Mycoplasma Hyosynoviae Infection

Mycoplasma hyosynoviae infection

Description, Causes and Risk Factors:

Mycoplasma hyosynoviae infection affects pigs throughout the world. This organism has an affinity for joint tissue resulting in marked lameness, pain and economic losses. In the field it is difficult to determine if lameness in pigs is due to M. hyosynoviae infection, other infectious agents, or trauma.

Mycoplasma hyosynoviae is a small bacteria-like organism that is widespread within pig populations and is spread easily in infected pigs and by transfer of faeces. It is possible that it can spread on the wind.

Two other mycoplasmas are commonly seen in the pig - mycoplasma hyopneumoniae - the cause of the Enzootic pneumonia in pigs and the less frequently diagnosed mycoplasma hyorhinis, which can cause respiratory disease and occasional lameness.

It should be noted that these 3 agents are distinct with no known cross immunity. This, therefore, means that the widespread use of M. hyopneumoniae vaccines to control Enzootic pneumonia will have no protective effect against M. hyosynoviae infection and subsequent arthritis. No vaccines are available for the other two mycoplasmas.

M. hyosynoviae lives on the tonsils of many pigs and can get into the body and circulate in the bloodstream before settling into joints. It is also believed to be excreted in breath, saliva, and faeces. It will spread rapidly between pigs.


The clinical presentation of mycoplasm infection tends to vary with age and severity of infection. In younger growing pigs - typically 10 weeks old and above - lameness will be of sudden onset and within a group can range from partial lameness on a single limb through posterior recumbency to extreme cases of complete recumbency and inability to stand due to pain in swollen joints.

The other group of pigs particularly vulnerable to M. hyosynoviae infection is young adult breeding stock and in particular replacement gilts recently arrived on the farm.

Lameness tends to be more obvious in hind limbs but infection can occur in any joints in any limbs.

If the lower leg joints are affected, particularly the hock, then a visible soft fluid swelling may be felt. Swollen superficial may also be infected although this is likely to be of little clinical significance.


Mycoplasma hyosynoviae-specific complement fixation and ELISA assays have been described, although serology results are not always correlated to disease status. Culture is considered the gold standard for diagnosis of M. hyosynoviae, but results can take several days to weeks to obtain. Cultures are confirmed as M. hyosynoviae by a fluorescent antibody (FA) test or a disc growth inhibition test, although specific antibodies are not commercially available. Two polymerase chain reaction (PCR) assays targeting the 16S ribosomal RNA of M. hyosynoviae have been described, although limited data are available on their sensitivity when used on joint fluid or joint swabs. The purpose of this study was to compare results obtained by culture and PCR from clinical samples.

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.


A number of antibiotics are active against M. hyosynoviae, including the pleuromutilins, tiamulin and valnemulin, macrolides such as tylosin, lincosamides such as lincomycin, tetracyclines and the fluoroquinolones enrofloxacin.

Although M. hyosynoviae appears to be spread worldwide, fortunately, it does not cause a clinical problem of mycoplasmal arthritis in every herd. Stress, even in relatively immune carrier pigs, appears to be a major inducer of the infection, hence when boars and gilts are transported to new farms they break down with the disease. Prompt treatment by injection of clinical cases and good nursing to ensure they can get access to feed and water will help improve recovery. Metaphylactic treatment either in feed or water of new arrivals appears to control the disease developing well and hopefully this niggling disease can be avoided.

Preventive Measures:

    Identify the period of onset and apply strategic preventative medication.

  • In-feed medicate susceptible groups over the critical period with either 500-800g OTC (over-the-counter) 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

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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