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To examine the temporal development of tuberculous lesions in cattle inoculated with Mycobacterium bovis.


15 mature crossbred cows obtained from a herd with no history of M bovis infection.


Inoculation of cattle was done by intratonsilar instillation of 1.48 × 105 to 5.4 × 107 colony-forming units of M bovis strain 2045T. At 3 to 4 hours, 4 weeks, 6 weeks, and 8 weeks after inoculation, tissues were examined for gross and microscopic lesions and processed for isolation of M bovis.


Retropharyngeal lymph nodes from cattle examined 4 weeks after inoculation contained microgranulomas consisting of aggregates of macrophages with few neutrophils. Retropharyngeal lymph nodes from all cattle examined 6 and 8 weeks after inoculation contained multiple, large, coalescing granulomas consisting of central areas of necrosis with mild fibrosis, numerous macrophages, lymphocytes, plasma cells, multinucleated giant cells, and neutrophils. Three of 8 cattle examined 6 or 8 weeks after inoculation had lesions in nonretropharyngeal sites with morphologic characteristics similar to that seen in retropharyngeal lymph node granulomas from cattle examined 4 weeks after inoculation.


Granulomas can develop in draining lymph nodes of cattle in as little as 4 weeks after inoculation via intratonsilar instillation of M bovis. Intralesional morphologic changes between 4 and 6 weeks after inoculation indicate an increase in cellular chemotaxis and differentiation. Dissemination of bacteria to distant sites most likely was by lymphatic and hematogenous routes after establishment of the primary infection in retropharyngeal lymph nodes. (Am J Vet Res 1999;60:310–315)

Free access
in American Journal of Veterinary Research


A study to determine and compare the sensitivity of the caudal fold tuberculin test (cft) and a commercial γ-interferon (γ-ifn) assay for diagnosis of bovine tuberculosis was conducted. A dairy herd with approximately a third of the cattle infected with Mycobacterium bovis was chosen for this study. All cattle from this herd were slaughtered, and tissue specimens for bacteriologic culturing and histologic examination were collected. Results of the cft and γ-ifn assay were compared with results of bacteriologic culturing and histologic examination to determine test sensitivity. Results were analyzed, using each of the following 4 standards to classify cattle as infected: positive test result by bacteriologic culturing only; histologic examination only; bacteriologic culturing and histologic examination; and bacteriologic culturing or histologic examination. Sensitivity of the cft ranged from 80.4 to 84.4%, depending on the standard of comparison. Sensitivity of the γ-ifn assay ranged from 55.4 to 97.1%, depending on the standard of comparison and on the method of interpretation. The cft was significantly (P < 0.001) more sensitive than the γ-ifn assay for diagnosis of bovine tuberculosis when the γ-ifn assay was conducted and interpreted as instructed by the manufacturer. Maximum overall sensitivity was achieved when results of the cft and γ-ifn assay were interpreted in parallel.

Free access
in American Journal of Veterinary Research