Signalment:  

Young male, golden pheasant (Chrysolophus pictus).Second young male that died 2 weeks after purchase.

Gross Description:  

The caeca were dilated with multiple small areas of necrosis of the mucosa and thickening of the mucosa.

Histopathologic Description:

Cecum: The submucosa and the tunica muscularis contain multiple ascarid larvae. They have pronounced cuticles with lateral alae. The coelomyarian muscles are cylinder-shaped and divided in two sections by large lateral chords. Some cross sections contain eosinophilic glands associated with the lateral chords. The intestine consists of large uninucleated columnar cells. Some thick-shelled eggs are present in the lamina propria. Around some parasites, there is a granulomatous inflammation present with necrosis, multinucleated giant cells and heterophils.

Around most of the larvae there is a large unencapsulated, well-demarcated, infiltrative, multilobular, densely cellular mass. The cells are closely packed and growing in bundles and whorls separated by fine fibrovascular stroma. The cells are spindled and large, with a moderate amount of fibrillar eosinophilic cytoplasm which is sometimes vacuolated, and have indistinct borders and central oval nuclei with vesicular chromatin and a prominent nucleolus. The cells and nuclei show moderate variation. Mitoses are 0-1 per HPF.

The epithelium and the crypts show necrosis with infiltration of heterophils. The lamina propria shows a diffuse mixed infiltration of inflammation cells.

Morphologic Diagnosis:  

1. Caecum, nodular granulomatous typhlitis and presence of multiple Heterakis larvae.
2. Caecum, leiomyoma.

Lab Results:  

Immunohistochemical staining for smooth muscle actin was positive.

Condition:  

Heterakis gallinarum; multiple leiomyomas

Contributor Comment:  

Heterakis gallinarum is a widespread parasite with a prevalence up to 90%.(1,2) The parasite has a direct life cycle and can cause tissue damage in the caeca of infective birds. The infective eggs can host Histomonas meleagridis which causes blackhead disease.

The main lesion in the intestinal wall is the presence of granulomatous nodules in the caecal wall, mostly in the submucosa. Sometimes, the lesions are accompanied by neoplastic nodules in the submucosa or the muscular tunic. The neoplastic nodules can be of variable origin: fibrous hyperplastic tissue, fibrohistiocytic nature and leiomyomas have been described. In this case the nodule was a leiomyoma based on immunohistochemical staining , which is believed to be induced by immature specimens of Heterakis spp.2

JPC Diagnosis:  

Cecum: Typhlitis, transmural, granulomatous, multifocally extensive, marked, with atypical nodular mesenchymal proliferation, and nematode adults, larvae and eggs, etiology consistent with Heterakis species.

Conference Comment:  

Conference participants were equally divided between assigning a morphologic diagnosis of leiomyoma versus nodular mesenchymal proliferation. All participants agreed with the interpretation of a benign nodular spindle cell proliferation with smooth muscle features in association with the nematode, but many did not interpret the proliferative lesion as neoplastic, thus the histologic diagnosis of atypical mesenchymal nodular proliferation. A Massons trichrome stain performed at the AFIP demonstrated the presence of abundant collagen with light staining for muscle within the lesion in the mesenchymal nodules. Additionally, the proliferative spindle cells were negative for smooth muscle by tissue immunohistochemistry in our laboratory. We interpret these findings as more suggestive of a reactive myofibroblastic proliferation vice smooth muscle neoplasia in the case of this pheasant.

Most conference participants favored Heterakis isolonche as the etiology, though all included H. gallinarum on the differential diagnosis. In general, H. gallinarum more commonly parasitizes domestic poultry and, other than carrying Histomonas meleagridis, it is not usually associated with pathologic changes. Heterakis isolonche is a pathogenic parasite of game birds, especially pheasants, and causes typhlitis, nodular proliferations and diarrhea.(3) A presumptive diagnosis of H. isolonche can be made during necropsy by the presence of the parasite within cecal nodules. Definitive differentiation between the two species requires histologic examination and is based on the presence of spicules of either unequal or equal length in H. gallinarum and H. isolonche, respectively.(3)

References:

1. Draycott RAH, Parish DMB, Woodburn MIA, Carroll JP. Spring survey of the parasite Heterakis gallinarum in wild-living pheasants in Britain. Vet Rec. 2000;147:245-246.

2. 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(8):1011-1016.

3. Urquhart GM, Armour J, Duncan JL, Dunn AM, Jennings FW. Veterinary helminthology. In: Veterinary Parasitology. 2nd ed. Cambridge, MA: Blackwell Science, Inc.; 1996:76-77.

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