JPC SYSTEMIC PATHOLOGY
HEMOLYMPHATIC SYSTEM
April 2018
H-V03

Signalment (JPC #1780888):  Blue-gold macaw

HISTORY:  Tissue from a macaw that died suddenly

HISTOPATHOLOGIC DESCRIPTION:  Thymus:  Diffusely there is depletion of cortical lymphocytes and multifocal areas of necrosis primarily within the medulla. Areas of necrosis are characterized by moderate amounts of eosinophilic necrotic debris admixed with fibrin, low numbers of remaining lymphocytes and thymic epithelial cells. There are many large viral syncytial cells up to 70 um in diameter, containing up to 20 nuclei.  Often within the nuclei of syncytial cells and epithelial cells are 10 um brightly eosinophilic viral inclusion bodies that fill the nucleus and marginate chromatin.

Spleen:  There is  diffuse depletion of white pulp with a paucity of lymphocytes.  Multifocally, there are small areas of necrosis within both the red and white pulp.  Histiocytes often contain phagocytosed nuclear or cellular debris or erythrocytes (erythrophagocytosis).

Liver:  Diffusely there is loss of hepatic cord architecture with marked hepatic degeneration (vacuolation, cellular swelling), necrosis (hypereosinophilic shrunken cytoplasm to eosinophilic cellular debris with pyknosis and karyolysis), and abundant dissociation or individualization of hepatocytes (degeneration with loss of adhesion).  Degenerate hepatocytes (adjacent to areas of necrosis) contain a 10 um intranuclear eosinophilic to amphophilic viral inclusion which fills the nucleus and marginates chromatin.  There are increased numbers of lymphocytes and Kuppfer cells throughout the hepatic parenchyma.

MORPHOLOGIC DIAGNOSIS: 

  1. Thymus:  Lymphoid depletion and necrosis, acute, multifocal to coalescing, marked with viral syncytial cells, and thymocytes with eosinophilic intranuclear viral inclusion bodies, blue-gold macaw, avian.
  2. Spleen: White pulp depletion, acute, diffuse, marked with multifocal necrosis.
  3. Liver: Degeneration and necrosis, massive, acute, diffuse, severe, with hepatocellular eosinophilic intranuclear viral inclusion bodies. 

ETIOLOGIC DIAGNOSIS:  Herpesviral thymic, splenic, and hepatic necrosis.

CAUSE:  Psittacid herpesvirus 1

CONDITION:  Pacheco’s disease

SYNONYMS: Herpesvirus of psittacine birds; Amazon parrot herpesvirus; Pacheco"s parrot disease

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURAL FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

Alphaherpesviruses

REFERENCES:

  1. Abdul-Aziz T, Fletcher OJ. Hepatobiliary system. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. Jacksonville, FL: AAAP; 2016:389-390.
  2. Cheville NF. Ultrastructural Pathology: The Comparative Cellular Basis of Disease. 2nd ed. Ames, Iowa: Blackwell Publishing; 2009:327-335.
  3. Gabor M, Gabor LJ, Peacock L, Srivastava M, Rosenwax A, Phalen D. Psittacid herpesvirus 3 infection in the eclectus parrot (Eclectus roratus) in Australia. Vet Pathol. 2013;50(6):1053-1057.
  4. Gailbreath KL, Oaks JL. Herpesviral inclusion body disease in owls and falcons is caused by the pigeon herpesvirus (columbid herpesvirus 1). J Wildl Dis. 44: 427-33, 2008.
  5. MacLachlan NJ, Dubovi EJ, eds. Fenner’s Veterinary Virology. 4th ed. London, UK; 2011:179-201.
  6. Randall CJ, Reece RL. Color Atlas of Avian Histopathology. New York, NY: Mosby-Wolfe; 1996:93.
  7. Ritchie BW, Harrison GJ, Harrison LR. Avian Medicine: Principles and Application. Lake Worth, FL: Wingers Publishing, Inc; 1994:875, 878-879.
  8. Schmidt RE, Reavilll DR, Phalen DN. Pathology of Pet and Aviary Birds. Ames, IA:Iowa State Press; 2015:23-30, 78, 79, 87, 96-98, 130, 181, 183, 247, 283.


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