JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
December 2018
D-V29 (NP)

Signalment (JPC #2469833):  Merino lamb

HISTORY:  This animal was from a flock where a few abortions and neonatal deaths had occurred.  There were no floodwater pools on the farm, but there were increased numbers of mosquitoes when compared to the previous 4-5 years.

HISTOPATHOLOGIC DESCRIPTION:  Liver:  Diffusely there is massive lytic necrosis of all regions of the hepatic lobule characterized by dissociation of hepatic cord architecture with loss of hepatocytes and replacement by small amounts of cellular and karyorrhectic debris, a moderate number of viable and degenerate neutrophils often in small aggregates, fibrin, and hemorrhage. Remaining hepatocytes are either degenerate, characterized by swollen, pale, vacuolated cytoplasm with faded nuclei (karyolysis) or individualized and shrunken with hypereosinophilic cytoplasm and pyknotic or karyorrhectic nuclei (necrotic). Few degenerate and necrotic hepatocytes contain 5 to 10 um eosinophilic, intranuclear viral inclusion bodies and/or variably sized, typically round eosinophilic intracytoplasmic bodies (cytosegresomes).  Expanding periportal connective tissue are low numbers of macrophages, lymphocytes, and plasma cells. 

MORPHOLOGIC DIAGNOSIS:  Liver:  Necrosis, massive, subacute, diffuse, moderate, with hepatocellular eosinophilic intranuclear viral inclusion bodies and eosinophilic intracytoplasmic inclusion bodies, Merino sheep, ovine.

ETIOLOGIC DIAGNOSIS:  Flaviviral hepatitis

CAUSE:  Wesselsbron virus (flavivirus)

CONDITION:  Wesselsbron’s disease

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL MICROSCOPIC FINDINGS:

DIAGNOSIS:

DIFFERENTIAL DIAGNOSIS:

Hepatic necrosis

Abortions:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Brown DL, Van Wettere AJ, 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: 457-458.
  2. Systemic and multi-organ diseases. In: Constable PD, Hinchcliff KW, Done SH, Grunberg W, eds. Veterinary Medicine, A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs, and Goats. 11th ed. St. Louis, MO: Elsevier; 2017:2084-2086.
  3. Uzal FA, Plattner BL, Hostetter JM. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA: Elsevier; 2016:312.
  4. Zachary JF. Mechanisms of microbial infections. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:206-207.


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