Also known as M.g, Mycoplasma gallisepticum is an infection which can affect chickens, turkeys, game birds, pigeons and other wild birds. Ducks and geese can also become infected if kept in close proximity to chickens.

M.g. is less evident in birds kept commercially due to single age sites and high levels of biosecurity. However, in extensive flocks where there are multiple age groups and exposure to wild birds, M.g. is relatively common.

The route of infection is via the conjunctiva or upper respiratory tract. The incubation period is 6-10 days. Transmission can be through the egg from the breeder birds or directly bird to bird through dust, feathers, aerosols, faeces and vectors such as equipment. Birds can recover from M.g. but will remain infected for life; subsequent stress may cause reoccurrence of disease.


  • Coughing/sneezing
  • Nasal and ocular discharge
  • Poor productivity
  • Slow growth/stunting
  • Leg problems
  • Morbidity and mortality
  • Inappetance
  • Reduced hatchability and chick viability
  • Occasional encephalopathy and abnormal feathers

The infectious agent survives only a few days, but has been shown to live longer on the feathers. M. g. can be transmitted by humans on hair and in the nostrils. Predisposing factors for clinical disease are the presence of respiratory viruses (IB/ND/ART), other disease and challenging environmental conditions.


M.g. needs to be confirmed by taking blood samples of a flock to check if the birds are positive. Subsequent blood samples may be necessary. Post mortem examination alone is not sufficient to diagnose this disease, although there are PCR test available to diagnose the presence of the genetic material in infected organs


There are some antimicrobial treatments available which will help in the control of M.g. but they will often not eradicate it from the site.


Biosecurity and good management practices are essential. Reduction of multiple age groups, low stocking densities, alongside implementing a vaccination programme, operating a closed flock where possible, antimicrobial treatments and reducing exposure to wild birds.

Article Taken from The Chicken Vet

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