Review of Diagnostic Tests for Detection of Mycobacterium bovis Infection in South African Wildlife

Abstract

Wildlife tuberculosis is a major economic and conservation concern globally. Bovine tuberculosis (bTB), caused by Mycobacterium bovis (M. bovis), is the most common form of wildlife tuberculosis. In South Africa, to date, M. bovis infection has been detected in 24 mammalian wildlife species. The identification of M. bovis infection in wildlife species is essential to limit the spread and to control the disease in these populations, sympatric wildlife species and neighboring livestock. The detection of M. bovis-infected individuals is challenging as only severely diseased animals show clinical disease manifestations and diagnostic tools to identify infection are limited. The emergence of novel reagents and technologies to identify M. bovis infection in wildlife species are instrumental in improving the diagnosis and control of bTB. This review provides an update on the diagnostic tools to detect M. bovis infection in South African wildlife but may be a useful guide for other wildlife species.

Detection of Mycobacterium tuberculosis complex DNA in oronasal swabs from infected African buffaloes (Syncerus caffer)

“…These are typically based on cytokine release in plasma from whole blood stimulated with the TB antigens, early secretory antigenic target protein 6 (ESAT-6) and culture filtrate protein 10 (CFP-10), or bovine and avian tuberculins. The bovine interferon-gamma (IFN-γ) release assay (IGRA) and IFN-γ-induced protein 10 (IP-10) assay (IPRA) have been adapted from assays developed for cattle for use in buffaloes 2 , 8 . However, confirmation of M. bovis infection requires direct detection of the organism, which is usually based on post-mortem mycobacterial culture and genetic speciation of mycobacterial isolates from collected tissue samples 9 ; however, conventional mycobacterial culture methods are time-consuming, taking up to 56 days before results are available, and have limited sensitivity 2 , 10 .…”

Epidemiology ofMycobacterium bovisinfection in free-ranging rhinoceros in Kruger National Park, South Africa

“…A later study showed spread of M. bovis infection to African lions ( n = 70) sampled in 2012/2013 in the same areas of KNP, with an overall infection prevalence of 44% ( 32 ). Such extensive infection is increasingly observed in additional species in KNP, including warthogs ( 33 ), African wild dogs ( Lycaon pictus ) ( 23 ), and African elephants ( 34 ), with cases identified in more than 15 species in the park, to date ( 12 ). Taken together, these findings suggest that spillover of bTB is not a new occurrence and support the need for ongoing bTB surveillance across species to continuously assess disease risk and conservation impact, and to better understand transmission within and from the multihost system in KNP.…”

“…Historically, M. bovis is believed to have originated from infected cattle adjacent to the park boundaries in the 1960s and 1980s, but was not detected until the 1990s in infected buffalo herds ( 11 ). Since then, 15 additional wildlife species in KNP have been documented with infection ( 12 ), including rhinoceros, in which infection was confirmed using mycobacterial culture and M. bovis species confirmation ( 3 – 6 ).…”

“…The epidemiology of bTB in a complex system that contains multiple hosts with varying susceptibility results in an array of opportunities for infection spread. Black and white rhinoceros in KNP share environmental resources (including browse/grazing, and water sources) with potentially M. bovis –infected African buffaloes ( 8 – 10 ), greater kudu ( Tragelaphus strepsiceros ) ( 13 , 14 ), warthogs ( Phacochoerus africanus ) ( 15 ), and other species ( 12 ). A recent review of potential scenarios for interspecies transmission has suggested that rhinoceros may become infected with M. bovis in ecosystems containing other infected hosts ( 1 ).…”

“…It is therefore critical to be able to assess infection status in these populations. Recent advances in the development of diagnostic tests ( 12 , 25 ) for M. bovis infection in wildlife beyond conventional mycobacterial culture and M. bovis species confirmation has allowed for antemortem testing. The QuantiFERON TB Gold In-Tube Plus (QFT) (Qiagen)–interferon gamma release assay (QFT–IGRA) was recently validated for use in white rhinoceros ( 4 ), and has been used for testing KNP rhinoceros for M. bovis infection.…”