Zoonotic transmission of tuberculosis – the importance of a One Health approach
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GRF 2nd One Health Summit 2013: Presentation by Erin Passmore, University of New South Wales, Australia
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Zoonotic transmission of tuberculosis – the importance of a One Health approach
- 1. Animal-to-human transmission of Mycobacterium tuberculosis Erin Passmore1, Mark Ferson1,2, Siranda Torvaldsen1 1 School of Public Health and Community Medicine, University of New South Wales, Australia 2 Public Health Unit, South East Sydney Local Health District, New South Wales, Australia
- 4. 1. How often does animal-to-human transmission of M. tuberculosis occur? 2. Who is most at risk?
- 5. Transmission in animal facilities • Six articles described M. tuberculosis transmission in zoos/refuges • Two articles described M. tuberculosis transmission during necropsies • Index case: wild animals (e.g. elephant, rhino, chimpanzee) and domestic pets
- 6. How often does animal-tohuman transmission of M. tuberculosis occur?
- 7. • 8 outbreak investigations • Of 567 people screened (range 10-307): – Total 103 people with latent TB infection (range 12%-50%) – 2 people with active TB disease • Limitations – No proof that the people with latent TB infection were infected by the animal with TB
- 8. Question: How often does animal-tohuman transmission of M. tuberculosis occur? Answer: Rarely. But the research has many limitations.
- 9. Who is most at risk?
- 10. 1. Close contact with animals with TB • Two studies found increased risk of latent TB infection in staff who have direct physical contact with an animal with TB (e.g. trainers, handlers) • Consistent with human model of TB transmission • Long recognised that primate caretakers in zoo and laboratory settings at increased risk of M. tuberculosis infection
- 11. 2. Necropsy • Four studies identified an increased risk of latent TB infection in people who performed or attended necropsies of animals with TB • Consistent with increased risk of M. tuberculosis infection in human autopsy personnel • Linked to use of equipment that aerosolises infectious particles (e.g. saws)
- 12. 3. Aerosol-generating work activities • Two studies identified increased risk of latent TB infection in staff who cleaned areas used by infected animals • Hypothesis: animal waste containing M. tuberculosis aerosolised during cleaning (e.g. pressure hosing, sweeping) and inhaled • Aerosolisation implicated in outbreaks in human healthcare settings (e.g. medical waste)
- 13. Who is most at risk? • Three key activities associated with transmission: direct close contact, necropsies, aerosol-generating work activities • Indirect aerosolisation and environmental contamination may have a greater role in animal-to-human transmission than it does in human-to-human transmission • Need for higher quality studies
- 14. Thank you! Contact: Erin Passmore erin.passmore@student.unsw.edu.au
Editor's Notes
- In my first presentation, I described how TB is mainly a human disease, but can also be transmitted from humans to animals, between animals, and from animals to humans. In this presentation, I will look more closely about transmission of TB from animals to humans.
- Several times each year, there are reports in the media of zoo animals – usually elephants – having tuberculosis. For example, this year an elephant at Oregon Zoo was diagnosed with TB, and in the last few years there has been substantial media coverage around an elephant and a chimpanzee diagnosed with TB at Taronga Zoo in Sydney, 2 elephants at Lyon Zoo in France, and many others.Every time a new case is reported, it raises important questions about whether an animal with TB poses a risk to human health.
- Work in this area has focussed on two questions:How often do animals transmit TB to humans?What activities put people at risk?To answer these questions, I did a comprehensive literature review searching for any reports of animal to human transmission of TB – including searching academic databases, google and asking experts.As mentioned in my first presentation, there are five mycobacteria that cause TB, but my work has focussed on Mycobacterium tuberculosis, which causes TB in humans.
- I’ve found eight reports of animal to human transmission of TB – 6 articles describing transmission at zoos and refuges, and two describing transmission at necropsy.The animal “index” cases that prompted the investigations were wild animals (such as elephants, rhinos, chimpanzees) and domestic pets.The articles reported outcomes of screening humans who had contact with the animal with TB, such as zoo keepers and pet owners.
- The second question I sought to answer was “who is most at risk” of getting TB from an animal.Keeping in mind the limitations of the evidence, I identified three groups of people that seem to be most at risk.