Tuberculosis as an Emerging (Re-Emerging) Disease in South African Wildlife
Bovine tuberculosis (BTB) has been recognized as a threat to wildlife health in South Africa since the 1990’s when veterinarians in Kruger National Park identified cases in buffalo herds in the southern area of the park. However, sporadic cases of BTB have been reported throughout the country since the initial identification in a greater kudu and common duiker in the Eastern Cape in 1929. Since that time, Mycobacterium bovis has been found in more than 21 species in South Africa.
Although a Bovine TB Eradication Scheme was introduced in 1969 to address the issue in cattle, changes in national and provincial veterinary structures, lack of funding and trained personnel, and disease prioritization have resulted in failure to control the disease in South Africa. With the growth in the private game industry and translocations associated with conservation programs, there were new challenges in detecting and managing BTB in species for which there were no available diagnostic tests. In addition, the previous eradication schemes for BTB and brucellosis did not include wildlife since there was a misperception that these species were not important in disease maintenance.
Recent outbreaks of BTB in wildlife in multiple new locations around South Africa illustrate the importance of an integrated approach to control strategies (Figure 1). It is estimated that between 70,000 and 200,000 wild animals are moved annually in South Africa. This represents a significant potential risk for moving diseases. Examples have been documented for BTB spread associated with translocation of wildlife. One game reserve with genetically valuable African buffalo was found to have a high prevalence of BTB which was traced back to introduction of untested greater kudu, blue wildebeest and impala onto the farm. This has resulted in quarantine and costly testing of the current stock.
Discovery of M. bovis on a property results in quarantine, resulting in loss of income from animal products and ecotourism, inability to move animals for conservation or breeding programs, and stigmatization. Without accurate ante-mortem diagnostic tests, these restrictions become permanent, effectively isolating the wildlife population. In addition, livestock that border areas with infected wildlife are at risk of spill-back. This has already occurred in rural cattle that border the Kruger National Park.
Recent confirmation of M. bovis infection in free-ranging white and black rhinoceros in Kruger National Park has led to a halt in translocations. Inability to move animals to other locations has confounded anti-poaching efforts and conservation programs.
Development of new diagnostic techniques for detection of BTB in wildlife and their implementation in disease surveillance programs are critical to mitigate the spread of diseases to new locations and populations, especially those that are fragmented and contain endangered species. Research, communication between wildlife, veterinary, regulatory and public health professionals, and implementation of a One Health approach is essential to stemming the re-emergence of this disease.
By: Michele A. Miller, DVM, MS, MPH, PhD
NRF South African Research Chair in Animal TB, Stellenbosch University, South Africa