Mycoplasmosis is an infectious disease caused by bacteria of the genus mycoplasma. Mycoplasma gallisepticum bacteria colonize the mucous membranes of chickens and lead to sniffles and breathing problems in the first instance. Often, chicken carry mycoplasmas without an outbreak of the disease or only a mild form of the upper respiratory tract. Only additional factors, such as lack of hygiene, vaccination viruses and E.coli infections (secondary infections) which weaken the immune system of the chicken, then lead to an outbreak of the chronic and epidemic disease mycoplasmosis.


Mycoplasmosis is much more common in large fattening farms than in small, private chicken farmers. Chicken farmers in the private sector have less of a problem with hygiene. The chickens become infected much more at exhibitions or by already, not noticeably diseased, additionally bought animals.

Most importantly, the transfer of the mycoplasma from the mother to the hatching egg and thus to the progeny has to be considered. Air and contact transmissions are also possible.


With an incubation period of 10-30 days, mycoplasmosis in chickens breaks out rather slowly. As in most cases of chicken diseases, this infection mainly affects young animals aged 4-8 weeks.

It comes to an inflammation of the air sac and pericardium which will quickly lead to death.

Sick chickens show the following discernible symptoms:

  • Severe sniffles
  • The laying performance of the hen decreases significantly
  • A sick cock crows little to no more
  • Conjunctivitis in chicks
  • Nasal and eye discharge
  • Sniffing, smacking breathing noises, beak breathing
  • Declining appetite, resulting in poorer growth rate in chicks and young animals (fattening farm)
  • Unkempt plumage
  • Infections of the lower eye cavity, often described as an “owl-like appearance”
  • Deaths, especially in chicks and young animals

The pathogen is usually detected by a PCR test.


If a chicken population is only slightly infected with mycoplasma, a broad-spectrum antibiotic is sufficient for treatment. However, the chickens will never again be free of pathogens, even if they are treated several times. Already infected chickens could repeatedly lead to new infections among the chicks.


Mycoplasmosis prevention through active immunisation (vaccination), adequate hygiene and targeted slaughter of already infected chickens is much more effective.

In general, the current breeding flocks of chickens are free of mycoplasmosis.

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