Background and Aim: Aspergillus fumigatus is a ubiquitous pathogen causing aspergillosis in poultry. This research aimed to evaluate the clinical and pathological features of aspergillosis infection in broilers.

Materials and Methods: A. fumigatus infection was induced experimentally by intra-air sac inoculation of a 1.7×10⁸ spore suspension into broilers. Infected and non-infected birds were closely observed for the development of clinical signs of infection twice daily. Pathological samples were collected 5, 14, and 30 days post-infection (dpi) and examined by hematoxylin-eosin staining.

Results: A total of 160 birds were included in this study. Clinical signs emerged at 3 dpi and became consistent at 5 dpi. A considerable decrease in severity and number of birds showing infection symptoms followed. The clinical signs of aspergillosis included anorexia (n=40; 50%), lethargy (n=32; 40%), dyspnea (n=38; 48%), and gasping (n=29; 36%). Macroscopic changes in the air sacs at 3 dpi included the development of minor lesions showing cloudiness, slight membrane thickening, and local exudates. Histopathological examination of the air sacs collected at 3 dpi indicated local inflammation surrounded by hyphae and spores. At 5 dpi, infected birds developed nodules, necrosis, and parenchymal consolidation of the lungs. Pulmonary changes, such as bronchopneumonia, spores, septate hyphae, and mild granulomatous inflammation, were also observed. At 14 dpi, multiple caseous nodules and plaques were found in the air sacs; plaque and necrosis in large areas of the lungs and severe multifocal granulomatous inflammation were noted.

Conclusion: The clinical symptoms of aspergillosis emerged at 3 dpi and gradually decreased beginning at 7 dpi. Similar pathological changes were observed in the air sacs and lungs. The results of this work provide additional information on the pathogenesis of aspergillosis.

Keywords: aspergillosis, broiler, clinical, pathological.