Macrorhabdus ornithogaster, also known as “megabacterium” or avian gastric yeast (AGY), is a novel anamorphic ascomycetous yeast that belongs in its own new genus, with a worldwide distribution1,2,3,4. Megabacteria has been found in both psittacine and passerine species, both in captivity and in the wild. It is usually found colonizing the mucosal surface of the isthmus existing between the proventriculus and ventriculus5 of a wide diversity of bird species and currently represent a potential threat to bird breeders. Clinical signs include weight loss in spite of a good appetite, regurgitation, diarrhea, depression, maldigestion, ruffled feathers and death3,6. The main purpose of this study was to assess the presence of this yeast in breeding canaries (Serinus canaria) distributed in Piedmont.