Polyarthritis of Lambs Induced Experimentally by a Psittacosis Agent

The specific effects on synovial and other joint tissue of a psittacosislymphogranuloma venereum agent isolated from synovial fluid of lambs with polyarthritis were investigated in 5 to 6-month-old lambs. All intra-articularly, intravenously, and intramuscularly inoculated lambs developed stiffness and lameness after inoculation and had polyarthritis and tendovaginitis at necropsy. When inoculation was made directly into a joint of a lamb, the agent was detected in the blood and other joints 3 days after exposure. Reconvalescent sheep did not develop polyarthritis but still harbored the psittacosis-lymphogranuloma venereum agent 21 days after inoculation. The synovial membranes of all inoculated young lambs developed lesions that were identical to those characterizing naturally occurring cases. The subsynovial connective tissue contained numerous granulomatous accumulations with large numbers of mononuclear cells. Fibrin, leukocytes, synovial cells, monocytes, lymphocytes, and nuclei were found in the greyish yellow joint fluid taken from affected joints. The numbers of such cells per mm 3 of joint fluid varied from 1000 to 52,000. The synovial fluids of the control lambs and the reconvalescent sheep were rather acellular.