Aspergillosis affects all types of birds causing the loss of specimens with high ecological value and also, it has a significant economic impact in the poultry industry. The main etiological agent is Aspergillus fumigatus, a filamentous fungus with multiple virulence factors, including gliotoxin (GT), which is an immunosuppressive epipolythiodioxopiperazine molecule. Necropsy was performed in 73 birds with different backgrounds that had shown respiratory semiotics compatible with aspergillosis. Mycological cultures of lungs with several lesions belonging to disease birds were performed. Additionally, a GT chloroformic extraction, a Thin Layer Chromatography analysis (CCF) and histopathology with hematoxylin-eosin and Grocott stainings were applied. The identification of A. fumigatus was confirmed by the polymerase chain reaction technique (PCR), amplifying the ITS 1 5.1-5.8S-ITS 2 fragment from the rDNA complex. In vitro GT production was studied in the recovered isolates of A. fumigatus by CCF. Seven A. fumigatus isolates were obtained; in six of them, similar compounds to GT were detected. In a lung sample, a compound with the same retention time (RF) as the GT reference was detected; whereas in three lung samples several compounds were observed, which had a different RF in comparison to the GT standard.