Abstract
Background:
Avian aspergillosis is primarily a respiratory disease that can spread to other organs, resulting in systemic aspergillosis.

Aim:
This report describes the clinical and pathological features of multisystemic aspergillosis caused by Aspergillus fumigatus in a meat turkey flock, including an unusual case of vertebral Aspergillus osteomyelitis.

Methods:
Five affected turkeys were necropsied from a flock size of 1,000 birds. Gross lesions were recorded, and samples from affected organs were sampled for histopathological examination. Tissue sections were stained with hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS). Microscopic examination of morphological features was performed to identify the causative agent isolated from fungal cultures on Sabouraud Dextrose Agar (SDA).

Results:
The affected turkeys exhibited symptoms such as respiratory distress, open-beak breathing, prostration, cyanosis, lethargy, anorexia, and weight loss. Postmortem examinations revealed whitish-yellow caseous nodules in multiple organs, including the lungs, air sacs, thoracic vertebrae, heart, liver, pancreas, spleen, peritoneum, small intestine, proventriculus, gizzard, and kidneys. Histopathological analysis showed granulomas with a necrotic core surrounded by lymphocytes, plasma cells, macrophages, and large multinucleated foreign-body giant cells. Periodic acid-Schiff (PAS) staining revealed abundant fungal hyphae within the necrotic center. Fungal culture on Sabouraud dextrose agar and subsequent morphological identification confirmed the presence of Aspergillus fumigatus.

Conclusion:
To our knowledge, this is the first documented case of thoracic vertebral aspergillosis in turkeys. Future studies are needed to assess the prevalence of this mycosis in Algerian turkey flocks.

Key words: Aspergillus fumigatus, Histopathology, Multisystemic aspergillosis, Turkey, Vertebral osteomyelitis