JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
September 2021
D-P11 (NP)

 

Signalment (JPC # 1644924): Golden pheasant (Chrysolophus pictus)

 

HISTORY: This pheasant was found dead in a zoo.

 

HISTOPATHOLOGIC DESCRIPTION: Cecum: Markedly expanding the submucosa and elevating the overlying mucosa are multifocal to coalescing nodules up to 2 mm in diameter composed of abundant spindle cells arranged in whorls and interlacing bundles admixed with macrophages, multinucleated giant cells, lymphocytes, and plasma cells. Nodules are often centered on adult or larval nematodes and/or one to multiple variably sized granulomas.  Adult nematodes are up to 500 um in diameter and have a thin (4-6 um thick), smooth, eosinophilic cuticle, lateral alae, polymyarian/coelomyarian musculature, lateral cords, a pseudocoelom, an intestinal tract lined by columnar uninucleate cells with a brush border, an ovary, and a uterus containing developing ova. Nodules often contain one or more variably sized granulomas with a central core of necrotic debris surrounded by a thin rim of epithelioid, hemosiderin-laden macrophages, multinucleated giant cells, and fewer fibroblasts, lymphocytes, and plasma cells. Diffusely the lamina propria is expanded by moderate numbers of lymphocytes, plasma cells, and fewer hemosiderin-laden macrophages often in aggregates, heterophils, and increased clear space (edema). The crypts are multifocally shallow and widely separated by the edematous lamina propria, and the superficial mucosa is multifocally eroded. Numerous small coccobacilli multifocally line the luminal epithelium.

 

MORPHOLOGIC DIAGNOSIS: Cecum: Typhlitis, granulomatous, multifocal, moderate, with atypical nodular mesenchymal proliferations, and adult and larval nematodes, etiology consistent with Heterakis isolonche, golden pheasant (Chrysolophus pictus), avian

 

ETIOLOGIC DIAGNOSIS: Cecal heterakiasis

 

CAUSE: Heterakis isolonche

 

GENERAL DISCUSSION:

• Order Ascarida, suborder Heterakina; primarily found in the cecum of birds
• Most heterakids are non-pathogenic, except for Heterakis isolonche
• isolonche most common in the pheasant; also reported in ducks, grouse, pheasants, prairie chickens, and quail
• Herterakiasis often called “verrucous typhlitis” due to the appearance of the cecal wall
• Recent report of large intestinal isolonche infection in a pheasant; nodular typhlocolitis progressed to neurofibromatous malignant mesenchymal neoplasia with pulmonary and hepatic metastases (Himmel, J Vet Diagn Invest. 2017)

 

LIFE CYCLE:

• Direct: Unembryonated eggs passed in feces > embryonate to reach infective stage in the environment in 12-14 days > bird ingests infective eggs directly or via transport host (annelid worm) > eggs hatch in crop, gizzard, or duodenum > larvae migrate to cecum and penetrate mucosa > adults develop with nodules > return to the cecal lumen to complete development

 

TYPICAL CLINICAL FINDINGS:

• May be asymptomatic
• Diarrhea and emaciation; high mortality with heavy infections

 

TYPICAL GROSS FINDINGS:

• Cecal wall thickened by multiple 1-2 mm, raised mucosal nodules (cobblestone appearance) that are white-gray, light pink, or dark brown; worms occasionally visible within nodules

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Nodules of proliferating fibrous tissue induced by larvae:
  • The nature of this reaction is controversial; it has been considered granulomatous, fibroplastic, or neoplastic
  • Nodules of spindle cells arranged in whorls and interlacing bundles have been described as “sarcomatous” or “pseudoneoplastic”
  • This nodular proliferation is not seen in quail and grouse
• Lymphoplasmacytic to granulomatous typhlitis
• Granulomas form in response to dead parasites
• Parasite morphology:
  • Thin, smooth cuticle, lateral cuticular alae, lateral cords, a pseudocoelom
  • Polymyarian/coelomyarian musculature
  • Intestinal tract: Cuboidal to columnar uninucleate cells with a brush border
  • Ovary and a uterus containing developing eggs
  • Differentiated from Heterakis gallinarum by size and appearance of spicules

 

ADDITIONAL DIAGNOSTIC TESTS:

• Fecal flotation may reveal heterakid eggs

 

COMPARATIVE PATHOLOGY:

• Heterakis beramporia: Similar lesion in chickens in Asia and the Pacific area
• gallinarum: No significant pathology, but carries Histomonas meleagridis, the etiologic agent of blackhead in gallinaceous birds; ring-necked pheasant is ideal host, followed by guinea fowl and chickens
• Heterakis bonasae: Infect ceca of ruffled grouse and Bobwhite quail; prevalence and worm burdens can be high
• Heterakis dispar: Infect ceca of ducks and geese but are relatively non-pathogenic
• Heterakis spumosa: Rodents

 

REFERENCES:

1. Fletcher OJ, Abdul-Aziz T. Alimentary System. In: Avian Histopathology, 4^th Ed. Madison, WI: American Association of Avian Pathologists. 2016: 276,344-345.
2. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissue. Washington DC: Armed Forces Institute of Pathology; 1999: 20.
3. Griner LA, Migaki G, Penner IR, McKee AE. Heterakidosis and nodular granulomas caused by Heterakis isolonche in the ceca of gallinaceous birds. Vet Pathol. 1977; 14: 582-590.
4. Himmel L, Cianciolo R. Nodular typhlocolitis, heterakiasis, and mesenchymal neoplasia in a ring-necked pheasant (Phasianus colchicus) with immunohistochemical characterization of visceral metastases. J Vet Diag Invest. 2017; 29(4): 561-565.
5. Menezes RC, Tortelly R, Gomes DC, Pinto RM. Nodular typhlitis associated with the nematodes Heterakis gallinarum and Heterakis isolonche in pheasants: Frequency and pathology with evidence of neoplasia. Mem Inst Oswaldo Cruz. 2003; 98: 1011-1016.
6. McDougald LR. Internal parasites. In: Swayne DE, ed. Diseases of Poultry, 14th ed. Hoboken, NJ: John Wiley & Sons, Inc.; 2020: 1164-1165.

 

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