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9 July 2019 AN INTERFERON GAMMA RELEASE ASSAY FOR THE DETECTION OF IMMUNE SENSITIZATION TO MYCOBACTERIUM BOVIS IN AFRICAN WILD DOGS (LYCAON PICTUS)
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Abstract

In South Africa, the largest proportion of the African wild dog (Lycaon pictus) population resides in regions where buffaloes have a high prevalence of Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB). Recent reports of deaths of wild dogs associated with bTB have raised concerns regarding the threat this disease might pose for this species. In order to understand the potential impact of the disease in wild dogs, diagnostic tools are required to identify infected individuals. The interferon gamma (IFN-γ) release assay (IGRA) is commonly used for tuberculosis (TB) screening of humans, cattle, and other species, and the aim of this study was to develop an IGRA for wild dogs to detect immune sensitization. Blood was collected from immobilized wild dogs from the Ann van Dyk Cheetah Centre (AvDCC; n=9) and Kruger National Park (KNP; n=31). Heparinized whole blood was incubated overnight in QuantiFERON®-TB Gold (QFT) blood collection tubes and with selected mitogens, after which the plasma fraction was harvested. Three canine IFN-γ enzymelinked immunosorbent assays (ELISAs) were compared for detection of wild dog IFN-γ in plasma and the R&D Quantikine canine IFN-γ ELISA was selected for measurement of M. bovis-specific IFN-γ release in plasma samples. An IGRA result was calculated as the concentration in plasma derived from the QFT TB Antigen tubes minus that in the QFT Nil tube. An IGRA cut-off value was calculated using the IGRA results of M. bovis-unexposed individuals from AvDCC. Using this cut-off value, 74% (23/31) of M. bovis-exposed KNP wild dogs were IGRA positive, indicating immune sensitization to TB antigens in these animals. Three M. bovis culture-positive wild dogs from KNP had IFN-γ concentrations between 758 and 1,445 pg/mL, supporting this interpretation. This warrants further investigation into the prevalence of M. bovis infection in the KNP population.

© Wildlife Disease Association 2019
Roxanne L. Higgitt, O. Louis van Schalkwyk, Lin-Mari deKlerk-Lorist, Peter E. Buss, Peter Caldwell, Leana Rossouw, Tebogo Manamela, Guy A. Hausler, Paul D. van Helden, Sven D. C. Parsons, and Michele A. Miller "AN INTERFERON GAMMA RELEASE ASSAY FOR THE DETECTION OF IMMUNE SENSITIZATION TO MYCOBACTERIUM BOVIS IN AFRICAN WILD DOGS (LYCAON PICTUS)," Journal of Wildlife Diseases 55(3), 529-536, (9 July 2019). https://doi.org/10.7589/2018-03-089
Received: 31 March 2018; Accepted: 3 October 2018; Published: 9 July 2019
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