aetiopathogenesis of tuberculosis

8/14/2019 Aetiopathogenesis of Tuberculosis

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TOWARDS ERADICATING

TUBERCULOSIS-AETIOPATHOGENESIS OF

TUBERCULOSIS-

Dr. A. O. Oluwasola

MBBS FWACP(lab. Med.) Msc. Epid.

Snr. Lecturer/Consultant Pathologist


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WHY THE NEED TO PURSUE TB

ERADICATION? The eradication of smallpox from the world in 1977 proved

the feasibility of infectious disease eradication About a third of world popn. is infected with TB

Yet the global epidemic is growing and becoming moredangerous

The breakdown in health services, the spread of HIV/AIDSand the emergence of multidrug-resistant TB arecontributing to the worseningimpact of this disease.

In 1993, the World Health Organization (WHO) declaredtuberculosis a global emergency!!!


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WHAT IS TUBERCULOSIS? 'Tuberculosis' is a chronic infectious disease Usually caused by the bacterium

Mycobacterium tuberculosis,

Most commonly affects the lungs (pulmonary TB) Up to a third affect other organs: CNS, UGS, Tubercu..losis

Tubercle. knob-like(L)

losis condition(GK)
http://www.tutorgig.com/ed/bacteriumhttp://www.tutorgig.com/ed/Mycobacterium_tuberculosishttp://www.tutorgig.com/ed/lunghttp://www.tutorgig.com/ed/lunghttp://www.tutorgig.com/ed/Mycobacterium_tuberculosishttp://www.tutorgig.com/ed/bacterium


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OTHER NAMES FOR THE

DISEASE ARE: 'TB' Koch`s disease 'Consumption' 'Wasting disease'

'White plague' 'Phthisis' (Gk word for consumption) and 'phthisis pulmonalis' 'Scrofula' (swollen neck glands) 'King's evil' 'Pott's disease' of the spine 'Tabes mesenterica' (TB of the abdomen)

'Lupus vulgaris' (the common wolf - TB of the skin) 'Prosector's wart', also a kind of TB of the skin, transmitted by contact

with contaminated cadavers to anatomists, pathologists, veterinarians,surgeons, butchers, etc.
http://www.tutorgig.com/ed/Scrofulahttp://www.tutorgig.com/ed/Pott%27s_diseasehttp://www.tutorgig.com/ed/Lupus_%28disambiguation%29http://www.tutorgig.com/ed/Prosector%27s_warthttp://www.tutorgig.com/ed/anatomisthttp://www.tutorgig.com/ed/pathologisthttp://www.tutorgig.com/ed/veterinarianhttp://www.tutorgig.com/ed/surgeonhttp://www.tutorgig.com/ed/butcherhttp://www.tutorgig.com/ed/butcherhttp://www.tutorgig.com/ed/surgeonhttp://www.tutorgig.com/ed/veterinarianhttp://www.tutorgig.com/ed/pathologisthttp://www.tutorgig.com/ed/anatomisthttp://www.tutorgig.com/ed/Prosector%27s_warthttp://www.tutorgig.com/ed/Prosector%27s_warthttp://www.tutorgig.com/ed/Lupus_%28disambiguation%29http://www.tutorgig.com/ed/Lupus_%28disambiguation%29http://www.tutorgig.com/ed/Pott%27s_diseasehttp://www.tutorgig.com/ed/Pott%27s_diseasehttp://www.tutorgig.com/ed/Scrofula


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AETIOLOGY Tuberculosis, is caused by bacteria belonging to

the Mycobacterium tuberculosis complex. Belong the family Mycobacteriaceae and the order

Actinomycetales. The most frequent and important agent of humandisease is M. tuberculosis.

The classical Myc. tb. complex also includes: M. bovis,

M. africanum & M. microtii.


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CHARACTERISTICS OF

MYCOBACTERIA M. tuberculosis is a rod-shaped, non-spore-forming, thin

aerobic bacterium measuring about 0.5 um by 3 um. Acid-fast bacilli (AFB). -ZN stain; due to cell wall lipids

Lipids (e.g., mycolic acids) are linked to underlyingarabinogalactan and peptidoglycan. antbt. ineff. Lipoarabinomannan(LAM), -pathogen-host interaction &

facilitates the survival ofM. tuberculosis withinmacrophages.

The complete genome sequence comprises about 4000genes -antigenic variations\point mutations /MDR


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EPID EMIOL OGY 1.7 billion individuals worldwide, 90% -developing

countries 8 to 10 million new cases and 1.7 million deaths annually.

2nd

leading infectious cause of death in the world. Infection with HIV makes people susceptible to rapidly

progressive tuberculosis; Over 50 million people are infected with both HIV and M.

tuberculosis.

Without greater control efforts, the annual incidentcases of tuberculosis globally may increase by 40%between now and 2020.


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TB CASE NOTIFICATION RATE


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Tuberculosis flourishes wherever there is

poverty, crowding, and chronic debilitating

illness. In the United States, tuberculosis is mainly

a disease of the elderly, the urban poor,

and people with AIDS.

Certain medical conditions increase risk that

TB infection will progress to TB disease

EPIDEM IOLOGY CTD


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Conditions That Increase the Risk ofProgression to TB Disease

HIV infection

Substance abuse

Recent infectionChest radiograph findings suggestive of

previous TB

Diabetes mellitus

Silicosis

Prolonged corticosteriod therapy

Other immunosuppressive therapy


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Conditions That Increase the Risk ofProgression to TB Disease (cont.)

Cancer of the head and neck

Hematologic and reticuloendothelial diseases

End-stage renal disease

Intestinal bypass or gastrectomy

Chronic malabsorption syndromes

Low body weight (10% or more below the idea


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Epidemiologic concept of infection/disease The chain of infection-

RESERVOIR of infection is humans with active

tuberculosis. TRANSMISSION mainlyby droplet nuclei, which

are aerosolized by coughing, sneezing, or speaking. Other routes:- skin & placenta, are uncommon.

SUSCEPTIBLE HOST: - Acquired & genetic factors.

FROM EXPOSU RE TOINF ECTIO N


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IMPORTANT DETERMINANTS OF

TRANSMISSION:-Mainly exogenous:The probability of contact with a case of

tuberculosis,The intimacy and duration of that

contact,The degree of infectiousness of the

case,The shared environment of the contact


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SPREAD BY DROPLET NUCLEI


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FROM INFECTION TODIS EASE Mainly endogenous Balance between bactericidal

activity/virulence The individual's innate susceptibility to

disease

age, sex, genetic factors- #2q35 Level of function of cell-mediated immunity-

acquired or congenital immunodeficiency


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PATH OGENES IS

Following inhalation ~10% alveoli

Virulence genes:- katG, rpov, erp

Number of invading bacilliResistance/susceptibility genes:-

NRAMP1polymorphism

DTH


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SEQUENCE OF EVENTS IN FIRST 3

WEEKS AFTER INFECTION


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EVENTS OCCURRING AFTER 3

WEEKS OF EXPOSURE


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Thin section transmission electron

micrograph ofMycobacterium

tuberculosis


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MYCOBACTERIA DEMONSTRABLE

WITH ACID-FAST STAINS


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A TUBERCULOUS GRANULOMA


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HYPERSENSITIVITY REACTION


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THE NATURAL HISTORY AND

SPECTRUM OF TUBERCULOSIS


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GHON COMPLEX


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SECONDARY PULMONARY

TUBERCULOSIS


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MILIARY TUBERCULOSIS OF

THE SPLEEN


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COMPLICATIONS OF

TUBERCULOSIS

PRIMARY TB2. Reactive pleural effusion

3. Tuberculous pleurisy

4. Bronchial occlusion

5. Bronchopneumonia

6. Pericarditis

7. Laryngitis

8. Pulmonary collapse

9. Body wasting

10. Localised TB in anotherorgan

11. Miliary tuberculosis

POSTPRIMARY TB2. Reactive pleural effusion

3. Pleural tuberculosis

4. Cavitation- hmge; tb brpn;pnthorax; aspergilloma

5. Bronchiectasis

6. Progressive pulm. fibrosis

7. Destroyed lung synd.

8. Percarditis

9. Miliary TB10. Amyloidosis

11. ARDS


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PROSPECTS FOR ERADICATION

1. PREPATHOGENESIS ?Ignorance

?Poverty

?Specific protection

3. PERIOD OF PATHOGENESIS

?Predisposing diseases

?Cytokines/immunotherapy/host immunity

?Genes/genotherapy

4. ?OTHER LEVELS/FACTORS


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THANK YOU FOR YOUR ATTENTION

aetiopathogenesis of tuberculosis

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