Epidemiology of tuberculosis

Dr. Shubhangi Kshirsagar
Assistant professor
Department of Swasthavritta & Yoga

 Tuberculosis is a specific infectious disease caused by
M. tuberculosis.
 The disease primarily affects lungs and causes pulmonary
tuberculosis.
 It can also affect intestine, meninges, bones and joints,
lymph glands, skin and other tissues of the body.
 The disease is usually chronic with varying clinical
manifestations.
 The disease also affects animals like cattle; this is known as
"bovine tuberculosis", which may sometimes be
communicated to man.
 Pulmonary tuberculosis, the most important form of
tuberculosis which affects man.
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Agent factors
a. Agent - Tuberculosis (TB) is a disease caused
by bacteria called Mycobacterium
tuberculosis.
b. Communicability
 Patients are infective as long as they remain
untreated.
 Effective anti-microbial treatment reduces
infectivity by 90 per cent within 48 hours.
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c. Source of infection
There are two sources of infection –
1. Human source
 Most common source of infection
 Human case whose sputum is positive for tubercle bacilli
and who has either received no treatment or has not been
treated fully.
 One infectious case of pulmonary TB contracts 10-15
persons
 There are two types of tuberculi bacilli in human
a. Slow multipliers – source of persister or dormant bacilli.
b. Rapid multipliers
2. Bovine source – infected milk
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Host factors
1. Age
 Tuberculosis affects all ages.
 In India,
2 % in the 0-14 years age group
20 % in 15-24 years age group
 In developed countries, it is more common in the elderly.
2. Sex - More prevalent in males than in females.
3. Heredity – It is not a hereditary disease
4. Nutrition – Malnutrition predispose to tuberculosis.
5 .Immunity – Man has no in hereditary immunity against TB
It is acquired as a result of natural infection or BCG
vaccination.
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Social factors
 Tuberculosis is a social disease with medical aspects.
 The social factors include many non-medical factors such
as -
• Poor quality of life
• Poor housing
• Overcrowding
• Population explosion
• Under-nutrition
• Lack of awareness of causes of illness
• Smoking
• Alcohol abuse
• Lack of education
• Large families
• Early marriages
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 All these factors are interrelated and contribute to the
occurrence and spread of tuberculosis.
 In fact, tuberculosis began to decline in the western world
long before the advent of chemotherapeutic drugs.
 This has been attributed to improvements in the quality of
life.
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Mode of transmission
 Tuberculosis is transmitted mainly by droplet infection
and droplet nuclei generated by sputum-positive patients with
pulmonary tuberculosis.
 Coughing generates the largest number of droplets of all sizes.
 The frequency and vigour of cough and the ventilation
of the environment influence transmission of infection.
 Tuberculosis is not transmitted by fomites, such as dishes and
other articles used by the patients.
 Sterilization of these articles is therefore of little or no value.
 Patients with extra-pulmonary tuberculosis or smear-negative
tuberculosis constitute a minimal hazard for transmission of
infection.
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Incubation period
 3 to 6 weeks.
 The development of disease depends upon the
closeness of contact, extent of the disease and sputum
positivity of the source case (dose of infection) and
host parasite relationship.
 Thus the incubation period may be weeks, months
or years.
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Clinical features
 Productive cough
 Haemoptysis
 Fever
 Weight loss
 Night sweat
 Fatigue
 Loss of appetite
 Lymph node swelling
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Control measures
 The control measures consist of –
1. Curative component
a. Case finding
i. Sputum smear exam by direct microscopy
ii. Radiography
iii. Sputum culture
b. Treatment
2. Preventive component - BCG vaccination
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Case finding tools
1. Sputum smear exam by direct microscopy
 Collection of sputum samples
2. Radiography
 Useful in diagnosis of smear negative TB
 TB in children
3. Sputum culture
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Day 1 Sample 1 On the spot sample under supervision
Day 2 Sample 2 Patient brings an early morning sample

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Directly observed treatment, Short
Course Chemotherapy (DOTS)
 It ensures cure by providing the most effective medicine and
confirming that it is taken.
 During intensive phase of treatment a health worker or
other trained person watches as the patient swallows the
drug in his presence.
 During continuation phase, the patient is issued
medicine for one week in a multiblister combipack, of which
the first dose is swallowed by the patient in the presence of
health worker or trained person. The consumption of
medicine in the continuation phase is also checked by
return of empty multiblister combipack, when the patient
comes to collect medicine for the next week.
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Two – phase chemotherapy
1. Intensive phase
 Short duration
 Early in course of treatment
 Lasting 1-3months
 3/> drugs
 Kills bacilli
2. Continuation phase
 6-9months
 Sterilization of smaller no. of dormant or persisting
bacteria
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Anti-tuberculosis drugs
 The currently used drugs may be classified into
two groups-
1. Bactericidal drugs – kill the bacilli in vio.
2. Bacteriostatic - inhibit the multiplication of the
bacilli and lead to their destruction by the
immune mechanism of the host.
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Anti-tuberculosis drugs
First line drugs
a. Bactericidal drugs
• Rifampicin(R)
• Isoniazid(INH)
• Streptomycin (S)
• Pyrazinamide(Z)
b. Bacteriostatic drugs
• Ethambutaol
Second line drugs
a. Bacteriostatic drugs
• Ethambutol
• Fluoroquinolones
• Ethionamide
• Capreomycin
• Kanamycin & Amikacin
• Cycloserine
• Thioacetazone
• Macrolides
• Bedaquilline (BDQ)
• Delamanid (DLM)
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Daily dose regimen
Type of TB Treatment regimen
Intensive
phase
Continuation
phase
New (2) HRZE (4) HRE
Previously
treated
(2) HRZES +
(1) HRZE
(5) HRE
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Fixed dose combination for adults
Weight
category
Type of
case
Number of tablets to be
consumed
Inj.
Steptomycin
Intensive
phase
Continuation
phase
HRZE HRE
75/150/400/275
mg per tab
75/150/275
mg per tab
gm
25-39kg New &
previo
usly
treated
2 2 0.5
40-54kg 3 3 0.75
55-69kg 4 4 1
>75kg 5 5 1
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Fixed dose combination for paediatric
Weight
category
Number of tablets to be consumed Inj.
Steptomycin
Intensive phase Continuation
phase
mg
HRE E HRE
50/75/150
mg per tab
100 50/175/100
mg per tab
4-7kg 1 1 1 100
8-11kg 2 2 2 150
12-15kg 3 3 3 200
16-24kg 4 4 4 300
25-29kg 3+1 A* 3 3+1 A* 400
30-39kg 2+2 A* 2 2+2 A* 500
A* - Adult FDC
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BCG Vaccination
1. Aim – To induce a benign, artificial primary infection
which will stimulate an acquired resistance to possible
subsequent infection with virulent tubercle bacilli.
2. Vaccine –
 BCG is the only widely used live bacterial vaccine.
 It consists of living bacteria derived from an attenuated
bovine strain of tubercle bacilli..
 The WHO has recommended, the "Danish 1331" strain for
the production of BCG vaccine.
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3. Type of vaccine –
There are two types of BCG vaccine -
a. Liquid (fresh) vaccine
b. Freeze-dried vaccine.
Freeze-dried vaccine is a more stable preparation and
used widely.
4. Dosage
 0.1 mg in 0.1 ml volume
 Dose to newborn aged below 4 weeks is 0.05 ml.
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5. Administration –
Intradermally using a "Tuberculin" syringe (Omega
microstat syringe fitted with a 1 cm steel 26 gauge
intradermal needle).
6. Age -
At birth (for institutional deliveries) or at 6 weeks of age
simultaneously with other immunizing agents.
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7. Phenomena after vaccination -
Normal reaction -
 Two to three weeks after a correct intradermal injection of
a potent vaccine, a papule develops at the site of
vaccination.
 It increases slowly in size and reaches a diameter of about
4 to 8 mm in about 5 weeks.
 It then subsides or breaks into a shallow ulcer, rarely open,
but usually seen covered with a
crust.
 Healing occurs spontaneously within 6 to 12 weeks
leaving a permanent, tiny, round scar, typically 4-8 mm in
diameter.
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8. Complications
 Prolonged severe ulceration at the site of
vaccination
 Suppurative lymphadenitis
 Osteomyelitis
 Disseminated BCG infection and death.
9. Protective value - from 15 to 20 years.
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Thank You !
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