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Tuberculosis: Basics

Rick SpeareAnton Breinl Centre

School of Public Health, Tropical Medicine and Rehabilitation Sciences

James Cook University

16 May 2011

Objectives

To provide background on TB to assist understanding of tuberculosis and control strategies

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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

TransmissionTransmission Droplet transmission is usual routeDroplet transmission is usual route MycobacteriumMycobacterium aerosolised into droplets aerosolised into droplets

(coughing, speaking, breathing)(coughing, speaking, breathing) Inhaled into alveoli of new hostInhaled into alveoli of new host Grows in alveoli (Ghon focus)Grows in alveoli (Ghon focus) Carried to bronchial lymph nodes (Ghon Carried to bronchial lymph nodes (Ghon

complex)complex) M. bovis M. bovis can also be spread in milk from can also be spread in milk from

infected bovine uddersinfected bovine udders44

Histology of the normal Histology of the normal alveolaealveolae

http://www.anatomy.dal.ca/Human%20Histology/Lab11/59ll4la.htmlhttp://www.anatomy.dal.ca/Human%20Histology/Lab11/59ll4la.html

Histopathology of TB granulomaHistopathology of TB granuloma

Risk of Transmission People in close contact with TB case have People in close contact with TB case have

highest risk of infection (clustered)highest risk of infection (clustered) Transmission can result from casual and brief Transmission can result from casual and brief

contact in highly endemic areascontact in highly endemic areas South African studies demonstrated this (Verver et al South African studies demonstrated this (Verver et al

2004)2004) Greater risk when number of bacteria are higherGreater risk when number of bacteria are higher Risk of transmission falls rapidly with treatmentRisk of transmission falls rapidly with treatment

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

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Pulmonary TB

Chronic cough Productive Haemoptysis Weight loss Night sweating

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Fatal pulmonary TB: Prisoner in Lilongwe, Malawi

Very severe consolidation, caseating necrosis and cavities

Another Malawaian patient with pulmonary TB and cavities

Consolidation Cavities

TB is a very destructive disease

Diagnose & treat early!

Death from TB

Respiratory failureRespiratory failure Severe haemoptysisSevere haemoptysis Systemic TB (miliary TB)Systemic TB (miliary TB) Meningeal TBMeningeal TB OtherOther

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Severe haemoptysis: patient often drowns in their own blood

Very destructive disease

Cavities due to patient coughing up necrotic lung

Fibrosis is common Damaged tissue can not be replaced Diagnose and treat early!

“Healed” Cavity

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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 …

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TB meningitis: infants & AIDS

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Osteomyelitis Arthritis

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Osteomyelitis of spine

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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

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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

Breaking Transmission Droplet transmission is usual routeDroplet transmission is usual route Points to break the transmission cycle:Points to break the transmission cycle:

Preventing viable Preventing viable MycobacteriumMycobacterium getting into getting into dropletsdroplets

Preventing droplets with Preventing droplets with MycobacteriumMycobacterium getting getting into the alveoli of a new hostinto the alveoli of a new host

Preventing Preventing MycobacteriumMycobacterium in alveoli from causing in alveoli from causing diseasedisease

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