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Animal tuberculosis affects a wide range of domestic and wild animal species, including goats (Capra hircus). In South Africa, M ycobacterium tuberculosis complex (MTBC) testing and surveillance in domestic goats is not widely applied, potentially leading to under recognition of goats as a potential source of M. bovis spread to cattle as well as humans and wildlife. The aim of this study was to estimate diagnostic test performance for four assays and determine whether M. bovis infection was present in goats sharing communal pastures with M. bovis positive cattle in the Umkhanyakude district of Northern Zululand, KwaZulu Natal. In 2019, 137 M. bovis -exposed goats were screened for MTBC infection with four diagnostic tests: the in vivo single intradermal comparative cervical tuberculin test (SICCT), in vitro QuantiFERON®-TB Gold (QFT) bovine interferon-gamma release assay (IGRA), QFT bovine interferon gamma induced protein 10 (IP-10) release assay (IPRA), and nasal swabs tested with the Cepheid GeneXpert® MTB/RIF Ultra (GXU) assay for detection of MTBC DNA. A Bayesian latent class analysis was used to estimate MTBC prevalence and diagnostic test sensitivity and specificity. Among the 137 M. bovis -exposed goats, positive test results were identified in 15/136 (11.0%) goats by the SICCT; 4/128 (3.1%) goats by the IPRA; 2/128 (1.6%) goats by the IGRA; and 26/134 (19.4%) nasal swabs by the GXU. True prevalence was estimated by our model to be 1.1%, suggesting that goats in these communal herds are infected with MTBC at a low level. Estimated posterior means across the four evaluated assays ranged from 62.7% to 80.9% for diagnostic sensitivity and from 82.9% to 97.9% for diagnostic specificity, albeit estimates of the former (diagnostic sensitivity) were dependent on model assumptions. The application of a Bayesian latent class analysis and multiple ante-mortem test results may improve detection of MTBC, especially when prevalence is low. Our results provide a foundation for further investigation to confirm infection in communal goat herds and identify previously unrecognized sources of intra- and inter-species transmission of MTBC. • Positive MTBC test results were identified in goats using 4 MTBC diagnostic assays. • A Bayesian latent class analysis estimated MTBC prevalence and test performance. • Prevalence was estimated at 1.1%. • Diagnostic sensitivity ranged from 62.7% to 80.9%; specificity from 82.9% to 97.9%. • MTBC in communal goat herds presents risks to both human and animal health. [ABSTRACT FROM AUTHOR]

In South Africa, animal tuberculosis (TB) control programs predominantly focus on domestic cattle and African buffaloes (Syncerus caffer) despite increasing global reports of tuberculosis in goats (Capra hircus). Left undetected, Mycobacterium tuberculosis complex (MTBC) infected goats may hinder TB eradication efforts in cattle and increase zoonotic risk to humans. Since the publication of animal TB testing guidelines in 2018, prescribing the use of the tuberculin skin test (TST) for goats in South Africa by the Department of Agriculture, Land Reform, and Rural Development (DALRRD), there have been no published reports of any field application of the prescribed test criteria in goat herds. Therefore, this study aimed to evaluate the performance of these DALRRD guidelines using the single intradermal cervical tuberculin test (SICT) and the single intradermal comparative cervical tuberculin test (SICCT). Between October and December 2020, 495 goats from communal pastures of Kwa-Zulu Natal (KZN), where M. bovis infection has been identified in cattle and where cattle and goats cohabitate, were tested using the SICT and SICCT (M. bovis -exposed group). Additionally, 277 goats from a commercial Saanen dairy herd, with no history of M. bovis , were also tested (M. bovis -unexposed group). Estimated apparent prevalence of TST positive goats was determined based on published test interpretation criteria as described by DALRRD. When proportions of test-positive goats were compared between different DALRRD criteria, the ≥ 4 mm cut-off criterion for the SICCT resulted in the lowest proportion of positive results in the presumably uninfected group (1/277 positive in the unexposed group). The apparent prevalence of TB in the exposed group was estimated at 3.0% (95% CI: 1.7–4.9%), which is similar to previous reports of M. bovis prevalence in cattle from this area (6%). The detection of a significantly greater proportion of SICCT positive goats in the M. bovis -exposed group compared to the unexposed group suggests that MTBC infection is present in this population. Further investigations should be undertaken, in conjunction with confirmatory molecular tests, mycobacterial culture, and advanced pathogen sequencing to establish whether MTBC infection in domestic goats is a true under-recognized threat to the eradication of animal TB in South Africa. [ABSTRACT FROM AUTHOR]