EXPERIMENTAL BRUCELLA-ABORTUS STRAIN 19 ARTHRITIS IN YOUNG CATTLE

Several reports have shown an association between lameness in cattle a nd vaccination with Brucella abortus strain 19. Affected joints are cu lture negative for Brucella, but the synovial fluid is positive for B. abortus antibodies. The joints contain cloudy fluid, with villous pro liferation of the synovium. Brucella abortus antigens are often found in the synovium with fluorescent antibody staining. This report descri bes the experimental reproduction of a chronic synovitis in 6 young An gus steers using intra-articular injections of B. abortus strain 19. T he carpal and tibial joints were injected with 5 x 10(9) colony-formin g units/ml of B. abortus strain 19 and regularly biopsied over a 28-da y period. Steers started becoming serologically positive for B. abortu s on post-inoculation day (PID) 5 and were all positive by PID 7. Join ts were cultured and examined by fluorescent antibody staining, immuno histochemical methods, and light and transmission electron microscopy. Lesions typical of the field cases were present by PID 21. Brucella a bortus was cultured more often during PID 1-5 (6 of 9 joints) than dur ing PID 7-28 (3 of 15 joints). Brucella abortus was only found on PID 1 and 5 by fluorescent antibody staining and in only 2 joints immunohi stochemically on PID 5 and 7. The reproduction of lesions typical of f ield cases but the inability to locate B. abortus antigens in the syno vium raises the question of whether in field cases the synovium is con tinually or intermittently seeded with bacteria or if factors other th an just the bacterium are needed to perpetuate the lesion.