Mycoplasma synoviae (MS) most often causes a subclinical infection in affected birds. It can also cause upper respiratory disease, reproductive disease, or on rare occasion, infectious synovitis, an acute to chronic infection of chickens and turkeys involving the synovial membranes of joints and tendon sheaths. Usually manifestation of disease is associated with a trigger or stressor.
Mycoplasma spp. are Mollicutes bacteria that lack a cell wall around their membrane, and as such, often unaffected by many common antibiotics that target cell wall synthesis. Antimicrobials commonly used to treat Mycoplasma spp. infections include tetracyclines, macrolides (tylosin, tilmicosin), and more recently, fluoroquinolones (enrofloxacin, difloxacin), and pleuromutilins (tiamulin).