Factors such as drought might play a role in altering susceptibility to infection, considering no positive culture results were obtained in >20 rhinoceros carcasses examined before June 2016.Īlthough disease and death associated with bovine TB have not been observed in white rhinoceroses, M. However, no cases of disseminated bovine TB have been observed in this species, supporting the authors’ hypothesis that the disease in white rhinoceroses is self-limiting. In our study, collection of samples with minimal degradation was facilitated by our examining only rhinoceroses dead for 1 tissue sample in the same rhinoceros suggests infection rather than contamination. bovis infection in these animals.įresh samples from animals that die naturally are difficult to locate in a large ecosystem, especially before predators arrive at the carcass or decomposition occurs due to elevated temperatures. Further research is required to understand the pathogenesis and epidemiology of M. bovis infection did not regularly shed bacilli ( 10). Although no data were available to evaluate transmission, a previous study has shown white rhinoceroses with localized M. bovis was also isolated from mesenteric and peripheral lymph nodes ( Table). Location of lesions yielding positive cultures suggests an aerosol route of exposure, although M. However, whether infected animals would develop disease if compromised is unknown. The low number of positive cases and localized paucibacillary lesions support the hypothesis that white rhinoceroses, although susceptible to infection, are able to limit disease progression ( 10). The timing of infections suggests that animals under nutritional stress might be more susceptible to infection, similar to observations in other species ( 9). ‡No clinically significant lesions other than inflammation (poaching case).įour of the infected animals were found during September–November 2016, near the end of the drought, and the remaining 2 animals were found in September and October 2017, at the end of the next winter. †LNs were pooled into 4 sets: head (retropharyngeal, submandibular, and cervical) thoracic (tracheobronchial and mediastinal) abdominal (mesenteric and hepatic) and peripheral (axillary, prescapular, and inguinal) LNs. *AFB, acid-fast bacilli LN, lymph node ND, not done TB, tuberculosis + feature present – feature absent. Tracheobronchial, prescapular, and retropharyngeal LNs and lung + Lung and prescapular, retropharyngeal, and tracheobronchial LNs – Lung + submandibular, retropharyngeal, tracheobronchial, and mesenteric LNs Head, thoracic, and peripheral LNs and lung Macroscopic, multifocal mineralized granulomas bovis isolates as strain SB0121, the most common strain found in KNP ( 8).įeatures of lesions consistent with bovine TB† On histologic examination, we found granulomatous inflammation in lung or lymph node sections and rare acid-fast organisms in some granulomas ( Table). Grossly visible lesions, mostly found in the retropharyngeal or tracheobronchial lymph nodes or lung, were typically small and localized and could easily be missed or mistaken for granulomas caused by other pathogens if careful dissections of tissues were not performed ( Technical Appendix). bovis infection in 6 white rhinoceroses ( Table). bovis infection were found in black rhinoceroses. Research protocols were approved by the South African National Park Animal Use and Care Committee and ethics committee of Stellenbosch University. To determine which animals were infected, we conducted macroscopic examinations and collected samples for histopathologic studies and mycobacterial culture, as previously described ( 7). Thereafter, a surveillance program was initiated to screen rhinoceros carcasses in KNP, leading to 35 white and 5 black rhinoceros carcasses being examined during June 2016–October 2017. In June 2016, a black rhinoceros ( Diceros bicornis minor) with an M. However, prolonged drought in South Africa (2015–2017) raised concerns that starvation and disease could increase the mortality rate and affect conservation efforts for this species ( 5). KNP contains the largest free-living population of white rhinoceroses in the world (estimated at 6,649–7,830). Bovine TB is endemic in many wildlife populations worldwide, including among those in Kruger National Park (KNP), South Africa ( 4). bovis has been reported in captive rhinoceroses since the early 1800s ( 1 – 3). Tuberculosis (TB) caused by Mycobacterium tuberculosis or M.
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