Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 6, 1998
Publication Date: N/A
Technical Abstract: To examine the temporal development of tuberculous lesions in cattle, hereford cows were inoculated by intratonsilar instillation of 1.48x10*5 to 5.4x10*7 CFU of virulent Mycobacterium bovis. Tissues were collected 3 to 4 hrs, 4 wks, 6 wks,and 8 wks after inoculation. Lesions were not seen in cattle examined 3 to 4 hrs after inoculation. Medial retropharyngeal lymph nodes examined 4 wks after inoculation had cortical aggregates of macrophages without multinucleated giant cells or fibrosis. Medial or lateral retropharyngeal lymph nodes from all cattle examined 6 or 8 wks after inoculation had large coalescing granulomas with central areas of necrosis. These granulomas contained numerous macrophages, lymphocytes, plasma cells, and multinucleated giant cells. Fibrosis was revealed by Masson's trichrome staining around the granuloma periphery and around caseonecrotic debris. Cattle examined 6 or 8 wks after inoculation, had lesions in nonretropharyngeal sites including; mandibular, superficial cervical, prefemoral,tracheobronchial, mediastinal, and hepatic lymph nodes and lung. Granulomas can develop in draining lymph nodes in as little as 4 wks after intratonsilar inoculation. Morphologic changes in granulomas indicate increased cellular chemotaxis and differentiation. Spread of infection occurred by lymphatic and hematogenous routes to distant sites after establishment of primary infection in retropharyngeal lymph nodes.