Tuberculosis in Rhinoceros: An Underrecognized Threat?

Historical evidence of tuberculosis (TB) affecting primarily captive rhinoceroses dates back almost two centuries. Although the causative Mycobacterium tuberculosis complex (MTC) species has not been determined in many cases, especially for those that occurred before bacterial culture techniques were available, the spectrum of documented reports illustrates the importance of TB as cause of morbidity and mortality in different rhinoceros species across continents. In more recent years, sporadic suspected or confirmed cases of TB caused by Mycobacterium bovis (M. bovis) have been reported in semi-free or free-ranging rhinoceroses in South Africa. However, the true risk TB may pose to the health and conservation of rhinoceros populations in the country's large conservation areas where M. bovis is endemic, which is unknown. Underlying the current knowledge gap is the lack of diagnostic tools available to detect infection in living animals. As documented in other wildlife species, TB could establish itself in a rhinoceros population but remain unrecognized for decades with detrimental implications for wildlife conservation at large and should such animals be moved to uninfected areas or facilities. This paper reviews the current state of knowledge regarding TB in rhinoceros including critical gaps that need to be addressed to effectively assess the threat that this disease may present to rhinoceros.