Bovine tuberculosis in a nebraska herd of farmed elk and fallow deer: a failure of the tuberculin skin test and opportunities for serodiagnosis

Abstract

In 2009, Mycobacterium bovis infection was detected in a herd of 60 elk (Cervus elaphus) and 50 fallow deer (Dama dama) in Nebraska, USA. Upon depopulation of the herd, the prevalence of bovine tuberculosis (TB) was estimated at ∼71-75%, based upon histopathology and culture results. Particularly with elk, gross lesions were often severe and extensive. One year ago, the majority of the elk had been tested for TB by single cervical test (SCT), and all were negative. After initial detection of a tuberculous elk in this herd, 42 of the 59 elk were tested by SCT. Of the 42 SCT-tested elk, 28 were TB-infected with only 3/28 reacting upon SCT. After SCT, serum samples were collected from the infected elk and fallow deer from this herd at necropsy and tested by three antibody detection methods including multiantigen print immunoassay, cervidTB STAT-PAK, and dual path platform VetTB (DPP). Serologic test sensitivity ranged from 79 to 97% depending on the test format and host species. Together, these findings demonstrate the opportunities for use of serodiagnosis in the rapid detection of TB in elk and fallow deer.

Figure 1

Gross lesions in elk. (b) demonstrates a tuberculous thoracic lesion that has eroded through the body wall. (a) demonstrates coalescing, multinodular, pulmonary granulomas. Orientation of both photographs: cranial to the left and dorsal to the top.

Figure 2

Microscopic lesions in elk. The image is a photograph of a representative pulmonary granuloma in an elk (hematoxylin and eosin stain). Note the large number of neutrophils and the single multinucleate giant cell in the center of the image. The inset image demonstrates an acid-fast bacillus (Ziehl-Neelson stain) in a pool of proteinaceous fluid, necrotic cell debris, and degenerate neutrophils.

Figure 3

Antibody responses to recombinant and native antigens detected in elk (a) and fallow deer (b) using a multiantigen print immunoassay. Numbers in lower margins indicate unique animal identification designations. Antigens printed on nitrocellulose are indicated in the right margin. E6/P10 refers to a fusion protein of ESAT-6 and CFP10. 16/83 refers to a fusion protein of the 16kDa protein and MPB83. F10 is a fusion protein consisting of CFP10, secE2, and PhoS1/pstS. B-PPD refers to M. bovis-derived purified protein derivative. MBCF refers to M. bovis-derived culture filtrate antigen.