Microsporidiosis in a flock of tricolor parrot finches (Erythrura tricolor).

The lesions caused by a microsporidian infection in a flock of tricolor parrot finches (Erythrura tricolor) are described. Affected birds had a widespread nodular to diffuse granulomatous inflammation of the serosal surfaces of the gastrointestinal tract, peritoneum, perirenal airsacs and connective tissue, bone marrow, dura, and conjunctiva. This was composed predominantly of foamy macrophages containing numerous intracytoplasmic microsporidia measuring 1 to 2 microm. Ultrastructural features consistent with microsporidia were the presence of a coiled polar filament and an electrode-dense outer surface and thick electron-lucent capsule. Differential diagnoses included infection with intracellular organisms, including coccidian and other apicomplexan parasites, such as lsospora, Eimeria, and blood parasites; Chlamydophilosis; disseminated mycobacteriosis; and other bacterial and fungal species.