Mycoplasma gallisepticum (MG) is a bacterium in the class Mollicutes and the family Mycoplasmataceae. It causes chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys, chickens, game birds, pigeons, and passerine birds of all ages. Mycoplasma gallisepticum is a significant pathogen in poultry.
Mycoplasma gallisepticum causes respiratory disease and weakens the immune system which makes the bird vulnerable to any disease that they come into contact with. Small bubbles will appear in the corners of the eyes and sinuses will swell up. Once infected, they are carriers for the disease for life. Some birds have good resistance to the disease while others may die; some become ill and recover and others may not show any symptoms at all. There is currently no risk to humans. For domestic animals, there is a high concern and there should be a prevention of any interaction between wild birds and domestic poultry. Wild bird species affected by the disease are infectious and are often found in close contact with domestic species.