Mycoplasma synoviae (MS) is a bacterial pathogen that infects poultry, primarily chickens and turkeys. Unlike respiratory diseases that only affect the lungs or sinuses, MS is known for its ability to infect both the respiratory tract and the joints, leading to lameness, swollen joints, and reduced egg production in layers.

MS is part of the Mycoplasma genus — meaning it lacks a cell wall, which makes it harder to treat with common antibiotics and highly persistent once introduced into a flock.

MS often starts with mild respiratory signs like nasal discharge, coughing, and sneezing. In more advanced or complicated cases, it can spread to the synovial membranes in the joints, causing:

• • Swollen hocks and footpads

  • Lameness or reluctance to walk

• Decreased feed and water intake

MS can also infect the reproductive tract, leading to:

• • Thin-shelled or misshapen eggs

  • Reduced egg production in hens

  • The bacteria are transmitted both horizontally (bird-to-bird via droplets) and vertically (from hen to egg).