Emergencies/Illness Health Issues

Mycoplasma Synoviae

Infectious Synovitis is a bacterial disease affecting chickens caused by Mycoplasma Synoviae (MS). It causes a wide variety of damage to joints, tendons, tissues, organs and the respiratory system. Historically it was seen as a disease which affected the synovial membrane of joints and tendons, but is now becoming more common in multi-age flocks presenting as an upper respiratory tract illness. Birds can be infected and appear healthy until stressed, which then triggers systemic symptoms.


  • Lethargy, depression
  • Decreased appetite
  • Ruffled feathers
  • Stunted growth
  • Green poop
  • Pale or bluish comb
  • Breast blisters
  • Decreased egg production
  • Poor egg quality (thinning at the wide end)
  • Swollen, red and warm hocks, shanks and feet
  • Fluid retention in hock joints
  • Difficulty walking
  • Mild tracheitis, sinusitis or airsacculitis (often seen in conjunction with Newcastle Disease or Infectious Bronchitis)


  • Can be spread by chickens, turkeys, wild birds or rodents
  • Spreads vertically from hens to chicks (via egg) and between birds of all ages within a flock
  • Direct spread through poop, aerosolized droplets between birds to the eyes or upper respiratory tract
  • Indirect spread between flocks via fomites (shoes, clothes, equipment)
  • MS remains infectious in the environment for several days
  • Incubation period 11- 21 days
  • Risk factors include stress and pre-existing viral respiratory infections
  • Seen as a complication of airsacculitis in co-infection with Newcastle disease or Infectious Bronchitis.
  • High infection, but low death, rates


  • Injectable forms of antibiotics such as tylosin, erythromycin, spectinomycin or chlortectracycline are more effective than those administered in drinking water or feed.
  • Antibiotics will decrease symptoms, cut recovery times and prevent new transmissions, but are not a cure. All infected birds (even those who are asymptomatic) are considered carriers for life.
  • Chronically infected chickens are more vulnerable to contracting other pathogens like Newcastle Disease, Infectious Bronchitis or other bacterial infections.


Although MS is less common than its cousin Mycoplasma Gallisepticum the prevention strategies are the same:

  • Purchase birds from a known MS-free flock (NPIP in the USA)
  • Practice all-in, all out flock management
  • Adhere to strict biosecurity
  • Minimize stress
  • Boost your flocks’ immunity with a balanced feed
  • Quarantine new birds
  • Minimize contact with wild birds and rodents (keep feed inside the coop, pick up dropped feed)
  • Vaccines are not widely available

Credits: Merck Veterinary Manual, Poultry DVM & the Florida Department of Agriculture.

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