ANTIBODY PREVALENCE TO AFRICAN SWINE FEVER VIRUS, MYCOBACTERIUM BOVIS, FOOT-AND-MOUTH DISEASE VIRUS, RIFT VALLEY FEVER VIRUS, INFLUENZA A VIRUS, AND BRUCELLA AND LEPTOSPIRA SPP. IN FREE-RANGING WARTHOG (PHACOCHOERUS AFRICANUS) POPULATIONS IN SOUTH AFRICA.

The warthog (Phacochoerus africanus) can be used as a model for investigating disease transmission at the human, wildlife, and livestock interface. An omnivore and scavenger, a warthog moves freely between natural ecotypes, farmland, and human communities and is susceptible to diseases of zoonotic, agricultural, and conservation concern. A retrospective study using 100 individual serum samples collected from May 1999 to August 2016 was performed to determine antibody prevalence to seven pathogens in warthogs from five locations in northeastern South Africa. Higher prevalence of antibodies to African swine fever virus and Mycobacterium bovis were detected in warthogs from the Greater Kruger National Park ecosystem in comparison to lower prevalence of antibodies to M. bovis and no antibodies to African swine fever virus in warthogs from uMhkuze Game Reserve. Low prevalence of antibodies to foot-and-mouth disease virus, Rift Valley fever virus, and influenza A virus was detected in all locations, and no antibodies against Brucella and Leptospira spp. were detected. No statistically significant difference in antibody prevalence was found between sexes for any disease. At the univariate analysis, M. bovis seropositivity was significantly different among age categories, with 49% (35/71) of adults found positive versus 29% (4/14) of juveniles and 9% (1/11) of sub-adults (Fisher's exact test, P=0.020), and between the sampling locations (Fisher's exact test, P=0.001). The multivariate model results indicated that juvenile warthogs had lower odds of testing positive to M. bovis antibodies than adults (juveniles' odds ratio [OR]=0.17, 95% confidence interval [CI]: 0.02-1.0), although this result was not statistically significant at the 5% level (P=0.052). For warthogs sampled at Satara Buffalo Camp, the odds (OR=0.22, 95% CI: 0.035-0.96) of being M. bovis antibody positive were significantly lower (P=0.043) than for warthogs sampled at Skukuza. Of particular interest in this study was the detection of warthogs seropositive for influenza A virus.

MYCOBACTERIUM BOVIS IN FREE-RANGING LIONS (PANTHERA LEO) - EVALUATION OF SEROLOGICAL AND TUBERCULIN SKIN TESTS FOR DETECTION OF INFECTION AND DISEASE.

Bovine tuberculosis (bTB), caused by Mycobacterium bovis infection, causes morbidity and mortality in free-ranging lions in bTB-endemic areas of South Africa. However, the only currently used diagnostic test is the tuberculin skin test (TST). This test is logistically challenging to perform because it requires immobilization of lions twice in a 72-hr period. Blood-based diagnostic tests, such as serological assays, have been previously reported for M. bovis detection in lion populations, and have the advantage of only requiring a single immobilization. In addition, serological assays can be used for retrospective testing. Therefore, the aim of this study was to test free-ranging lions with the STAT-PAKt (Chembio Diagnostics Systems, Medford, NY 11763, USA) and DPPt VetTB (Chembio Diagnostics Systems) serological assays and compare those results with the tuberculin skin test. The serological assays were also used to determine prevalence in bTB-endemic and uninfected lion populations. The results showed that the serological assays could distinguish between M. bovis culture-positive and -negative lions. In addition, antigen-specific humoral responses were present in lions that had clinical signs of bTB disease or were shedding M. bovis antemortem. Although the seroprevalence of M. bovis infection in Kruger National Park lions was similar to that obtained from antemortem mycobacterial culture (4.8 and 3.3%, respectively), it was less than that estimated by the TST (72%). These findings support the hypothesis that assays based on cell-mediated immune responses are more sensitive than serology is in detecting M. bovis infection in lions. However, serological assays can have a role in bTB disease detection in lions and are especially useful for retrospective studies.

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

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.