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Tuberculosis: Basics

Rick Speare Anton Breinl Centre School of Public Health, Tropical Medicine and Rehabilitation Sciences James Cook University. Tuberculosis: Basics . 16 May 2011. Objectives. To provide background on TB to assist understanding of tuberculosis and control strategies. Tuberculosis.

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Tuberculosis: Basics

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  1. Rick Speare Anton Breinl Centre School of Public Health, Tropical Medicine and Rehabilitation Sciences James Cook University Tuberculosis: Basics 16 May 2011

  2. Objectives • To provide background on TB to assist understanding of tuberculosis and control strategies

  3. Tuberculosis • Due to the bacterium, Mycobacterium tuberculosis • Small % due to M. bovis • Pulmonary disease ± bloodstream spread to other organs • Bacilli are coughed up and inhaled by others • All ages can develop disease • Infection can be acquired in childhood, remain latent and emerge as immunity wanes

  4. Transmission • Droplet transmission is usual route • Mycobacterium aerosolised into droplets (coughing, speaking, breathing) • Inhaled into alveoli of new host • Grows in alveoli (Ghon focus) • Carried to bronchial lymph nodes (Ghon complex) • M. boviscan also be spread in milk from infected bovine udders

  5. Histology of the normal alveolae • http://www.anatomy.dal.ca/Human%20Histology/Lab11/59ll4la.html

  6. Histopathology of TB granuloma

  7. Risk of Transmission • People in close contact with TB case have highest risk of infection (clustered) • Transmission can result from casual and brief contact in highly endemic areas • South African studies demonstrated this (Verver et al 2004) • Greater risk when number of bacteria are higher • Risk of transmission falls rapidly with treatment

  8. http://www.health.vic.gov.au/ideas/diseases/tb_community

  9. Pulmonary TB • Chronic cough • Productive • Haemoptysis • Weight loss • Night sweating

  10. Fatal pulmonary TB: Prisoner in Lilongwe, Malawi

  11. Very severe consolidation, caseating necrosis and cavities

  12. Another Malawaian patient with pulmonary TB and cavities

  13. Consolidation • Cavities TB is a very destructive disease Diagnose & treat early!

  14. Death from TB • Respiratory failure • Severe haemoptysis • Systemic TB (miliary TB) • Meningeal TB • Other

  15. Severe haemoptysis: patient often drowns in their own blood

  16. Very destructive disease • Cavities due to patient coughing up necrotic lung • Fibrosis is common • Damaged tissue can not be replaced • Diagnose and treat early!

  17. “Healed” Cavity

  18. TB is mainly a pulmonary disease, but extra-pulmonary disease is common • Bacteraemia with seeding of multiple organs (miliary TB) • Localised infection in any other organ • Meningitis • Osteomyelitis • Arthritis • Lymph node infection • Other …

  19. TB meningitis: infants & AIDS

  20. Osteomyelitis Arthritis

  21. Osteomyelitis of spine

  22. Diagnosis of pulmonary TB • Detection of Mycobacterium tuberculosis in sputum • Culture of sputum • Smear of sputum • Acid fast bacilli (stained with acid fast stain) • PCR Pulmonary TB can not be diagnosed from a chest X-ray

  23. TB: Disease control • The focus in control of TB is only on the person spreading TB • Sputum positive case only (AFB+ = Sm+) • Other cases are of minor significance in control of TB Sometimes, clinical aims and TB control aims clash

  24. Breaking Transmission • Droplet transmission is usual route • Points to break the transmission cycle: • Preventing viable Mycobacterium getting into droplets • Preventing droplets with Mycobacterium getting into the alveoli of a new host • Preventing Mycobacterium in alveoli from causing disease

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