JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
September 2018
D-F06

SIGNALMENT (JPC #4111382-00): 2-year-old male common canary (Serinus canaria)

HISTORY:  These canaries were acquired from a pet store, and subsequently used in an avian malaria study.  Some birds tested positive for Cryptosporidium galli but failed to respond to therapy.  The birds were euthanized at the end of the study.  No gross lesions were noted.

HISTOPATHOLOGIC DESCRIPTION: Isthmus, ventriculus, proventriculus:  Infiltrating approximately 60% of the length of the proventriculus and extending through the isthmus to ventriculus are 2 x 20 um, basophilic, rod-shaped yeast that are stacked end-to-end in a linear fashion and line the mucosa or rarely expand the lumen of superficial proventricular glands.  Superficial proventricular mucosa has increased numbers of goblet cells. Scattered throughout the proventriculus, the glandular epithelial cells are occasionally swollen and vacuolated (degenerate) or rarely shrunken with hypereosinphilic cytoplasm and a pyknotic nucleus (necrosis).  Multifocally, glands are mildly ectatic with luminal proteinaceous material.  Within the lamina propria of the ventriculus and proventriculus, there are variable sized aggregates of lymphocytes and histiocytes and minimal fibrosis separating some glands.  The koilin layer is diffusely attenuated with disorganization near the isthmus and a focal area of loss with replacement by aggregates of yeast.

Liver: Affecting less than 20% of the liver are variably sized nodules of lymphocytes and macrophages.  Multifocally, there are random foci of Kupffer cells that contain a variably sized vacuole (lipogranulomas). (likely unrelated to the gastric yeast)

MORPHOLOGIC DIAGNOSIS:

  1. Isthmus, ventriculus, proventriculus: Proventriculitis and ventriculitis, lymphocytic, histiocytic, multifocal, moderate with koilin attenuation, goblet cell hyperplasia, and numerous intralesional yeast, common canary (Serinus canaria), avian.
  2. Liver: Hepatitis, lymphohistiocytic, multifocal, chronic, moderate with lipogranulomas. 

ETIOLOGIC DIAGNOSIS: Proventricular macrorhabdiosis

CAUSE:  Macrorhabdus ornithogaster

SYNONYMS:  avian gastric yeast, megabacteria

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTICS:

DIFFERENTIAL DIAGNOSIS:

References:

  1. Boulianne M, et al. Avian Disease Manual.  7th  Jacksonville, FL: AAAP;2013:30-34.
  2. Jordan FTW, Hampson DJ. Some other bacterial diseases. In: Pattison M, McMullin P, Bradbury J, Alexander D. eds. Poultry Diseases. Sixth Edition. Elsevier. Ithaca, New York. 2007: 249.
  3. Phalen DN. Update on the diagnosis and management of Macrorhabdus ornithogaster (formerly megabacteria) in avian patients. Vet Clin North Am Exot Anim Pract. 2014 May;17(2):203-210.
  4. Schmidt RE, Reavill DR, Phalen DN. In: Schmidt RE, Reavill DR, Phalen DN. eds. Pathology of Pet and Aviary Birds, Second Edition. Iowa State Press.. Ames, Iowa. 2015: 65, 70, 81.
  5. Smith JA. Passeriformes (songbirds, perching birds). In: Miller RE, Fowler M, eds. Fowler's Zoo and Wild Animal Medicine. Vol 8. St. Louis, MO: Elsevier; 2015:243.
  6. Snyder JM, Treuting PM. Pathology in practice. Adenocarcinoma of the proventriculus with liver metastasis and marked, diffuse chronic-active proventriculitis and ventriculitis with moderate M. ornithogaster infection in a budgerigar. J Am Vet Med Assoc. 2014; 15;244(6):667-669.
  7. Tomaszewski EK, Logan KS, Snowden KF, et al. 2003. Phylogenetic analysis identifies the “megabacterium” of birds as a novel anamorphic ascomycetous yeast, Macrorhabdus ornithogaster nov., sp. nov. Int J Syst Evol Microbiol. 2003; 53(4):1201–1205.


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