Characteristic Gross, Histopathological and Electron Microscopy Features of Zygomycosis (Rhizopus spp.) in an Adult Breeder Bird

Zygomycosis due to Rhizopus spp. was diagnosed in a 40 week old male adult breeder bird out of three birds submitted to the department for necropsy. Grossly raised hard, firm nodule of 7 x 5 x 3 cm diameter (length x width x height) was observed on the left side of breast muscle. Nodules of varied size were also observed on the surface of lung, air sac, and below the lung attached to rib cage. Proventriculus with irregular size raised nodule on serosal surface and erosion on mucosal surface was observed. Histopathological examination of muscle, lung and PV showed central core of caseous eosinophilic cellular masses admixed with appreciable number of degenerating heterophils and collar of lymphocytes, macrophages and foreign body giant cells, surrounded by fibrous connective tissue. The culture growth on Sabouraud’s dextrose agar was brown coloured colonies which alter staining with lacto-phenol cotton blue stain revealed number of roots like filaments with non-septate hyphae opposite to the base of the aerial sporangiophores. The TEM of tissue specimen revealed numerous non-septate hyphae in tissue samples. Hyphae appeared to be empty, non-branching with variation in shape, size and diameter. SEM examination of the culture samples revealed long, unbranched sporangiophore along with terminally attached sporangium with average size of 3.87 µm. In the present study, we have confirmed unequivocally the occurrence of Rhizopus in an adult bird. It is rare case occurred secondary to the stress of Marek’s disease in a flock.