Submitted to: International Congress on Anthrax, Brucellosis, CBPP, Mycobacterial Disease
Publication Type: Proceedings
Publication Acceptance Date: May 1, 1998
Publication Date: N/A
Technical Abstract: Development of tuberculous lesions in 15 hereford cattle was examined by instillation of 1.48x10*5 to 5.4x10*7 CFU of Mycobacterium bovis into the crypt of the palatine tonsils. Cattle were examined and tissues collected 3 to 4 hrs, and 4, 6, and 8 wks post-inoculation (PI). Lesions were not seen in cattle examined 3 to 4 hrs PI. Medial retropharyngeal (Med rph) lymph nodes (LNs) from 2 of 3 cattle examined 4 wks PI had cortical aggregates o macrophages and fewer neutrophils (microgranulomas) but without multinucleated giant cells or fibrosis. Med rph LNs from 4 of 4 cattle examined 6 wks PI had granulomas that were large, multiple, and coalescing with central areas of necrosis. These granulomas contained numerous macrophages, lymphocytes, plasma cells, multinucleated giant cells, and variable numbers of neutrophils. Fibrosis was revealed by Masson's trichrome staining around the periphery of the granuloma and around caseonecrotic debris. Two cattle examined 6 wks PI had lesions in non-rph sites including: mandibular, superficial cervical, and prefemoral LNs, and lung. Four of 4 cattle examined 8 wks PI had granulomas in med or lateral rph LNs similar to those described at 6 wks after inoculation. One cow also had granulomas within the tracheobronchial, mediastinal, and hepatic LNs. Morphology of granulomas in non-rph sites in cattle examined at 6 and 8 wks PI was similar to those in rph LNs from cattle examined 4 wks PI. Granulomas can develop in draining LNs in as little as 4 wks after intratonsilar inoculation. Morphologic changes in granulomas between 4 and 6 wks PI indicate an increase in cellular chemotaxis and differentiation. Spread of infection occurred by lymphatic and hematogenous routes to distant sites after establishment of primary infection in rph LNs.