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Tuberculosis and Youth
Keith W. Wilson BA MD PhD CCFP
Sept 2011
Outline
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What is TB?
TB Facts
TB in Children
TB Control
TB Prevention
Conclusions
What is TB?
What is TB?
• Mycobacterium tuberculosis
– Discovered in 1882 by Robert Koch (18431910), German Physician
• M. tuberculosis accounted for 1 in 7 deaths in
Europe at that time (about 1:3 for young productive
adults)
• Acid-Fast Bacillus
Classic Features of TB
• TB can affect any organ system: bone,
kidney, CNS; 80% are pulmonary
• Active disease presentation:
– persistent cough > 3 weeks duration
– +/-haemoptysis, decreased appetite, weight
loss, general weakness, night sweats
• Active disease atypical presentation:
diminished clinical signs, much more
common in HIV-infected
TB Transmission
• Spread through the air
• Enters through the lungs
• Person with untreated pulmonary TB
disease can infect 10-15 people each year
TB Infection vs. TB Disease
• TB infection – organism is present, but
dormant, cannot infect others
• TB disease (active TB) – person is sick
and can transmit disease to others if in
lungs
• Lifetime risk of developing (active) TB
disease if TB infected but HIV neg: 10%
• Annual risk of developing TB disease if coinfected with HIV: 10%
When does TB Infection become
Disease?
• Most likely in first two years after infection
• If person becomes immunocompromised
– HIV
– Cancer
– Chemotherapy
– Poorly controlled diabetes
– malnutrition
TB Facts
TB Facts
• 2 billion people (1/3 of the world’s
population) are infected with TB bacilli
• 1 in 10 people infected with TB bacilli will
become ill with active TB
• TB is a disease of poverty; mostly
affecting young adults during their most
productive years
• Death due to TB is mostly found in
developing countries with nearly half
occurring in Asia
Source: World Health Organization 2007
TB Facts
• In 2009
– 1.7 million people died from TB (4600 deaths
per day)
– 9.4 million new cases of TB (80% of these
were in 22 countries)
• Global incendence rate fell to 137 cases
per 100,000 in 2009
• Highest level of people successfully
treated was 86% achieved in 2008
Source: World Health Organization 2010
Estimated TB Incidence 2009
TB is a Worldwide Problem
Source: World Health Organization 2010
TB in Children
TB in Children
• Estimated 1 million children worldwide with TB
– 75% of these occur in the 22 high-burden countries
– In low-burden countries, childhood TB constitutes
about 5% of the caseload, compared to 20-40% in
high-burden countries
• Estimated 130,000 deaths per year in children
worldwide
– High correlation with socioeconomic status, nutritional
status & immunosuppression
Source: Swaminathan S, Rekha B (2010)
Canadian Context
• Most cases of paediatric cases of TB in
Canada are found in:
– Aboriginal children
– Foreign-born children
– Canadian-born children of foreign-born
parents
Source: Canadian Tuberculosis Standards, 6th Edition (2007)
TB in Canada
Source: Canadian Tuberculosis Standards, 6th Edition (2007)
TB in Canada
Adapted from: Tuberculosis in Canada 2009 – Pre-Release (2010)
TB in Canadian Children
Adapted from: Tuberculosis in Canada 2009 – Pre-Release (2010)
TB in Canadian Children
Adapted from: Tuberculosis in Canada 2009 – Pre-Release (2010)
Challenges to TB Control
• Three major challenges exist in TB control
unique to children:
– TB diagnosis in children is difficult
– TB in children is considered a sentinel/recent
event
– Increased risk of latent TB infection (LTBI)
Source: Canadian Tuberculosis Standards, 6th Edition (2007)
TB Diagnosis in Children
• A Major Challenge!
– Less than 15% cases are smear positive and
culture yields are only 30-40%
– In non-endemic countries, without
bacteriologic confirmation, triad of:
• Close contact with infectious index case
• Positive tuberculin skin test
• Presence of suggestive abnormalities on CXR
Source: Swaminathan S, Rekha B (2010)
TB Diagnosis in Children
• Clinical Presentation
– Most children are asymptomatic at
presentation, typically identified as a contact
by public health
– Later found to have abnormal chest xrays
– Older children and adolescents are more
likely to manifest adult presentation (fever,
night sweats and weight loss)
TB Diagnosis in Children
• Pulmonary parenchymal disease: most common
manifestation at 60-80% cases
• Extra-pulmonary manifestations:
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Lymphadenopathy (67%)
CNS involvement (13%)
Pleural involvement (6%)
Miliary and/or disseminated (5%)
Skeletal (4%)
Source: Swaminathan S, Rekha B (2010)
Complications in Children
• Parenchymal lesions may enlarge and caseate
• Nodes may enlarge and compress or erode
through a bronchus (causing wheeze,
pneumonia or atelectasis)
• Subclinical bacteraemia which seeds distant
sites (apices of lungs, lymph nodes and CNS)
• The above is most common in < 5yo
Source: Canadian Tuberculosis Standards, 6th Edition (2007)
Diagnostic Tools
• Tuberculin skin test (TST) remains standard tool
• Interferon-Gamma Release Assays (IGRA)
– can be helpful, particularly in those previously
immunized with BCG vaccine
– However immature immune response in infants and
young children pose a challenge
• Chest Xrays
– Difficulty in interpretation remains
• CT Scan
– Not routinely recommended
Source: Canadian Tuberculosis Standards, 6th Edition (2007)
Diagnostic Tools
• Others
– Gastric aspirates: people swallow mucus in their
sleep
– Sputum Induction: sometimes useful in older children
– Cultures: Nucleic acid amplificiation tests/PCR (but
limited in paucibacillary disease)
Source: Paediatr Child Health 2003; 8(3): 162-172
TB Screening
• Targeted TB Screening in Children
– Contacts of known cases of active TB
– Children with suspected active TB disease
– Children with known risk factors for progression of
infection to disease
– Children travelling or residing for 3+ months in an
area with a high incidence of TB
– Children who arrived in Canada from countries with
high TB incidence within past 2 years
Source: Paediatr Child Health 2010; 15(8): 529-33
TB Control
Priorities of TB Control
• Completion of treatment is paramount!
• Treating non-pulmonary cases and those with
infection, without active disease are of lesser
public health importance! (unless you are a
child!)
• A poor TB program worse than no TB program—
bad programs breed resistance!
• These priorities hold regardless of HIV status!
TB Control
• Directly Observed Treatment, Short-course
(DOTS)
– Once diagnosed, community works observe and
record patients swallowing their full course of TB
medications
– Usual medications include isoniazid, rifampicin,
pyrazinadmide, streptomycin and ethambutol
– A six-month supply of medications costs $11 USD per
patient: one of the most cost-effective of all health
interventions
– Completion of all prescribed medications reduces the
incidence of resistance
DOTS Strategy
1. Political commitment with increased and
sustained funding
2. Case detection through quality-assured
bacteriology
3. Standardized treatment with supervision and
patient support
4. Effective drug supply and management system
5. Monitoring and evaluation system, and impact
measurement
DOTS Effectiveness
• 26 million TB patients have been treated
under DOTS since 1995
• 187 countries have adopted DOTS
– Many need to expand DOTS services
however
• Dissemination through WHO and STOPTB programmes
Turning the corner?
Millions of new cases per year
4
Rest of world
3
Africa
2
1
E Europe
0
1990
1995
2000
2005
TB Prevention
TB Prevention
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Contact Tracing
Screening
Vaccines – BCG
Treating LTBI
Contact Tracing
• Childhood case likely to be recent infection
– Rigourous search of index case
– Child as index case unlikely to be particularly
contagious
• All exposed children should be identified and
risk ascertained
– Children <5yo with neg TST and neg CXR should
consider taking “window” preventive therapy (8 weeks
– as it may take that long for the exposed to convert
their TST to positive)
Latent TB Infection
• Latent TB Infection (LTBI)
– A few bacilli sequestered “somewhere”
– Walled off by host defenses
– Not clinically detected
– Positive test: TST or IGRA
Future Dilemmas
• MDR/XDR-TB is in Canada – unclear how
many cases are paediatric
• Co-infection with HIV
• Difficult to overcome the overall burden of
TB without considering the Social
Determinants of Health
Concluding
Remarks
Source: CMAJ (2011); 183(7): 741
In Summary
• Children are not just ‘little adults’ when it comes
to TB
• TB is challenging to diagnose in the paediatric
population
• New tools on the horizon will help combat TB in
children
• We have a long way to go in Canada to
overcome the burden of TB in our most
vulnerable populations – get involved in
advocacy!
Thank you
Questions?
Dr Keith W Wilson
[email protected]