Nodular Typhlitis Associated with Heterakis spp. in Golden Pheasants (Chrysolophus pictus): A Pathological and Immunohistochemical Investigation

This report details nodular typhlitis associated with Heterakis spp. in golden pheasants (Chrysolophus pictus) focusing on clinical and pathological findings. Necropsies found hemorrhagic ceca filled with multifocal white nodules. Histopathological analysis has shown necrotic foci, inflammatory infiltrations, and parasite fragments in the submucosa and tunica muscularis, and perivascular spindle-cell proliferation assumed a whirling pattern consistent with perivascular origin. Masson’s trichrome staining revealed only limited peripheral collagen, whereas the core nodules consisted of mesenchymal spindle cells with vimentin and α-smooth muscle actin (α-SMA) positivity, along with focal S-100 reactivity in some sections and uniform desmin negativity. While leiomyomas have been reported in Heterakis infections, the immunophenotypic profile—characterized by diffuse vimentin and SMA, occasional S-100 positivity, and absence of desmin—suggests a lesion with perivascular or undifferentiated mesenchymal features rather than a classical smooth muscle neoplasm or neurogenic tumor. Our observations thus expand the spectrum of pathological outcomes following chronic Heterakis infection in pheasants and underscore the value of immunohistochemistry in characterizing such spindle-cell lesions.