Aetiopathogenesis of Tuberculosis
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Transcript of 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