_1685865345 20230604075545000 Rovedar Daryoushbabazadeh@gmail.com Rovedar Journal of World’s Poultry Science J. World's Poult. Sci. 2980-7999 09 25 2022 1 1 Muhammad H Kafrashi Daryoush Babazadeh https://orcid.org/0000-0003-1118-2295 Introduction: The avian gastric yeast (Macrorhabdus ornithogaster) is a microorganism that infects aviary birds worldwide and can cause chronic wasting disease. Macrorhabdus ornithogaster, previously named Megabacter, infects a large group of companion birds, such as cockatiels, budgerigars, lovebirds, parrots, african gray parrots, and green-cheeked parakeets. The aim of the present case study was to evaluate the infection by Macrorhabdus ornithogaster in some companion birds and to show their prospects in the future. Case report: The investigated species included 145 cockatiels, gray parrots, lovebirds, green cheeks, and budgerigars with symptoms, such as lethargy, weight loss, regurgitation, and gasping referred to the Aria Veterinary Hospital, Mashhad, Iran, during 2021-2022. The samples were randomly evaluated for gastric yeast (Megabacter) using the gram-staining method of their feces. Conclusion: The results revealed that almost half of the symptomatic cases showed active or non-active yeast in their slides. A 14-day treatment of nystatin, apple vinegar, and metronidazole was applied for all cases, and then gram-staining slides were tested after three weeks showing that the treatment was successful. However, infection recurrence was detected in several birds, suggesting food hygiene control. 12 25 2022 29 31 https://creativecommons.org/licenses/by/4.0 10.58803/jwps.v1i1.5 https://jwps.rovedar.com/index.php/JWPS/article/view/5 https://jwps.rovedar.com/index.php/JWPS/article/download/5/6 https://jwps.rovedar.com/index.php/JWPS/article/download/5/6