Tuberculosis
Identification:TB is a major cause of disability and death in most of the world, specially in developing countries. 90% of the initial infection heal leaving no residual changes. About 10% of the initial infection will eventually develop active disease.
Identification:
TB disease may affect any organ or tissue. If untreated, about 65% of sputum smear +ve pulmonary TB die within 5 years. Symptoms: fatigue, fever, night sweating and weight loss + localized symptoms as cough, hemoptysis.TB may affect any organ or tissue; in order of frequency: 1- Lymph nodes 2- Pleura 3- Genito-urinary tract 4- Bones and joints 5- Meninges 6- Gastro-intestinal tract 7- Peritoneum 8- Pericardium
Systemic presentations of extrapulmonary TB.
History Improving in social conditions and nutrition → decrease risk of TB infections and deaths. Dramatic decrease in TB infections and deaths after introduction of BCG vaccination.
Dx:
Clinical → [unexplained fever + night sweating + cough] for > 3 weeks → suspected TB.CXR → pul. infiltration and cavitations … most commonly in the upper segments of the lobes.Sputum smear (AFB).Sputum culture.Tuberculin test.Others as biopsy.
Chest X-ray: major manifestations and differential diagnosis of pulmonary TB.
Sputum smear for AFB:To detect the bacilli in sputum smear need ≥ 10 000 bacilli / mL.Only 50 – 80% of patients with active pulmonary TB will have a +ve smear test. *At least 2 smears but preferably 3, including an early morning sample .
Positive Ziehl-Neelsen stain. Mycobacteria retain the red carbol fuschin stain despite washing with acid and alcohol.
Tuberculin skin test (T.T) Type: Purified Protein Derivative standard (PPDs) Dose : 5 T.U Methods: Standard method-quantitative intradermal test (Mantoux test). Multiple puncture test (Heaf test).
Technique :Heaf test –(for surveys) Read after 3-7 days, 4 – 6 indurated papules at punctures.Atypical grade 1 : 4 – 6 papules+/- grade 2 : confluent papules → ringInfected by grade3 : central indurationTubercle B. grade 4 : indurated +necrosis (> 10 mm)Mantoux testIntradermal injection on flexor of forearm.Read after 2-4 days.Positive test when raised area of inflammatory edema not less than 10 mm surrounded by Erythematic ring.
Skin testing in TB
Negative.Grade 1.
Grade 2.
Grade 3.
Grade 4.
+ ve tuberculin testActive TB.Old healed TB (primary focus).BCG vaccine.Atypical M. infection.- ve tuberculin test10 – 20% of active TB (false - ve).TB meningitis and miliary TB.Newborn and elderly.HIV and immune suppressive drugs.In developing countries T.T has limited use in the diagnosis of TB.
2. Infectious agent: Mycobacterium tuberculosis in human Tubercle bacilli M. bovis in cattle M. Avium in birds Human infection with M. bovis is still a problem in areas where the disease in cattle has not been controlled and milk and milk products consumed raw.
Structure of the TB Bacillus
M. tuberculosis is a thin aerobic organism. Multiply slowly and acid-fast. Thin rods that can occur in clusters and alone. Sensitive to sun, ultraviolet light.3. Occurrence: worldwide
Commonest communicable disease in the world,In 2016 global data:Prevalence 10.0 million of infectious TB.Incidence 9.2 Million / year.Death 1.7 million / year.Over 95% of cases and deaths are in developing countries.Infected children or adult (latent T.B) life time risk of T.B is 10 %.Latent T.B + HIV → life time risk of T.B is 50 %.World-wide incidence of TB. estimated new cases (all form) /100 000 population (WHO).
3- Occurrence cont.,.In Iraq – 2011: no. of new cases was15 000.In Nineveh – 2010: no. of the reported new cases of active TB was 463.92% of them above 15 years of age. TB disease caused by M. bovis accounts for approximately 1% of all reported TB cases.
4. Reservoir:primarily humans, in some areas diseased cattle.5. Mode of transmission:Air-borne transmission by droplet nuclei 1 – 5 microns in diameter (person with pul. Or laryngeal TB) → coughing, singing or sneezing → inhaled via contacts → pul. Alveolae → alveolar microphages → initiating a new infection. It required prolonged close contact.laryngeal TB is highly contagious but rare.Bovine TB (infected cattle) → either ingestion of raw milk or dairy products (unboilled or unpasteurized), or air-borne infection to farmers.contact infection: Direct contact of braded skin and mucosa are extremely rare.Note: extrapulmonary TB not contagious except where there is draining sinus.
How Are TB Germs Spread?
6. Incubation period: From infection2 -10 weeks primary lesion 7. Period of communicability: As long as the bacilli present in the sputum (+ve smear for AFB). Effective Rx eliminates communicability within 2 – 4 weeks.8. Susceptibility: Latent TBProgressive pul. TB
Life long
1 – 2 Y
Factors affecting the develop. of active T.B: Immunity as TB + HIV, underweight or undernourished. Dose Age: Tuberculosis mostly affects adults in their most productive years. However, all age groups are at risk. Socio-economic status: Over crowding, malnutrition, bad ventilation. Morbidity and mortality rates are higher among poor and minority populations. Usually higher in urban areas. Smoking. Heredity no rule. Individual conditions [Silicosis, type I D.M, gastrectomy, malabsorption, high-dose steroids, certain cancers].
9. Methods of control A- Preventive measures:
Health education of suggestive symptoms to people: unexplained cough > 3 weeks.Also health education on curability of TB.Improving socio – economic conditions.Maximum number of case detection and RxSputum smear is the mainstay of Rx, it’s the most cost- effective method of case finding and is 1st priority in developing countries.Why not sputum culture?Why not mass miniature CXR?9. Methods of control A- Preventive measures:
Maximum number of case detection and RxRisky groups, do whatever investigations:Contacts of an active case.Medical workers.Military forces and school teachers.Young adults on university admission.Successful treatment:Problems of Rx → defaulters.Solutions of defaulters : Rx under supervision (DOTS). Involving local community. Mobile and peripheral Rx centers. Checking drug consumption. Rx resistant cases.
Chemoprophylaxis (for close contacts especially < 5 years)Isoniazid tab. for 6 – 12 months was effective in preventing progress of latent TB into active TB. (be aware from side effect as hepatitis, allergy, skin rash).During pregnancy; postpone treatment until after delivery.Mass chemoprophylaxis is unrealistic.Pasteurization /sterilization of milk/ M. bovis.B.C.G (Bacillus Calmette Guйrin).
B.C.G (Bacillus Calmette Guйrin)Live attenuated vaccineIndications: Given to all new born babies in developing countries including Iraq within 1st week of life. Dose: 0.1 ml adult / 0.05 ml children / ID/ Deltoid.Red papule → vesicle → 4 – 8 weeks → deep permanent scar.Protection : ?? up to 80%. In Iraq 60 – 70 %.Protect against severe form of TB as TB meningitis and miliary TB.Immunity : 12 -20 years.Complications: Suppurative lymphadenitis 0.1 - 4.3 % among < 2 years children, local abscess.Not routinely indicated in developed countries [used for high risk groups].
Reporting: Cass II.Isolation: Hospitalization only for severe illness, otherwise its ambulatory Rx. Stick respiratory precaution until sputum – ve and no cough.Disinfection of purulent discharges.Quarantine: not applicable.Management of contacts: Chemoprophylaxis can be given after ruling out of TB disease especially for under 5 aged contacts.Specific treatment: B- Control of patients, contacts and environment:
Face respirator
Rx Objectives of individual RxAnti :T.B drugs should be used in combination (≥ 3 drugs)Continue (2drugs)H = isoniazid, R = rifampicin, Z = pyrazinamide, E = ethambutol, S = streptomycin.It is an ambulant chemotherapy
Follow –up of the patientDuring Rx-very important by monthly sputum smear.After Rx ±.Note: if smear +ve at month 5 → Rx failure.
DOTS: Directly Observed Therapy-Short course.New patients with pulmonary TB should receive a regimen containing 6 months of rifampicin: 2HRZE/4HR.Wherever feasible, the optimal dosing frequency for new patients with pulmonary TB is daily throughout the course of therapy.Two alternatives:2M →H + R + Z + E(Daily )4M →H + Z(three times weekly)Provided that each dose is directly observed.OrThree times weekly dosing throughout therapy [2(HRZE)/4(HR)] provided that every dose is directly observed.
This regimen (2HRZE/4HR ) is also applies to extrapulmonary TB except TB of the central nervous system, bone or joint for which some expert groups suggest longer therapy.
DOTS:Advantages Effective (95% cure rate).Cost –effective (20 $ for 6 M treatment). Easy to apply and used. Can be applied by paramedics.Doesn't require hospitalization or isolation.Shorter duration.DOTs help prevent drug resistance.
Pregnancy: all safe except streptomycin. Lactation: all safe + baby [BCG & INH]. OCP: rifampicin decrease effectiveness of pills so increase possibility of pregnancy so use higher dose of estrogen or use other method of contraception.