EPIDEMIOLOGY OF TUBERCULOSIS

EPIDEMIOLOGY OF TUBERCULOSIS

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  EPIDEMIOLOGY OF TUBERCULOSIS DR MAHESWARIJAIKUMAR maheswarijaikumar2103@gmail.com
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  TUBERCULOSIS • Tuberculosis isa specific respiratory disease caused by m. tuberculosis. • The disease primarily affects lungs and causes pulmonary tuberculosis.
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  • It canalso affect intestine, meninges, bones and joints, lymph glands, skin and other tissues of the body. • The disease is usually chronic with varying clinical manifestations.
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  • The diseasealso affects animals like cattle (bovine tuberculosis) which may be sometimes communicated to man. • Pulmonary TB is the most important form of TB which affects man.
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  DISEASE BURDEN
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  NATURAL HISTORY OF TUBERCULOSIS
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  AGENT Mycobacterium tuberculosis
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  • M. tuberculosisis a facultative intracellular parasite.(readily ingested by phagocytes and is resistant to intracellular killing). • It is an acid fast, gram positive, rod shaped bacilli.
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  SOURCE OF INFECTION •There are two sources of infection-human and bovine.
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  • HUMAN SOURCE: The most common source of infection is the human case whose sputum is positive for tubercle bacilli, who has not received treatment or not treated fully.
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  COMMUNICABILITY • Patients areinfective as long as they remain untreated. • Effective antimicrobial treatment reduces infectivity by 90% within 48 hours.
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  HOST FACTORS
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  AGE & GENDER •Tuberculosis affects all ages. • TB is more prevalent in males than in females.
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  HEREDITY • Tuberculosis isnot a hereditary disease.
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  NUTRITION • Malnutrition (undernutrition) is widely believed to predispose TB.
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  IMMUNITY • Man hasno inherited immunity against TB. • It is acquired as a result of natural infection or BCG vaccination.
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  SOCIAL FACTORS • TBis social disease with medical aspects. It is considered to be a barometer of social welfare.
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  • The socialfactors include factors such as poor quality of life, poor housing, overcrowding, population explosion, under nutrition, lack of education, large families, lack of awareness of cause of illness.
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  • All theafore said factors are interrelated and contribute to the occurrence of TB.
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  MODE OF TRANSMISSION •TB is transmitted through droplet infection and droplet nuclei generated by sputum positive patients with pulmonary TB.
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  • To transmitinfection, the particles must be fresh enough to carry viable organism. • Coughing generates the largest number of droplets of all sizes.
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  • The frequencyand vigour of cough and the ventilation of the environment influence transmission of infection. • TB is not transmitted by fomites.
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  INCUBATION PERIOD • Rangesfrom 3 to 6 weeks, and thereafter the 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.
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  • Thus theincubation period in the real sense may extend to weeks, months or years.
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  CLINICAL MANIFESTATION
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  CONTROL OF TB
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  • The controlmeasures consists of : 1. CURATIVE COMPONENT. 2. PREVENTIVE COMPONENT.
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  • The mostpowerful tool in containing the disease is CASE FINDING AND TREATMENT.
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  CASE FINDING • Thefirst step in a tuberculosis control programme is early detection of sputum positive cases. • This must be done as an intensified ongoing programme.
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  CASE DEFINITION • WHOdefines a case as “a patient whose sputum is positive for tubercle bacilli, and such cases are the target of case finding.
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  SUSPECTS • All otherpossible sufferers from tuberculosis whose sputum is negative but show suggestive shadows in chest x-rays are reckoned as “suspects”.
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  CASE FINDING TOOLS 1.SPUTUM EXAMINATION. 2. RADIOGRAPHY. 3. SPUTUM CULTURE.
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  SPUTUM EXAMINATION • Sputumsmear examination is considered as the method of choice. • The tool is reliable and cheap.
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  • It enablesto discover epidemiologically most importance cases of pulmonary TB. • This group contributes most of the new cases to the “pool of infection” every year.
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  COLLECTION OF SPUTUM SAMPLES •Secretions build up in the airways overnight. • So an early morning sputum sample is more likely to contain TB bacilli.
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  In practice anout patient usually provides sputum sample as follows. DAY 1 SAMPLE 1 PROVIDES AN “ON THE SPOT” SAMPLE UNDER SUPERVISION WHEN PRESENTING TO THE HEALTH FACILITY. GIVE THE PATIENT A SPUTUM CONTAINER TO TAKE HOME FOR AN EARLY MORNING SAMPLE FO THE FOLLOWING MORNING.
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  DAY 2 SAMPLE2 PATIENT BRINGS AN EARLY MORNING SAMPLE.
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  ZIEHL-NEELSON ACID FASTSTAIN • ZN Stain detects the acid fast bacilli. • The ZN staining procedure is as follows.
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  • Fix thesmear on the side by passing the slide with the smear up about three times slowly through a flame. • It can also be done by covering the smear with alcohol and letting this evaporate.
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  • Cover withCarbolfuchsin, steam gently for 5 minutes over the direct flame( or for 20 min over a water bath). • Wash with deionized water.
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  • Decolourize in3 percent acid- alcohol (95% ethanol and 3% Hcl) until only a faint pink colour remains. • Wash with water.
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  • Counter stainfor 1 min with Loeffler’s methylene blue. • Wash with deionized water and let it dry.
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  SLIDE REPORTIING • Thenumber of bacilli seen in a smear reflects disease severity and patient infectivity. • Therefore it is important to record the number of bacilli seen on each smear.
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  NUMBER OF BACILLIRESULT REPORTED NO AFB per 100 oil immersions fields 0 1-9 AFB per 100 oil immersions fields Scanty (or number AFB seen)
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  NUMBER OF BACILLIRESULT REPORTED 10-99 AFB per 100 oil immersions fields + (1+) 1-10 AFB per 100 oil immersions fields ++ (2+)
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  NUMBER OF BACILLIRESULT REPORTED > 10 AFB per oil immersion field +++ (3+)
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  • Sputum smearmicroscopy for tubercle bacilli is positive when there are at least 10,000 organisms present per ml of sputum.
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  • One positivespecimen out of the two is enough to declare a patient smear positive. • Patients in whom both specimens are smear negative should be prescribed symptomatic treatment and broad spectrum antibiotic for 10-14 days.
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  • In suchcases antibiotics such as FLUOROQUINOLONES (ciprofloxacin, ofloxacin), rifampicin or streptomycin, which are active against TB should not be used.
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  FALSE POSITIVE RESULTS •A false positive result means that the sputum smear result is positive even though the patient does not really have sputum smear positive PTB.
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  FALSE NEGATIVE RESULT •A false negative result means that the sputum smear result is negative even though the patient does have sputum smear positive PTB.
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  FLUORESCENCE MICROSCOPY • Ismainly used in industrialized countries. It is performed with auramine stain. • This is a speedy examination and the field view of view is 5-10 times bigger.
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  LEDs • LIGHT EMITTINGDIODE FLUORESCENCE MICROSCOPY provide a much less expensive light source for fluorescence microscopy.
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  RADIOGRAPHY • Chest Xrays are useful for the diagnosis of smear negative PTB and TB in children. • It is essential in the diagnosis of miliary TB.
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  SPUTUM CULTURE • Cultureexamination of sputum is only second importance in case finding programme. • It takes 6 to 8 weeks for sputum culture.
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  DRUG SUSCEPTIBITY TESTING(DST) • DSTprovides a definitive diagnosis of drug-resistant TB.
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  • Phenotypic methodsinvolves culturing M.tubercolosis in the presence of anti TB drugs to detect the growth (indicating drug resistance) or inhibition of growth (indicating drug susceptabity)
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  • Genotypic methodtargets specific molecular mutations associated with resistance against individual drugs.
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  TUBERCULIN TEST • Tuberculintest was discovered by Von Pirquet in 1907. • A positive reaction to the test is generally accepted as evidence or past or present infection by M.tubercolosis.
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  • Tuberculin testis the only means of estimating the prevalence of infection in the population. • There are three main tests currently in use.
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  • They are: 1.MANTOUX TEST. 2. INTRADERMAL TEST. 3. HEAF & The TINE MULTIPLE PUNCTURE TEST.
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  TUBERCULIN • The testmaterial or antigen used for the test is called tuberculin. • There are two major antigens- the old tuberculin (OT) and the Purified Protein Derivative(PPD).
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  DOSAGE The dosages ofPPD in vogue are: 1. First Strength or 1 TU. 2. Intermediate Strength or 250 TU.
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  MANTOUX TEST • TheMantoux test is carried out by injecting intradermally on the flex or surface of the forearm 1 TU of PPD in 0.1ml. • The result is read after 72 hours (on the 3 day).
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  • Tuberculin reactionconsists of erythema and induration. • Since erythema is difficult to measure induration alone is measured using a transparent plastic ruler or callipers).
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  • Reaction exceeding10mm are considered “positive”. • Those less than 6 mm are considered negative. • Those between 6 and 9 mm are considered “doubtful”
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  TREATMENT
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  CHEMOTHERAPHY • THE FOLLOWING DRUGS ARE USEDIN THE MANAGEME NT PTB.
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  BACTERICIDAL DRUGS BACTERIOSTATIC DRUGS 1.Rifampicin(RMP). 1. Ethambutol. 2. INH. 2. Thiacetazone. 3. Strptomycin. 4. Pyrazinamide.
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  THE SECOND LINEDRUGS • Fluoroquinalones. • Ethionamide. • Capreomycin. • Kanamycin and Amikacin. • Cycloserine. • Macrolides.
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  DOSAGE FOR ADULTS WHORECOMMENDED TREATMENT REGIMEN - TUBERCULOSIS CATEGORY OF TREATMENT TYPE OF PATIENT REGIMEN Category I New sputum smear positive 2(HRZE)3, 4(HR)3 Seriously ill sputum smear negative Seriously ill extra- pulmonary
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  CATEGORY OF TREATMENT TYPE OF PATIENT REGIMEN CategoryII Sputum smear- positive relapse Sputum smear- positive failure Sputum smear- positive treatment after default 2(HRZES)3 1(HRZE)3 5(HRE)3
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  CATEGORY OF TREATMENT TYPE OF PATIENT REGIMEN CategoryIII New sputum smear-negative, not seriously ill New extra- pulmonary, not seriously ill 2(HRZ)3 4(HR)3
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  NOTE • H -Isoniaid (600mg) • R - Rifampicin (450mg) • Z - Pyrazinamide(1500mg) • E - Ethambutol(1200mg) • S - Streptomycin(750mg)
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  • Patient whoweight more than 60kg receive additional rifampicin 150mg. • patient more than 50years old receive Streptomycin 500mg.
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  DOSAGE FOR CHILDREN DRUGTHERAPHY per DOSE (THRICE A WEEK) ISONIAZID 10-15 mg/kg RIFAMPICIN 10 mg/kg
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  DRUG THERAPHY perDOSE (THRICE A WEEK) PYRAZINAMIDE 35 mg/kg STREPTOMYCIN 15 mg/kg ETHAMBUTOL 30 mg/kg
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  • ETHAMBUTOL shouldnot be given to children below 6 years of age.
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  DRUGS & SIDEEFFECTS REACTION DRUG RESPONSIBLE SEVERE RASH, AGRANULOCYTISIS THIOACETAZONE HEARING LOSS OR DISTURBED BALANCE STREPTOMYCIN
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  DRUGS & SIDEEFFECTSREACTION DRUG RESPONSIBLE VISUAL DISTURBANCE (poor vision and colour perception) ETHAMBUTOL RENAL FAILURE, SHOCK OR THROMBOCYPENIA RIFAMPICIN
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  DRUGS & SIDEEFFECTS REACTION DRUG RESPONSIBLE RENAL FAILURE, SHOCK OR THROMBOCYPENIA RIFAMPICIN HEPATITIS PYRAZINAMIDE
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  • A patientwho develops one of the afore said reactions must never receive that drug again.
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  TB CONTROL PROGRAMME •The National TB Control Programme was mounted in India as early as 1962.
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  • Since thenit has been edified and the treatment strategies has been upgraded as per the programme objectives. One such strategy is DOTS.
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  DOTS
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  PREVENTION
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  BCG VACCINATION • BCGvaccination which was first developed was known as bacille Calmette Guerin. • The initial vaccine was avirulent for man while retaining its capacity to induce an immune response.
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  AIM • The aimof BCG vaccination is to induce a benign, artificial primary infection which will stimulate an acquired resistance to possible subsequent infections with virulent tubercle bacilli and thus reduce the morbidity & mortality due to TB
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  VACCINE • BCG isthe only live bacterial vaccine. • It consists of living bacteria derives from an attenuated bovine strain of tubercle bacilli.
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  TYPES OF VACCINE •There are two types of BCG vaccine : the liquid (fresh) vaccine and freeze dried vaccine. • Freeze dried vaccine is a more stable preparation.
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  • Present dayvaccines are supplied in freezed dried form.
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  • BCG vaccineis stable for several weeks at ambient temperature in a tropical climate and for up to one year if kept away from direct light and stored in cool environment, preferably refrigerated at a temperature below 10 degree C.
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  • The vaccinemust be protected from exposure to light during storage (wrapped up in a double layer of red or black cloth) and in the field.
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  • Normal salineis recommended as a diluent for reconstituting the vaccine, as distilled water may cause irritation.
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  • The reconstitutedvaccine may be used up within 3 hours, and left-over vaccine should be discarded.