Mycoplasma Arthritis

This disease primarily affects gilts. The key clinical signs include reluctance to rise; lameness; pigs appear in pain.
calendar icon 15 November 2018
clock icon 7 minute read

Background and history

This is caused by the organism Mycoplasma hyosynoviae which is ubiquitous and most herds are infected with it. It is a respiratory disease, the organism being found in the upper respiratory tract nose and tonsils. It may be present in some herds and cause no clinical signs and yet in others cause severe disease.

It is spread by droplet infection. It invades the joints and tendon sheaths of susceptible animals and causes lameness and swelling.

Older sows develop a strong immunity which they pass to their offspring in the colostrum. Infection takes place sometime after this colostral immunity has worn off, usually between 12 and 30 weeks of age. Sometimes gilts do not become infected until introduced to a new herd or in early pregnancy.

It is common in purchased gilts which have been reared in isolated grow-outs, but uncommon in mature sows. It is more common in the heavy ham straight legged animal.

Infection with or without disease takes place in the growing pig from approximately 8 to 30 weeks of age.

Similar diseases include muscle damage, leg weakness or OCD, trauma, erysipelas, glässers disease and the major vesicular diseases.

Clinical signs

  • Starting with a reluctance to rise.
  • Lameness.
  • Swellings over hock joints visible.
  • Affected pigs are in pain and only stand for short periods.
  • The temperature may be slightly elevated.
  • Shivering.

Clinical signs in the gilt are sudden in onset.


This is based on clinical signs and the response to either lincomycin or tiamulin therapy. Joint fluid can be aspirated and examined for antibodies and the organism can be isolated.

Serology is not much help because sub-clinical infection is common and so healthy animals often have antibody titres. Rising titres in blood samples taken two weeks apart aid diagnosis.

Post-mortem examination may be necessary to reach a definitive diagnosis.

It must be differentiated from the similar conditions listed above.


  • The quality of housing – in particular low temperatures and draughts which act as trigger factors.
  • Mixing and fighting.
  • Respiratory spread.
  • High stocking density.
  • Sudden reduction in energy intake producing stress nutritional changes.
  • Poor ventilation.


Mycoplasma hyosynoviae can be a recurring problem in breeding gilts particularly during the first 6 to 10 weeks after introduction to the farm. Consider the following:

  • Identify the period of onset and apply strategic preventative medication.
    • In-feed medicate susceptible groups over the critical period with either 500–800g OTC or CTC per tonne, 110–220g of lincomycin per tonne or 100g of tiamulin per tonne.
An alternate strategy is to medicate the ration at half these levels and feed for 5–7 weeks. Maintain pigs on ad lib feeding during the susceptible period. Assess the quality of housing – in particular low temperatures and draughts which act as trigger factors. Remember that this is a respiratory spread disease and other factors need to be considered. Avoid mixing and fighting. Provide well bedded pens. In outdoor herds acclimatise gilts to cobs or large nuts before they are introduced into the outdoor herd. Control enzootic pneumonia and other respiratory diseases if they are a coincidental problem.


Treatment is most effective if given early.

  • Mycoplasma hyosynoviae is susceptible to lincomycin or tiamulin injections.
  • Give daily for four days in the early course of the disease. If the lameness is due to Mycoplasma hyosynoviae there should be a good response within 24 to 36 hours.

Emily Houghton

Editor, The Pig Site

Emily Houghton is a Zoology graduate from Cardiff University and was the editor of The Pig Site from October 2017 to May 2020. Emily has worked in livestock husbandry, and has written, conducted and assisted with research projects regarding the synthesis of welfare and productivity of free-range food species.

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