Unit 3 overview of tb disease
Download
1 / 24

Unit 3 Overview of TB Disease - PowerPoint PPT Presentation


  • 142 Views
  • Uploaded on

Unit 3 – Overview of TB Disease. Botswana National Tuberculosis Programme Manual Training for Medical Officers. Learning Objectives. At the end of this unit, participants will be able to: Describe the causes of TB Describe how TB is transmitted

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Unit 3 Overview of TB Disease' - lani


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Unit 3 overview of tb disease

Unit 3 – Overview of TB Disease

Botswana National Tuberculosis Programme Manual Training for Medical Officers


Learning objectives
Learning Objectives

At the end of this unit, participants will be able to:

  • Describe the causes of TB

  • Describe how TB is transmitted

  • Describe the difference between TB infection and TB disease

  • Identify high risk populations and high risk behaviours

  • Describe the pathogenesis of TB


What is tuberculosis
What is Tuberculosis?

TB is an illness caused by one of four (4) types of bacteria:

Mycobacterium tuberculosis (M. tuberculosis)

Mycobacterium bovis (M. bovis)

Mycobacterium africanum (M. africanum)

Mycobacterium microti (M. microti)

The majority of TB cases are caused by Mycobacterium tuberculosis

M. tuberculosis complex consists of all four bacteria


Characteristics of m tuberculosis 1
Characteristics of M. tuberculosis (1)

Slightly curved, rod shaped bacilli

0.2 - 0.5 microns in diameter and 2 - 4 microns in length

Acid fast - resists decolourisation with acid/alcohol

TB bacilli as seen under the microscope

Source: Kubica GP, CDC, 1979


Characteristics of m tuberculosis 2
Characteristics of M. tuberculosis (2)

Thick lipid cell wall

Multiplies every 18 - 24 hours

Can remain dormant for decades

Aerobic

Non-motile


Pathogenesis of tb
Pathogenesis of TB

Infection (implantation)

Multiplication

Dissemination (spread to other parts of the body)

Cell-mediated immune response (healing)

Reactivation


Definitions
Definitions

Alveoli

The small air sac at the end of the airways in the lungs

Macrophage

A type of white blood cell that eats bacteria or foreign organisms, found in the alveoli of the lungs

Granuloma

Nodular inflammatory lesions that contain compactly grouped mononuclear phagocytes (macrophages)

Tuberculous granulomas are often caseating (necrotic at their center) and contain Langerhans giant cells

AFB can often be seen on staining



Primary infection
Primary Infection

A person with primary infection may have:

No symptoms

Limited symptoms

Progressive symptoms


How tb is spread 1
How TB is Spread (1)

Person-to-person

Through the air by a person with TB disease of the lungs

Less frequently transmitted by ingestion of Mycobacterium bovis found in unpasteurised milk products

Rarely transmitted by inhalation of aerosolized infected fluids (e.g., TB abscess)


How tb is spread 2
How TB is Spread (2)

A person with infectious pulmonary TB (PTB) who coughs, sneezes, or speaks

Tiny particles of water (droplet nuclei) containing the TB bacteria enter the air and can remain suspended in the air for several hours

The bacteria can then be inhaled by others sharing the same air space

© ITECH, 2006

Source: CDC, 2001


Probability of transmission
Probability of Transmission

Environment in which exposure occurred

Infectiousness of person with TB

Immunologic status of exposed person

Duration of exposure

Virulence of the organism


Spread of tb to other parts of the body dissemination stage
Spread of TB to Other Parts of the Body (Dissemination Stage)

Pulmonary

Lymph nodes

Pleural Effusion

Miliary

Kidney

Spine

Meningitis

Source: CDC, 2001

© ITECH, 2006


Healing stage cell mediated immune response
Healing Stage: Stage)Cell-Mediated Immune Response

Process of halting the multiplication of the TB bacilli and preventing further spread

This same response causes the skin test to be positive

© University of Alabama at

Birmingham,

Department of Pathology

Granuloma


Latent infection
Latent Infection Stage)

Period of time during which the person experiences no symptoms but is still infected with the bacteria

The bacteria lives inside macrophages or within a granuloma where the bacteria remains dormant

A person with latent TB infection cannot spread the bacteria to other people


Reactivation of tb 1
Reactivation of TB (1) Stage)

Dormant bacteria can become active again

Escape granuloma and enter the airway

Source: CDC, 2001


Reactivation of tb 2
Reactivation of TB (2) Stage)

Latent infection can reactivate, causing active TB disease

Reactivation occurs when the immune system weakens and the TB bacteria multiplies

TB bacteria and dead cells in the airway will cause a person to cough

Higher proportion of smear-negative PTB in PLWHA


Question
Question Stage)

What is the difference between

TB infection and disease?


Infection
Infection Stage)

The bacteria lives inside a person without that person having any symptoms because the immune system is able to control the infection

Not all infected people develop TB disease

In HIV negative individuals, 10% lifetime risk of developing disease if TB infected

In HIV positive individuals, 10% ANNUAL risk of developing disease if TB infected


Disease
Disease Stage)

If the immune system cannot control the infection the bacteria multiply and cause disease

TB disease can develop soon after infection, many years after infection or it may never develop

What is one factor, besides HIV, that might increase the chance that TB infection progresses to disease?


Risk factors for progression from tb infection to tb disease 1
Risk Factors for Progression Stage)from TB Infection to TB Disease (1)

  • HIV/AIDS

  • Malnutrition

  • Recent TB infection

  • Extremes of age (children under 5 years of age and the very old)

  • Alcoholism and other substance abuse


Risk factors for progression from tb infection to tb disease 2
Risk Factors for Progression Stage)from TB Infection to TB Disease (2)

Silicosis of lung

Renal failure

Diabetes Mellitus

Lymphatic malignancies

Immunosuppressive medications and treatments including prolonged corticosteroid therapy

Gastrectomy

Source: Merck, 2005


Key points 1
Key Points (1) Stage)

Evidence of TB has been seen to be affecting humans for centuries

TB transmission occurs from persons with active pulmonary TB

TB droplets remain suspended in the air for hours

The bacteria can be killed by direct sunlight

Ventilation is important


Key points 2
Key Points (2) Stage)

When TB is first acquired, it causes primary infection

Persons with poor immunity, especially very young children and persons with AIDS, are more likely to have primary progressive disease

Latent infection-- period of time when person experiences no symptoms but is still infected with the bacteria


ad