Milken Institute School of Public Health Poster Presentations (Marvin Center & Video)

Title

The Occurrence of Zoonotic Tuberculosis among People with Livestock Exposure in Low- and Middle-Income Countries: A Systematic Review

Poster Number

44

Document Type

Poster

Status

Graduate Student - Masters

Abstract Category

Environmental and Occupational Health

Keywords

zoonotic tuberculosis, livestock, Mycobacterium bovis, TB, human

Publication Date

Spring 2018

Abstract

Zoonotic tuberculosis (zTB) makes up an estimated 1.4% of the global tuberculosis burden. Cases are largely underreported and misdiagnosed because the largest burden of disease is in low and middle income countries (LMICs). Populations in LMICs are at increased risk of zTB due to livestock rearing practices and raw dairy consumption. This systematic review of the literature investigates the risk of human zoonotic tuberculosis in LMICs based on exposure to livestock and livestock products.

Utilizing the Navigation Guide, the study question was identified, peer-reviewed literature databases (Scopus, PubMed, and Web of Science) were searched, and studies were selected and evaluated for risk of bias and quality of evidence. Fifteen studies in LMICs were included in the final evaluation that used laboratory diagnostics to determine the species of Mycobacterium. Overall there was probably low risk of bias and low quality of the evidence. Prevalence of zTB reported in the observational studies ranged from 0% to 28%, with cattle and raw dairy being the primary exposure. All confirmed cases of zTB in these studies were Mycobacterium bovis.

Four of six WHO regions were represented: Africa (n=9), the Americas (n=3), Southeast Asia (n=2), and the Eastern Mediterranean region (n=1). Several studies looking at pastoralist communities found low to zero prevalence of zTB in humans. Eight of the 15 studies included livestock sampling for zTB during a similar timeframe as human sampling, finding prevalence rates ranging from 0-23% in sampled livestock, which were predominantly cattle. One study found TB lesions in goats and camels at slaughter as well. There are several concerns with the body of evidence: variability and reliability of laboratory diagnostics, small sample sizes, differential risk of zTB based on livestock breed and production setting, and the need for global dairy pasteurization.

Large scale studies that pair livestock and human data are greatly needed to fill knowledge gaps. More emphasis must be placed on livestock TB surveillance and control programs and safe dairy consumption, such as pasteurization and boiling. Future paired studies will allow better characterization of the high zTB transmission areas for targeted control and prevention programs.

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The Occurrence of Zoonotic Tuberculosis among People with Livestock Exposure in Low- and Middle-Income Countries: A Systematic Review

Zoonotic tuberculosis (zTB) makes up an estimated 1.4% of the global tuberculosis burden. Cases are largely underreported and misdiagnosed because the largest burden of disease is in low and middle income countries (LMICs). Populations in LMICs are at increased risk of zTB due to livestock rearing practices and raw dairy consumption. This systematic review of the literature investigates the risk of human zoonotic tuberculosis in LMICs based on exposure to livestock and livestock products.

Utilizing the Navigation Guide, the study question was identified, peer-reviewed literature databases (Scopus, PubMed, and Web of Science) were searched, and studies were selected and evaluated for risk of bias and quality of evidence. Fifteen studies in LMICs were included in the final evaluation that used laboratory diagnostics to determine the species of Mycobacterium. Overall there was probably low risk of bias and low quality of the evidence. Prevalence of zTB reported in the observational studies ranged from 0% to 28%, with cattle and raw dairy being the primary exposure. All confirmed cases of zTB in these studies were Mycobacterium bovis.

Four of six WHO regions were represented: Africa (n=9), the Americas (n=3), Southeast Asia (n=2), and the Eastern Mediterranean region (n=1). Several studies looking at pastoralist communities found low to zero prevalence of zTB in humans. Eight of the 15 studies included livestock sampling for zTB during a similar timeframe as human sampling, finding prevalence rates ranging from 0-23% in sampled livestock, which were predominantly cattle. One study found TB lesions in goats and camels at slaughter as well. There are several concerns with the body of evidence: variability and reliability of laboratory diagnostics, small sample sizes, differential risk of zTB based on livestock breed and production setting, and the need for global dairy pasteurization.

Large scale studies that pair livestock and human data are greatly needed to fill knowledge gaps. More emphasis must be placed on livestock TB surveillance and control programs and safe dairy consumption, such as pasteurization and boiling. Future paired studies will allow better characterization of the high zTB transmission areas for targeted control and prevention programs.