Animal-to-human transmission of Mycobacterium tuberculosis


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GRF 2nd One Health Summit 2013: Presentation by Erin Passmore, University of New South Wales, Australia

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  • TB caused by M. Tuberculosis mainly effects humans but can also effect animals.In this presentation I will give 4 reasons why I think TB is important from a One Health perspective.
  • TB is primarily a human disease, but it also affects animals.Estimated that one third of the human population has latent TB infection.Prevalence of infection in animals is unknown, but for example estimated 5-10% Asian elephants in United States infected.TB can be transmitted between humans, from humans to animals, between animals, and from animals to humans. The capacity for MTB to be transmitted between species creates an interconnected network for disease transmission.
  • TB also illustrates how the environment can effect health. In humans, environmental factors play a big role in TB transmission – living crowded, poorly ventilated environments is a key contributor to the spread of TBIt is likely that the same applies to animals. Settings such as zoos and animal facilities – where animals are potentially housed out of direct sunlight, in close contact with other animals and humans – may create an ideal setting for TB transmission.
  • The second reason TB is important from a one health perspective is that humans play a significant role in disease transmission. TB is a reverse zoonosis – it is predominantly a human disease, that is sometimes transmitted to animals via close contact with humans.This challenges us to recognise the impact that humans have on animal health – to see humans as a source of disease for animals, rather than as ‘victims’ of a disease that is spread from animals to humans.
  • Michael Manfredo in his presentation yesterday talked about how we tend to neglect the human factors that contribute to zoonotic disease transmission.There are also a range of human activities that may increase opportunities for interspecies transmission of TB.Inadequate control of TB in some developing countries means there are many people with highly infectious TB, which may spread to both humans and animals.Currently mainly an issue for animals in captivity. But in the context of human population growth and destruction of animal habitats, TB in free-living animals may be a future One Health challenge.
  • The third reason TB is important from a One Health perspective is that there is substantial uncertainty about how to manage the risk of animal to human transmission.There are a diverse range of opinions about how to appropriately respond to an animal with TB – often the decision is made to euthanase the animal, as a precaution to protect human health, however not everyone believes this is justified. For example, in France in 2012, 2 elephants at Lyon Zoo were found to have TB. The local government decided the animals should be euthanased, as they posed a risk to human health. There was substantial community backlash – protesters didn’t want the animals to be killed. The highest profile objector was Brigitte Bardot, who threatened to leave France if the animals were killed. Eventually the French government overturned the local government’s decision, and ruled that the animals should be isolated and treated. As One Health professionals, we have an important role to play in this type of decision making – we have capacity to conduct research and assess risks about One Health issues, and can provide evidence-based guidance about control of zoonotic diseases.
  • TB demonstrates the importance of collaboration for disease control. Human, animal and environmental health experts need to work together to control zoonotic transmission of TB. At the moment, we don’t really know the scale of the problem of zoonotic transmission of TB, or how to best control it. Collaboration is needed to develop the capacity of all countries tor conduct surveillance, early detection and respond appropriately to disease outbreaks. At the moment, I think the priorities are:To develop international and protocols for surveillance and outbreak responses to zoonotic TB eventsTo develop guidance for risk assessment – to ensure that our response to an animal with TB is proportionate to the risk
  • To conclude, I hope I have demonstrated that TB is an important One Health challenge, and shown the importance of collaboration for disease control. Any questions?
  • Animal-to-human transmission of Mycobacterium tuberculosis

    1. 1. Zoonotic transmission of tuberculosis – the importance of a One Health approach Erin Passmore1 and Mark Ferson1,2 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
    2. 2. What is tuberculosis (TB)? • Caused by Mycobacterium tuberculosis complex: –M. tuberculosis (humans) –M. bovis (animals) –M. africanum –M. microti –M. canetti
    3. 3. TB in humans • Transmitted through prolonged close contact. • Bacteria are aerosolised when a person with active TB disease coughs, talks, laughs or sneezes • Most infections are asymptomatic (latent TB infection), 10% eventually progress to active disease. • Symptoms: Coughing, weight loss, fever, night sweats • If untreated, fatal in 50% of cases.
    4. 4. Why is TB important for One Health?
    5. 5. 1. Interconnectedness of human, animal and environmental health
    6. 6. 1. Interconnectedness of human, animal and environmental health • Humans: Living conditions contribute to TB transmission in humans (crowding, ventilation) • Animals: Close humananimal and animalanimal contact in zoos/animal facilities may facilitate transmission
    7. 7. 2. Humans as a source of infection in animals • Mainly transmitted from humans to animals – a ‘reverse zoonosis’ – M. tuberculosis does not have a natural nonhuman host or reservoir – Does not occur in free-living animals that have not had contact with humans • Humans as a source of disease in animals, rather than ‘victims’ of a disease transmitted from animals
    8. 8. 2. Humans as a source of infection in animals • Increasing opportunities for animal-human interactions where TB transmission can take place: – Inadequate TB control in many countries – Human population growth – Animal habitat destruction
    9. 9. 3. Dealing with uncertainty "Once these animals have been exposed to M. tuberculosis…they should never be allowed to be around the public again.” Patrick Ryan, Los Angeles Dept of Health
    10. 10. 4. Collaboration for effective tuberculosis control • Interdisciplinary collaboration is essential for controlling zoonotic transmission of TB. • Develop capacity of all countries for: – surveillance – early detection – appropriate responses to outbreaks • Next steps: – International and national protocols for surveillance and outbreak response – Risk assessment to ensure response is proportionate to level of risk
    11. 11. Thank you Contact: Erin Passmore