Arthritis in pigs induced by dietary factors. Microbiologic, clinical and histologic studies.

Eight-week-old pigs fed a protein-rich diet developed an abnormal intestinal microbial flora within 1 week. The main feature was a significant increase in the number of atypical , type A. In the first week after the change of diet, the pigs showed disturbances of movement and swollen peripheral joints. The ESR was concomitantly elevated and later on hypergammaglobulinaemia with increased antibody titres to antigens were noted. Joint deformities were observed after some months. The joint lesions consisted of synovitis with a cell-rich exudate. The lesions of the synovial tissue were characterized by proliferation of the synovial lining cells with villous hypertrophy and highly vascularized granulation tissue containing accumulations of lymphoid cells. Pannus formation and erosion of joint cartilage were seen in some animals. Bacteriological examination, including search for mycoplasmas, was negative. Subcutaneous nodules of rheumatoid nature were also found. Signs of proliferative glomerulonephritis were demonstrated in most of the animals. Different pathogenic aspects are discussed with regard to the direct influence of antigens on the joint tissues, circulating antigen–antibody complexes and cell-bound antibodies. As the same abnormal intestinal flora and immunological reaction to intestinal have been found in human rheumatoid disease, this diet-induced pig arthritis of remarkably similar clinical and histological characteristics is of special interest.