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Mycoplasma Arthritis (Mycoplasma Hyosynoviae Infection)

(435) This is caused by the tiny organism Mycoplasma hyosynoviae which is ubiquitous and most, if not all herds are infected with it. It is a respiratory spread 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. Infection with or without disease takes place in the young growing pig from approximately 8 to 30 weeks of age and particularly so in the gilt when first introduced onto a farm, or in the early stages of pregnancy. It is very uncommon in older sows because they develop a strong immunity resulting from repeated exposure to the organism. They pass this immunity to their offspring in the colostrum. This maternally derived immunity gradually disappears over a period of weeks. Infection then takes place as these pigs become exposed to older ones. Mycoplasma hyosynoviae infects joints and tendon sheaths rather than the respiratory system.

Clinical signs

Disease in the gilt is usually sudden in onset, the first signs being a reluctance to rise at feeding time. There is a considerable amount of pain and the affected pig will only stand for short periods of time. The temperature may be normal or slightly elevated. It is more common in the heavy ham straight legged animal and purchased gilts which have been reared in isolated grow out units often become diseased four to six weeks after arrival.


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 isolation of the organism.

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 together with typical symptoms strongly suggest disease.

In problem herds post-mortem examination may be necessary to reach a definitive diagnosis.

Similar diseases

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


  • Mycoplasma hyosynoviae is susceptible to lincomycin or tiamulin injections.
  • Give daily for 4 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.
  • Treatment is most effective if given early.
  • Give in feed medication strategically commencing 7 days before the expected disease outbreak and continue for 14 days using 220g/tonne of lincomycin, 500-800g/tonne of OTC or 100g/tonne tiamulin.
  • An alternate strategy is to medicate the ration at half these levels and feed for 5-7 weeks.
Management control and prevention

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.
  • 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.

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