Background: Zoonotic tuberculosis (zTB) accounts for 1.4% of the global tuberculosis burden, with the largest disease burden in low- and middle-income countries (LMICs). These populations have increased exposure to zTB due to livestock rearing practices and raw dairy consumption. This qualitative systematic literature review evaluates the quality of the literature that examines the association between human zTB in LMICs and frequent exposure to livestock and livestock products and summarizes current gaps in laboratory detection methods.
Methods: The Navigation Guide, a systematic review framework utilized to assess environmental health exposures, was used to conduct this literature review. Peer-reviewed research articles were selected and evaluated for risk of bias and quality of evidence. Only studies conducted in LMICs that mentioned livestock or livestock product exposure and had a confirmed diagnosis were eligible.
Results: Fifteen studies met the inclusion criteria. Reported prevalence of human zTB ranged from 0% to 28%, with cattle and raw dairy the primary exposures. All confirmed zTB cases were Mycobacterium bovis. Eight of the 15 studies included livestock sampling, predominantly cattle and reported prevalence of zTB between 0% and 23%. Laboratory methods used included nearly a dozen different culture methods and a variety of molecular methods, some of which are not appropriate for zTB.
Conclusions: This review revealed the need for appropriate and standardized laboratory diagnostic methods, and large prospective studies of at-risk populations to determine exposures that lead to an increased risk of tuberculosis conversion/infection to better understand the true burden of disease. Standardized, easy to implement laboratory diagnostics is an imperative focus for this scientific field to better identify the burden of zTB. Future studies pairing livestock and human subjects will allow better characterization of the high zTB transmission areas for targeted control and prevention programmes.
Keywords: Mycobacterium bovis; humans; livestock; ruminants; tuberculosis; zoonosis.
© 2020 The Authors. Zoonoses and Public Health published by Blackwell Verlag GmbH.
Conflict of interest statement
The views presented in this paper are those of the authors and do not necessarily reflect the views or policies of the George Washington University. The authors declare no competing financial interests or other source of conflict of interest.
Differences in primary sites of infection between zoonotic and human tuberculosis: results from a worldwide systematic review.PLoS Negl Trop Dis. 2013 Aug 29;7(8):e2399. doi: 10.1371/journal.pntd.0002399. eCollection 2013. PLoS Negl Trop Dis. 2013. PMID: 24009789 Free PMC article. Review.
Building a Multi-Institutional and Interdisciplinary Team to Develop a Zoonotic Tuberculosis Roadmap.Front Public Health. 2018 Jun 12;6:167. doi: 10.3389/fpubh.2018.00167. eCollection 2018. Front Public Health. 2018. PMID: 29951476 Free PMC article.
Epidemiology of Mycobacterium bovis and Mycobacterium tuberculosis in animals: Transmission dynamics and control challenges of zoonotic TB in Ethiopia.Prev Vet Med. 2018 Oct 1;158:1-17. doi: 10.1016/j.prevetmed.2018.06.012. Epub 2018 Jun 28. Prev Vet Med. 2018. PMID: 30220382 Review.
Molecular identification of Mycobacterium bovis and the importance of zoonotic tuberculosis in Mexican patients.Int J Tuberc Lung Dis. 2011 Oct;15(10):1409-14. doi: 10.5588/ijtld.10.0608. Int J Tuberc Lung Dis. 2011. PMID: 22283903
Human Mycobacterium bovis infection in the United Kingdom: Incidence, risks, control measures and review of the zoonotic aspects of bovine tuberculosis.Tuberculosis (Edinb). 2006 Mar;86(2):77-109. doi: 10.1016/j.tube.2005.05.002. Epub 2005 Oct 28. Tuberculosis (Edinb). 2006. PMID: 16257579 Review.
- Center for Food Security and Public Health (CSFPH) (2009). Bovine tuberculosis. Retrieved from http://www.cfsph.iastate.edu/Factsheets/pdfs/bovine_tuberculosis.pdf
- Centers for Disease Control and Prevention (CDC) (2016). Fact sheets: Tuberculin skin testing. Retrieved from https://www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm
- Cordova E., Gonzalo X., Boschi A., Lossa M., Robles M., Poggi S., & Ambroggi M. (2012). Human Mycobacterium bovis infection in Buenos Aires: Epidemiology, microbiology and clinical presentation. The International Journal of Tuberculosis and Lung Disease, 16(3), 415–417. 10.5588/ijtld.10.0605 - DOI - PubMed