Estimates of the global and continental burden of animal tuberculosis in key livestock species worldwide: A meta-analysis study

Abstract

Zoonotic animal tuberculosis (TB) is a One Health paradigm infectious disease, caused by Mycobacterium tuberculosis complex bacteria, that affects different host species with varying levels of management. In most developed countries, official surveillance and control strategies support the longitudinal reporting of herd and/or animal prevalence. However, for under resourced countries without surveillance plans, this information may be obtained from cross-sectional studies only. The objective of this meta-analysis was to perform a worldwide estimate of the overall prevalence of animal TB in different livestock species whose importance in production systems varies according to the region of the world. The ISI's Web of Science and Google Scholar were searched combining keywords and related database-specific subject terms to identify relevant cohort or cross-sectional work published in this topic. A total of 443 articles were retrieved, screened, and a final set of 182 references included. Potential sources of variation were investigated using subgroup analyses and meta-regression. Prevalence estimates in five mammalian host groups were stratified according to host species, host characteristics, anatomical localization of lesions, sample size, geographical location, and diagnostic tests. The multivariable meta-regression analysis accounted for a range between 0% (farmed wild boar) and 68.71% (camelids) of the overall observed heterogeneity, indicating that the pondered predictors partially explain the observed variability. Differences in the overall prevalence of TB across hosts were small, with most groups showing values around 10%, except farmed wild boar (41%). The sample size emerged as an important moderator, with small size studies leading to the overestimation of prevalence. TB prevalence rates were very heterogeneous across continents and depended on the host, with lower values (below 10%) in Africa and Asia, while North America (33.6%, cattle), Europe (51%, goats), and South America (85.7%, pigs) exhibited higher rates, possibly related to greater densities of specific host groups managed on more intensive production systems. Stratification by diagnostic tests evidenced heterogeneous prevalence rates depending on the host group, possibly reflecting differences in test performance across different hosts. Results from this study highlight different TB burden scenarios, pinpointing host groups and diagnostics that should be prioritized in surveillance systems in different regions, thus providing policy-relevant information to catalyse TB control in settings with lower installed capacity and better resource allocation at the human-animal-environment interface.

The hard numbers of tuberculosis epidemiology in wildlife: A meta‐regression and systematic review

“…Considering the different moderators included in the three models, geographical location by country (3/3 models) and sample size (2/3) were the most statistically relevant predictors. The sample size may be a bias factor in small sample size studies, overestimating wildlife TB prevalence, as previously observed in the quantification of pooled TB prevalence in livestock (Ramos et al, 2020). The country variable proved to be an important moderator since specific wildlife hosts can be perceived as TB reservoirs in some countries (badgers in the UK, red deer and wild boar in the Iberian Peninsula and Central Europe), but spillover species in others.…”

Presence of Foodborne Bacteria in Wild Boar and Wild Boar Meat—A Literature Survey for the Period 2012–2022

“…These studies were performed both by serology ( Table 7 ) and by isolation or direct identification of mycobacteria in organs and tissues ( Table 8 ). The prevalence of MTC varies between countries and between regions/counties inside each nation (e.g., Spain), but also due to the investigated matrix and the diagnostic methods adopted [ 94 , 98 , 135 ]. In this context, some studies were performed to define the sensitivity of different diagnostic tools on sera and on organs and tissues [ 94 , 96 , 119 , 136 ].…”

Zoonotic Tuberculosis – The Changing Landscape

“…The animal TB burden is highly variable across countries and continents, with main variations according to predominant livestock systems. Although the available data may be biased due to different sampling strategies and diagnostic capacities, the highest animal prevalence is reported from the Americas and Europe ( Ramos et al, 2020 ).…”

“…However, zTB disease is largely underreported and, these wide ranges are indicative of major diagnostic challenges and poor public health surveillance and reporting structures in endemic countries. The highest numbers were reported from Africa (68,900) and South East Asia (43,400) ( Ramos et al, 2020 ) ( WHO, 2020a ). South-East Asia comprises almost 44% of the global TB burden ( WHO, 2020a ).…”