Pathology and diagnosis of Mycobacetrium bovis infection in dromedary camels

Tuberculosis was diagnosed at necropsy in six camels having age varying from one to ten years. Clinically these camels were not showing any respiratory symptoms however they showed signs of anorexia, emaciation, fever, frequent lachrymation, lethargy and weakness since past 1 to 5 months. The necropsy of these camels revealed pulmonary tuberculosis in five camels and milliary or disseminated tuberculosis in one camel. Grossly the tuberculous lesions in lungs were multifocal to coalescing, white, nodular and calcified of different diameters (from 2 mm to 10 cm). The pea sized nodules containing caseous and calcified mass were also found scattered and attached to pleura and internal rib surface. The mediastinal lymph nodes were enlarged, hard, calcified and severely congested. The impression smear from lung and mediastinal lymph nodes stained with Ziehl-Neelsen stain showed pink acid fast bacilli. The tuberculous lesions from lung and mediastinal lymph nodes were cultured on LJ media slants which showed typical cream colonies of Mycobacterium bovis after 10–15 days of incubation. The lung, mediastinal lymph node tissues and colonies from culture were used for DNA extraction and PCR for amplification of hupB gene of M. bovis. All samples were found positive for amplification of hupB gene showing band at 645 bp. Histopathology of lung and mediastinal lymph nodes showed typical granulomatous lesions with central area of caseous necrosis surrounded by lymphocytes, epithelioid cells, occasional giant cells and layer of fibrous tissue. The acid fast bacilli were demonstrated in lung and mediastinal lymph nodes by Ziehl-Neelsen stain