent virus from the Flaviviridae family in an outbreak of equine serum hepatitis. Proc Natl Acad Sci USA. 2013; 110(15):E1407-15.
  2. Brown DL, Van Wettere AJ, and Cullen JM. Hepatobiliary System and Exocrine Pancreas. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:456.
  3. Cullen JM, Stalker MJ. Liver and Biliary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier Ltd; 2016:313-314.
  4. Divers TJ and Barton MH. Disorders of the Liver. In: Reed SM, Bayly WM, and Sellon DC, eds. Equine Internal Medicine. 4th ed. St. Louis, MO: Elsevier Ltd; 2018: 865-866.
  5. Divers TJ, Tennant BC, et al. New parvovirus associated with serum hepatitis in horses after inoculation of common biological product. Emerg Infect Dis. 2018; 24(2):303-310.


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