Nocardia cyriacigeorgica in a Mallard Duck

Nocardia spp. are opportunistic pathogens of humans, domestic animals, and wildlife that can cause high levels of morbidity and mortality. Reported cases of nocardiosis in Aves are rare. We diagnosed nocardial airsacculitis in a free-ranging mallard duck (Anas platyrhynchos) from Arizona, USA. Histopathology showed multiple granulomas expanding the air sac with intralesional filamentous bacteria that were Grocott's methenamine silver positive, Fite-Faraco and Ziehl-Neelsen acid-fast, positive with the Periodic acid-Schiff reaction, and variably Gram positive. The organism was isolated in culture and identified as Nocardia cyriacigeorgica based on sequencing of a 463 bp portion of the 16S rRNA gene. Nocardiosis should be considered as a differential diagnosis for airsacculitis in Aves.