In fattening pigs osteoarthritis commonly results from
M. hyosynoviae infection or in some cases by trauma.
M. hyosynoviae infection may increase production costs arising from treatment, labour and culling. Development of disease involves M. hyosynoviae exposure through inhalation of the organism. Within two days the organism spreads via the blood stream and may persist in the circulation for 8-10 days prior to its delivery to the joints. The infected pigs may not have any lesions or display severe arthritis; overweight pigs may have more severe symptoms.
The clinical signs become noticeable between 12-24 weeks of age and may involve lameness. It may affect one or more than one leg especially of the hind limbs. However swollen joints may not be noticeable due to the affected joints being covered with muscle. If the affected joints are the hock joints with less muscular covering joint enlargement may be seen easily. Acute clinical signs can remain for about 10 days and many infected pigs will recover and walk normally. In cases where lameness persists the pigs will develop osteoarthritis and will be culled later.
The mortality rate is low whilst the morbidity may vary from 1% - 50%. Affected pigs are usually injured by their pen mates or have secondary infections.
Gross lesions caused by M. hyosynoviae may occur in one or several joints and are frequently found at the shoulder, elbow, stifle and hock joints.
| 
