Today is our topic of discussion Definition of Tuberculosis
Definition of Tuberculosis
Chronic infection:
Those infections which are slow in progress and persist over time. Example: Tuberculosis and leprosy.
Tuberculosis:
Tuberculosis is a chronic communicable infectious disease, a longer period of caused by Mycobacterium tuberculosis.
Prevalence in Bangladesh:
Bangladesh ranks sixth among countries with a high TB burden. The estimated prevalence rate was 387 per 100000 populations in 2007. Estimates suggest that daily about 880 new TB cases and 176 TB deaths occur in the country.
Epidemiological determinants:
Agent factors:
- Agent: Mycobacterium tuberculosis and Mycobacterium bovis
- Source of infection: Human and bovine
- Communicability: As long as patient untreated
- Infective material:wobowol toge
- Sputum
- Pus, pleural and peritoneal fluid, urine, faeces and gastric contents.
- Meat, milk, milk products (bovine case)
Host factors:
- Age: Affect all ages.
- Sex: More in males.ingso
- Heredity: No role of heredity.
- Nutrition: Malnutrition predispose to TB
- Immunity: Acquired as a result of natural infection or BCG vaccination.
Social factors:
- Poor quality of life
- Poor housing & overcrowding o
- Population explosion
- Undernutrition
- Lack of education
- Lack of awareness about the cause of disease
Mode of transmission:
Inhalation:
Droplets expectorated during coughing, sneezing, talking and singing
Ingestion:
Meat, milk and milk products in bovine cases
[Note: The ‘Mycobacterium bovis’ is the bacteria for ‘bovine tuberculosis’ in cattle, which can also cause tuberculosis in humans transmitted by ingestion of meat and unpasteurized milk]
Primary site of TB:
- Pulmonary tuberculosis (about 80%)
- Extra-pulmonary tuberculosis: When TB occurs as an isolated lesion at body sites other than lung is called extra-pulmonary tuberculosis (EPTB). Ex – Tonsil, bones, intestine, kidney, brain, etc; can happen in the presence or absence of pulmonary disease.
Pathology:
Entrance into body → Bacilli are ingested by the macrophages → Resistant to intracellular destruction by macrophages →→ Tissue destruction and cell mediated immune response occur concurrently →May progress to active disease or some of the bacilli remain ‘dormant’→ When favourable conditions arise, such as, lowered immunity or drug interruption → Bacilli multiply to cause active disease→ 10% of the people infected with TB bacilli may progress to TB disease in ase → 10% of the lifetime.
TB disease:
TB disease means TB infection plus presence of signs and symptoms of TB.
Predisposing factors for PTB:
- Elderly
- Infants
- Immuno-compromised persons: AIDS, chemotherapy, DM, immunosuppressive medications
- Frequent contact with people who have active TB bas
- Poor nutrition
- Live in crowded or unsanitary living conditions
Type of TB infection:
Primary tuberculosis:
Primary tuberculosis occurs in persons never previously exposed to TB bacilli. The lesion is called ‘Ghon complex’ or ‘primary complex’ which has three components
a. Primary focus (Ghon focus): Initial focus of infection is a small sub-pleural granuloma near oblique fissure.
b. Lymphangitis: Inflammation of lymphatic vessel from primary focus to hilar lymph nodes.
c. Hilar lymphadenopathy
Fate of primary complex:
- Healing by fibrosis or calcification .
- Lymphatic spread to cervical or paratracheal
- Progressive pulmonary tuberculosis
- Miliary tuberculosis
- Tubercular meningitis
- Pleural effusion & pneumothorax
- Pericarditis and pericardial effusion
- Post primary pulmonary tuberculosis
Secondary tuberculosis (post primary pulmonary tuberculosis):
Seen mostly in adults as a reactivation of previous infection (or re-infection), particularly when health status declines. Typically, the upper lung lobes are affected and cavitation can occur.
Progressive pulmonary tuberculosis:
The disease continues to progress over months or years. It can develop from non-healed primary focus, re-activation of incompletely healed primary focus or re-infection.
Case definition of tuberculosis by site and bacteriological status in adults
Pulmonary smear-positive TB (PTB+)
A patient with at least two sputum specimens positive for AFB; Or A patient with only one sputum specimen positive for AFB and chest radiological X-ray abnormalities consistent with active TB and diagnosis confirmed by a graduate physician or A patient with only one sputum specimen positive for AFB and a culture positive for M. tuberculosis.
Pulmonary smear-negative TB (PTB-)
A patient with symptoms suggestive of TB with three sputun specimens negative for AFB; and Persisting symptoms after a course of antibiotics; and Again three negative sputum specimens for AFB during repeat sputum examination;
and Chest X-ray abnormalities consistent with active TB; And Diagnosis confirmed by a graduate physician
Clinical features:
History:
History of exposure to TB patients. mi to 25tqu
Symptoms:
- Local features:
- Persistent productive cough for ≥ 3 weeks, despite the antibiotic therapy
- Haemoptysis
- Dyspnoea
- Chest pain
- Wheezing
- General features:
- Low grade fever with evening rise of sung to sin temperature and night sweats
- Gradual loss of weighted
- Loss of appetite
Signs:
- Crepitations or crackles at the apex of involved lung.
- Signs of complication such as, pleural effusion, fibrosis, cavitation.
- Clubbing of the fingers or toes (advanced state)
S/S of extra-pulmonary TB:
In addition to general features, following features are notable-
- TB lymph adenitis: Swelling of lymph nodes and cold abscess breath
- Pleural effusion: Fever, chest pain, shortness of
- TB arthritis: Pain and swelling of joints
- TB of the spine: Radiological findings with or without loss of function
- Meningitis: Headache, fever, stiffness of neck and subsequent mental confusion hou
- Renal TB: Painless haematuria
Investigation:
- Blood TC, DC – Relative lymphocytosis
- Hb% – Reduced
- ESR – Raised (usually high rise)
- X-ray chest P/A view –
– Opacities of varying sizes in upper lobe of
– Hilar lymphadenopathy in primary TB
– Signs of complication: Pleural effusion (fluid level)
- Mantoux test or tuberculin test (MT test) – Skin induration>10 mm is regarded as significant.
- Sputum for AFB
Treatment:
Anti-TB medication:
Fixed dose combinations (FDC) –
6-months regiman :
Fixed dose combination (FDC)
Initial or intensive phase:
Two months (4 drugs) – Ethambutol or Streptomycin + Isoniazid +Rifampicin + Pyrazinamide
[Example: Tab. Rimstar 4 FDC (before meal)]
4+0+0 [If weight > 50 Kg]
3+0+0 [If weight < 50 Kg]
Continuation phase:
Four months (2 drugs) – Isoniazid + Rifampicino
[Example: Tab. Rimactazid 2 FDC (before meal)]
4+0+0 [If weight>50 Kg]
3+0+0 [If weight < 50 Kg]
9-months regimen:
Initial or intensive phase-2 months (3drugs) -E or Z or S plus H + R and continuation phase (7 months) – H+R
DOTS therapy
General supportive therapy:
Improvement of nutrition & housing, Vit-B, supplementation.
Follow-up:
- Patient become non-infectious within two weeks of therapy; it depends on –
- Strict adherence to therapy
- Measurement of body weight: After one month
CXR & ESR: After 1 month: – ESR decreased and CXR – decreased opacity
Indication of steroid therapy in TB:
- Fulminant TB
- To control drug hypersensitivity
- Tuberculous pleural effusion and pericardial effusion
- TB meningitis
- Renal and ocular TB
Dose of anti-TB drugs:
- Isoniazid – H (10 mg/Kg)
- Rifampicin -R (15 mg/Kg)
- Pyrazinamide – Z (25 mg/Kg)
- Ethambutol – E (25mg/Kg)
- Streptomycin -S (30 mg/Kg) [Should not exceed 750 mg daily after the age of 50 years]
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