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Childhood TB: Introduction to childhood tuberculosis
 

Childhood TB: Introduction to childhood tuberculosis

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Childhood TB was written to enable healthcare workers to learn about the primary care of children with tuberculosis. It covers: introduction to TB infection, the clinical presentation, diagnosis, ...

Childhood TB was written to enable healthcare workers to learn about the primary care of children with tuberculosis. It covers: introduction to TB infection, the clinical presentation, diagnosis, management and prevention of tuberculosis in children

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    Childhood TB: Introduction to childhood tuberculosis Childhood TB: Introduction to childhood tuberculosis Document Transcript

    • 1 Introduction to childhood tuberculosisBefore you begin this unit, please take the TUBERCULOUS INFECTIONcorresponding test at the end of the book toassess your knowledge of the subject matter.You should redo the test after you’ve worked 1-1 What is tuberculosis?through the unit, to evaluate what you havelearned. Tuberculosis (TB or TB disease) is a chronic infectious disease which may involve many organs of the body, but most often affects Objectives the lungs. Tuberculosis of the lung is called pulmonary tuberculosis. When you have completed this unit you Tuberculosis is a chronic infectious disease. should be able to: • Explain what tuberculosis is. 1-2 What causes tuberculosis? • Describe how TB bacilli are spread. • Explain the difference between TB Tuberculosis is a bacterial illness caused by Mycobacterium tuberculosis. These bacteria infection and tuberculosis. are also referred to as TB bacilli (tuberculous • Explain why children are at high risk of bacilli). TB infection. • List communities in which tuberculosis Tuberculosis is caused by TB bacilli. is common. • Explain the features of pulmonary NOTE Mycobacterium tuberculosis was tuberculosis. first described by Robert Koch in 1882. • List the common forms of extrapulmonary tuberculosis. 1-3 How are TB bacilli spread? Tuberculosis is an infectious disease which results from the spread of TB bacilli from one person to another. TB bacilli are usually spread
    • 16 CHILDHOOD TBwhen a person with pulmonary tuberculosis home. A mother with untreated pulmonarytalks, coughs, spits, laughs, shouts, sings or tuberculosis who is in close contact with hersneezes. This sends a spray of very small children is a great danger to her children.droplets from the person’s infected lungs into Children in close, prolonged contact withthe air (i.e. airborne droplet spread). Live TB adults who have untreated pulmonarybacilli in these droplets then float in the air tuberculosis are at greatest risk. Youngerand may be breathed in by other people. If the children are more likely to spend most of theinhaled TB bacilli reach the alveoli they cause day and night with an adult.a tuberculous infection of the lung.1-4 Who usually spreads TB bacilli? Children in poorly ventilated, overcrowded homes are at greatest risk of infection with TB bacilli.TB bacilli are usually spread from adults withuntreated pulmonary tuberculosis. Therefore,a child with tuberculosis almost always has 1-7 Do all children infected withbeen in close contact with an adult with TB bacilli develop tuberculosis?pulmonary tuberculosis (the source of the TB No. Most children infected with TB bacillibacilli). It is less common for a child to catch do not develop tuberculosis (TB disease)tuberculosis from another child as children because their immune system is able to controlusually do not cough up TB bacilli in large the infection and kill most of the TB bacilli.numbers. Therefore, adults with untreated As a result, the natural immune responsetuberculosis are a danger to children in the protects most children with TB infection fromfamily or household. progressing to tuberculosis. It is very important to understand that a child TB bacilli that infect children are usually spread can only develop tuberculosis if the child is from an adult with untreated pulmonary first infected with TB bacilli. Furthermore, tuberculosis. TB infection does not always progress to tuberculosis (TB disease). Therefore TB NOTE TB bacilli in unpasteurised or unboiled infection without further progression is not cows’ milk (Mycobacterium bovis) can be the same as tuberculosis. drunk and cause infection of the tonsil or gut, but this is very uncommon in South Africa. Fortunately most children infected with TB bacilli1-5 Which children are at greatest do not develop tuberculosis.risk of infection with TB bacilli? The progression of TB infection to tubeculosisChildren, especially those under five years of is more common in children than in adults.age, who are exposed to large numbers of TBbacilli. 1-8 Which children with TB infection are at the greatest risk of developing tuberculosis?1-6 Which children are exposed tolarge numbers of TB bacilli? Children with a weak immune system are at the greatest risk. In these children,Children who live in overcrowded, infection with TB bacilli may progress topoorly ventilated homes or are exposed tuberculosis because they have an inadequateto crowded buses, taxis, schools, crèches immune system which is unable to controland spaces where there are adults with the infection. TB infection caused by largeuntreated pulmonary tuberculosis. A child numbers of TB bacilli is also more likely towith tuberculosis often has an adult with progress to tuberculosis.untreated tuberculosis living in the same
    • INTRODUCTION TO CHILDHOOD TUBERCULOSIS 17Therefore, both TB infection and progress to The risk of TB infection progressing totuberculosis are most common when a child tuberculosis is greater in young childrenwith a weak immune system is exposed to than in older children or adults. In childrenlarge numbers of TB bacilli. infected under two years of age, the risk is as high as 50%. Children with weak immune systems are at greatest risk of tuberculosis. About 10% of people with TB infection will develop tuberculosis.1-9 Which children have weakimmune systems? 1-12 What do you understand by the incidence of tuberculosis?Young children under five years, and especiallyif under two years, of age have immature The incidence is the number of people with(weak) immune systems which are unable to tuberculosis per 100 000 of the population percontrol severe infections. The immune system year. This is a very useful measure as it allowscan further be weakened in: the frequency of tuberculosis in different communities or countries to be compared. The• Children with HIV infection incidence of a single community can also be• Children recovering from measles or compared from one year to the next. whooping cough• Children with severe malnutrition• Children on large doses of oral steroids 1-13 What is the incidence of tuberculosis in South Africa?HIV infection is the most important cause of aweakened immune system. While tuberculosis is uncommon in most developed countries, it is common in developing countries such as South Africa Children with HIV infection have the highest risk where the number of people with tuberculosis of developing tuberculosis. has increased rapidly in the last few years. The incidence of tuberculosis in South Africa1-10 Is TB infection common? was 948/100 000 in 2007. This is high when compared to developed countries like theYes, infection with TB bacilli (Mycobacterium United Kingdom where the incidence oftuberculosis) is very common, and it is tuberculosis in 2007 was 13/100 000.estimated that almost 50% of adult SouthAfricans have been infected. Most infections In South Africa tuberculosis is particularlytake place during childhood. common in the Western Cape and KwaZulu- Natal. It is estimated that there are 400 new cases of tuberculosis per 100 000 children TB infection is common and usually occurs during each year in the Western Cape. In any clinic childhood. children will make up approximately 15% of all the cases of tuberculosis.1-11 How many children with TB NOTE About ten million new cases ofinfection develop tuberculosis? TB occur worldwide each year with two million deaths due to TB. About 300 SouthOnly about 10% of all people with TB Africans die of TB each day. With the AIDSinfection progress to tuberculosis (TB disease) epidemic this figure is rising rapidly.during their lifetime. Therefore, TB infectionis far more common than tuberculosis.
    • 18 CHILDHOOD TB1-14 In which communities is area of inflammation. This is called primarytuberculosis common? tuberculosis. From the primary infection TB bacilli spread along the lymphatics to the localTB is common in poor, disadvantaged lymph nodes at the place where the maincommunities where overcrowding, bronchi divide into branches (hilar nodes).undernutrition and HIV infection are The primary infection in the lung, togethercommon. Tuberculosis is a disease of poverty. with the infected hilar lymph nodes, is calledTuberculosis spreads in any overcrowded the primary complex. Parahilar and otherliving spaces, both at home and in the mediastinal nodes may also be affected.community. TB is often transmitted bya child’s family member, friend or close After six weeks the immune system usuallyneighbour. However it may also be caught becomes active and kills most of the TB bacilliin a public space if there are many untreated in the lung and lymph nodes. As a result, thepatients in the community. primary infection is asymptomatic in most children and does not cause clinical illness. Tuberculosis is usually seen in poor communities. Therefore, the primary TB infection usually heals and does not spread any further, as the NOTE About 95% of new TB cases and 99% TB bacilli have been contained by the body’s of TB deaths worldwide are in developing natural immunity. countries. In developed countries TB is NOTE The primary TB infection in the lung virtually confined to poor, overcrowded used to be called the Ghon focus. environments and ethnic minorities.1-15 Why is tuberculosis an Inhaling TB bacilli into the lung may result inimportant disease? primary infection.Tuberculosis is a major cause of illness anddeath in many poor countries. These are 1-17 Can the primary TB infectionpreventable deaths, and the large number of cause illness due to spread of thepatients with tuberculosis is a huge drain on infection within the lung?healthcare resources. Sometimes the primary TB infection is not controlled by the immune system and the Tuberculosis is an important cause of illness and child now becomes ill with the signs and death. symptoms of pulmonary tuberculosis. This is a common form of tuberculosis in children. With progression of the primary infectionPULMONARY to pulmonary tuberculosis, the TB bacilli continue to multiply and an area ofTUBERCULOSIS inflammation develops in the lung and lymph nodes in an attempt to prevent the TB bacilli from spreading any further. Often the centre1-16 What is primary TB infection of the inflamed area becomes soft as the tissuesof the lung? die. These dead cells (caseous material) canTuberculous infection usually starts when TB drain into the surrounding tissues.bacilli are inhaled deep into the distant parts There are a number of different ways that theof the lungs, called alveoli. During the first six primary TB infection can spread (progress)weeks of infection the immune system is unable and lead to complications.to control the TB bacilli, which multiply rapidlyin the alveoli where they cause a small, local
    • INTRODUCTION TO CHILDHOOD TUBERCULOSIS 19 measles, the TB bacilli may start to multiply The primary TB infection may spread to cause once more (reactivation) and a local area pulmonary tuberculosis. of tuberculous pneumonia will develop. Therefore, pulmonary tuberculosis due to NOTE The immune response to TB bacilli reactivation of dormant TB bacilli may only is dependent on T lymphocytes. present years after the primary infection.1-18 What are the pulmonary complicationsof the primary TB infection in the lung? Pulmonary tuberculosis with enlarged hilar lymph nodes is the commonest form of• In some children with a weak immune system, the body is unable to control the tuberculosis in children. primary infection in the lung. The TB bacilli continue to multiply and spread 1-19 What are the pulmonary complications into neighbouring parts of the lung to of TB infection in the hilar lymph nodes? cause tuberculous pneumonia. Progression • TB bacilli may multiply rapidly in the hilar from the primary infection to pulmonary lymph nodes, causing the nodes to enlarge tuberculosis usually takes place rapidly and compress the bronchus or trachea within weeks or months and the child (airway). Clinically this may present as becomes ill. This pattern of tuberculosis, wheezing or stridor with either collapse or together with enlarged hilar nodes, is the hyperinflation of a lobe or the whole lung. commonest form of tuberculosis in young • The enlarged lymph node may rupture and undernourished children. into a bronchus spreading large numbers• Cavitary tuberculosis (‘open tuberculosis’) of TB bacilli into other areas of the lung. is usually seen in older children and This results in widespread tuberculous adolescents. The area of tuberculous bronchopneumonia. pneumonia progresses and breaks down to form a hole. This occurs most commonly in the upper parts of the lung and results Enlarged hilar lymph nodes may compress the in an air-filled cavity containing dead airways causing wheezing. (caseous) tissue which contains huge numbers of TB bacilli. This form of 1-20 Why are the lungs the pulmonary tuberculosis is very infectious commonest site of tuberculosis? as TB bacilli grow fast and many TB bacilli enter the airways. From here they are The lungs are the commonest site of coughed into the air where they may be tuberculosis as TB infection is usually caused breathed in and infect the lungs of other by inhaling TB bacilli. people. Children and adolescents with cavitary tuberculosis are very infectious 1-21 What is the difference and can infect other children and adults. between pulmonary tuberculosis• Damage to the large airways by in children and adults? tuberculosis can result in bronchiectasis.• In older children and adults the TB While children usually have lymph node bacilli often remain dormant (inactive or enlargement with few TB bacilli in the sputum, ‘sleeping’) in the lung for many months or adolescents and adults usually have cavitary even years after the primary infection. The tuberculosis with destruction of lung tissue and body has been able to control but not kill large numbers of TB bacilli in their sputum. all the TB bacilli. If the immune system later becomes weakened by malnutrition or another infection, such as HIV or
    • 20 CHILDHOOD TB NOTE Cavities are formed in adult-type 1-23 Which other organs can be tuberculosis, usually in the upper lobes or apices involved in tuberculosis? of the lower lobes of the lungs. This can result in permanent lung damage and scarring (fibrosis). Although the lung is the commonest organ infected by TB bacilli, tuberculosis can involve any other organ of the body. SometimesEXTRAPULMONARY more than one organ is infected. The organs which are most commonly infected via theTUBERCULOSIS bloodstream in children are: • The meninges (tuberculous meningitis)1-22 Can tuberculous infection spread • Bones, especially the spine (tuberculousfrom the lung to other parts of the body? osteitis) • Joints, especially the hip joint (tuberculousYes. This spread beyond the lungs is called arthritis)extrapulmonary tuberculosis: • Intra-abdominal organs such as liver• Tuberculosis may spread from the lung to and spleen and peritoneum (abdominal the pleura causing a pleural effusion. tuberculous)• Infection with TB bacilli can spread NOTE The skin, tonsils, pericardium, bone from the lung, and especially the hilar marrow, middle ear and genitalia are less lymph nodes, via the bloodstream (TB common sites of tuberculosis in children. bacteraemia) to most organs of the body. Tuberculosis of the kidney usually follows In children the TB bacilli usually spread five or more years after the primary infection at the time of the primary lung infection. and therefore is uncommon in childhood. As a result, tuberculosis of other organs usually presents soon after the primary 1-24 What is disseminated tuberculosis? lung infection. However, the TB bacilli Tuberculosis involving multiple organs is may remain dormant in these organs for referred to as disseminated tuberculosis. many months or years before they start to This follows spread of TB bacilli through the multiply and cause local tuberculosis. This bloodstream to many organs. If disseminated reactivation of TB bacilli is usually due to tuberculosis includes widespread infection of weakening of the immune system. both lungs, it is called miliary tuberculosis.• TB bacilli can also spread to other lymph This is a very serious illness with a high nodes via the lymphatics (e.g. from the mortality rate unless diagnosed and treated hilar lymph nodes up to the cervical lymph early. It usually occurs in young children. nodes or down to the abdominal lymph nodes). Lymph nodes in the axilla or groin may also be involved. However, lymphatic Disseminated tuberculosis is a serious illness spread is usually to the cervical nodes. with a high mortality rate. TB infection of lymph nodes is called tuberculous lymphadenitis. 1-25 Is extrapulmonary tuberculosis infectious? Tuberculous bacilli may spread from the lungs Unlike pulmonary tuberculosis, tuberculosis of to other organs via the bloodstream or the other organs is rarely infectious to other people. lymphatics.
    • INTRODUCTION TO CHILDHOOD TUBERCULOSIS 211-26 Is extrapulmonary tuberculosis mother to cough over her newborn infant.common in children? TB bacilli do not appear in the breast milk. Therefore breastfeeding is safe as long asYes, extrapulmonary tuberculosis is far more the mother is on treatment and the infantcommon in children than in adults. Cervical receives prophylaxis.lymph node enlargement is the commonestform of extrapulmonary tuberculosis inchildren. CASE STUDY 1 Cervical lymph node enlargement is the A child of six years develops primary TB commonest form of extrapulmonary tuberculosis infection in her one lung. She remains in children. clinically well however. When she is weighed by the school nurse, the mother is reassured1-27 Can one have a tuberculous that the child is healthy and thriving.infection more than once? 1. What is the cause of TB infection?Yes. Previous TB infection does not givecomplete immunity to further TB infections. TB bacilli (Mycobacterium tuberculosis).A child with a healed primary infection can,months or years later, have another new 2. Why is this child clinically well ifprimary infection when they are exposed to she has a primary TB infection?an infectious case of tuberculosis, especially Because most children with a primary TBif their immune system is weakened by severe infection have no signs or symptoms ofmalnutrition or HIV. illness. Her immune system has controlledTherefore, pulmonary tuberculosis may be the TB infection.due to immediate spread from the originalprimary infection, reactivation (relapse) 3. Will this child develop tuberculosis?of an old primary infection which had nothealed fully (latent tuberculous infection), Probably not, as most children are able toor spread from a new primary infection prevent the spread of TB bacilli from the(reinfection). In children, spread from the primary infection.primary TB infection to cause tuberculosis ismost common and usually occurs within two 4. Which children are at greatestyears of being infected (90% within one year of risk of the primary infectionbeing infected). progressing to tuberculosis? Children with weak immune systems. These1-28 Can a mother with tuberculosis infect include young children, malnourishedher infant either before or after birth? children and children with HIV infection.Yes. During pregnancy TB bacilli in the mothercan be spread via the bloodstream to the 5. How common is TB infection?placenta. From here the TB bacilli may reach Very common. Almost 50% of adult Souththe fetus via the umbilical vessels or may infect Africans have had a primary TB infectionthe amniotic fluid and then be swallowed by at some time in their lives, most duringthe fetus. Infection during delivery is rare. childhood.However, the spread of TB bacilli from amother to her infant usually happens afterdelivery. The greatest risk is for an infectious
    • 22 CHILDHOOD TB6. How many children with TB 4. Is childhood tuberculosisinfection develop tuberculosis? common in South Africa?The risk of progression from TB infection to Yes, especially in poor, disadvantagedtuberculosis during a lifetime is about 10%. communities. Childhood tuberculosis makesHowever the risk is higher in children and is up approximately 15% of all the cases at a TBas high as 50% in children under two years clinic.of age. Therefore TB infection is particularlydangerous in young children. 5. What are the pulmonary complications of primary TB infection in the lung?CASE STUDY 2 The primary infection in the lung may progress to tuberculous pneumonia. In older children and adults this may form a cavity. TheAn 18-month-old child lives in an overcrowded grandfather probably has cavitary tuberculosis.home. During the day he is looked after byhis grandfather who is unwell and has had 6. Are the hilar lymph nodes oftena chronic cough for the past few months. involved in primary TB infection?The clinic nurse is worried as the child ismalnourished and recently had measles. Yes. The primary TB infection in the lung is usually associated with enlarged hilar1. Why is this child at high lymph nodes. Together they are called therisk of TB infection? primary complex. The enlarged hilar nodes can compress a large airway causing wheezeBecause the grandfather probably has or stridor. Further enlargement of the lymphundiagnosed pulmonary tuberculosis. The nodes may result in collapse or overinflationhouse is overcrowded and the child has of a lobe.prolonged contact with the grandfather. Thesefactors all suggest that the child is beingexposed to large numbers of TB bacilli. CASE STUDY 32. Why will the TB infection probably The parents are very worried as theirprogress to tuberculosis? daughter has a lump in her neck which hasBecause the child has a weak immune system been diagnosed as tuberculosis. Friends telldue to his young age, malnutrition and recent them that the diagnosis must be wrong asmeasles infection. tuberculosis only affects the lungs.The child’s age and exposure to large numbersof TB bacilli will, therefore, increase his 1. Does tuberculosis only affect the lungs?risk of both TB infection and progress to No. Tuberculosis may affect most organs of thetuberculosis. body. Tuberculosis outside the lungs is called extrapulmonary tuberculosis.3. What other infection mayweaken the immune system? 2. What is the likely cause ofHIV. the lump in her neck? Tuberculosis of a lymph node (tuberculous lymphadenitis).
    • INTRODUCTION TO CHILDHOOD TUBERCULOSIS 233. What other organs are most THE FIVE MOSTcommonly infected with TB? IMPORTANT ‘TAKE-The meninges (TB meningitis), bones (TBosteitis), joints (TB arthritis) and abdominal HOME’ MESSAGESorgans (abdominal TB). 1. Children are infected with TB bacilli after4. What is disseminated tuberculosis? exposure to someone with infectious pulmonary tuberculosis.The spread of TB infection to many organs. 2. Most TB infection in children does notThis is a serious illness with a high mortality progress to disease (tuberculosis).rate. 3. The children at greatest risk of progression to disease are children infected when5. Is extrapulmonary tuberculosis less than two years of age, HIV infectedinfectious to others? children, and children with malnutrition.Usually not. However, extrapulmonary and 4. Pulmonary tuberculosis with enlargedpulmonary TB may occur in the same patient. hilar lymph nodes is the commonest formPulmonary tuberculosis is the most infectious of tuberculosis in children.form of the disease. 5. Cervical lymph node enlargement is the commonest form of extrapulmonary tuberculosis in children.6. Can a newborn infant be infectedwith tuberculosis from the mother?Tuberculosis can spread from mother to infantduring pregnancy but this is uncommon.The greatest risk is when a mother withtuberculosis coughs onto her newborn infant.