Field studies on the association between amyloid arthropathy and Mycoplasma synoviae infection, and experimental reproduction of the condition in brown layers.

Approximately 20% of outbreaks of amyloid arthropathy in The Netherlands were earlier attributed to Enterococcus faecalis but there was no explanation for the remaining cases. In a further study, material from the joints of 10 birds from each of 10 affected brown layer flocks and two broiler flocks was cultured in several bacteriological media. E. faecalis was isolated from one layer flock but Mycoplasma synoviae was recovered from purulent joints in six of the layer flocks and both broiler flocks. Brown layers were then infected experimentally with one of the M. synoviae isolates to assess its arthropathic and amyloidogenic potential. Using Congo red staining, articular amyloid deposits were seen 12 weeks after intra-articular or intravenous inoculation in almost all birds. After intra-articular inoculation of the left knee joint the contralateral hock tendon sheath tended to be affected, while hock and foot joints were mainly affected after intravenous inoculation. Amyloid deposits were seen in livers and spleens of many birds. This is the first demonstration of arthropathic strains of M. synoviae with an association with amyloid arthropathy, while for one isolate its amyloidogenic potential was shown experimentally.