Infections In Childhood

Question 1

What are the main causes of childhood death in the countries with the worst child mortality rate? (Somalia, Mali and Burkina Faso)

Answer 1

War, poverty and political instability

Question 2

What are the child mortality rates of the countries with the lowest child mortality rate (Singapore, Slovenia and Sweden)?

Answer 2

2-3 out of every 1000 children die before the age of 5

Question 3

What are the three biggest causes of under 5 deaths globally, and what do they have in common?

Answer 3

Pneumonia, malaria and diarrhoea

- all infectious diseases

Question 4

What certain actions can developing countries undertake to reduce under 5 mortality rate?

Answer 4

Vaccines
Clean water - prevent diarrhoea
Oral rehydration therapy
Reduce malnutrition (promote breast feeding and give vitamin A supplements)
Nets - to prevent malaria
Train village health workers to recognise pneumonia

Question 5

What are the most common pathogenic causes of a lower respiratory tract infection in neonates?

Answer 5

Group B strep
E.Coli
Respiratory viruses
Enteroviruses

Question 6

What are the most common pathogenic causes of a lower respiratory tract infection in young infants?

Answer 6

Respiratory viruses
Enteroviruses
Chlamydia

Question 7

What are the most common pathogenic causes of a lower respiratory tract infection in infants and young children?

Answer 7

Strep pneumonia

Respiratory viruses

Question 8

What are the most common pathogenic causes of a lower respiratory tract infection in older children?

Answer 8

Mycoplasma pneumonia.
Strep pneumonia
Respiratory viruses

Question 9

What are the most common pathogenic causes of meningitis in neonates?

Answer 9

Group B strep 
E.Coli
Haemophilus Type B
Meningococcus 
Strep penumonia 
Listeria

Question 10

What are the most common pathogenic causes of meningitis in 1-3 month olds?

Answer 10

Meningococcus
Strep pneumonia
Haemophilus Type B
Listeria

Question 11

What are the most common pathogenic causes of meningitis in 3 month to 5 year olds?

Answer 11

Strep pneumonia
Haemophilus Type B (rare)
Meningococcus

Question 12

What are the most common pathogenic causes of meningitis in children over the age of 6?

Answer 12

Meningococcus

Strep pneumonia

Question 13

Briefly describe how vaccinations (memory) affect antibody-mediated immunity (component of adaptive immunity).

Answer 13

When a B cell encounters an entire that it recognises, the B-cell is stimulated to proliferate and produce large numbers of lymphocytes secreting an antibody to this antigen.
Replication and differentiation of B-cells into plasma cells is regulated by contact with the antigen and by interactions with T cells.

Question 14

Briefly describe cell mediated immunity (component of adaptive immunity).

Answer 14

T cells mediate three principle functions; help, suppression and cytotoxicity.
T-helper cells stimulate the immune response of other cells (Th cells stimulate B-cells to produce antibodies)
T-suppressor cells play an inhibitory role and control the level and quality of the immune response
T-killer cells recognise and destroy infected cells and activate phagocytes to destroy the pathogens they have taken up

Question 15

Describe briefly how vaccines work.

Answer 15

An inactivated or attenuate live sample of the organism is injected into the body.
APCs eat them up, and present the new antigen to the B-cells
The B-cells then reproduce, producing plasma cells, which secrete a specialised antibody for this antigen.
Because the small sample of the organism is safe, the person doesn’t get infected by it. But the B-cell differentiate into memory cells, so that if the disease is ever caught in the future, these memory cells can quickly differentiate into plasma cells, and produce the appropriate antibodies much faster

Question 16

What is the primary response in infection?

Answer 16

The immune response occurring on the first exposure to an antigen
- specific antibodies appearing in the blood after a multiple day latent period

Question 17

What are adjuvants and when are they used?

Answer 17

These are substances that enhance the antibody response, and are used in inactivated vaccines

Question 18

Describe why conjugate vaccines are needed.

Answer 18

Plain polysaccharide antigens do not stimulate the immune system as broadly as protein antigens (such as tetanus, diphtheria or influenza)
- protection from such vaccines are not as long-lasting
- response in infants and young children is poor
Some polysaccharide vaccines have been enhanced by conjugation - - polysaccharide antigen is attached to a protein carrier (like in the Hib and MenC vaccines) giving better immunological memory

Question 19

What is the difference between inactive and live attenuated vaccines?

Answer 19

Live vaccines produce an immune response by growing and replicating in the vaccinated individual over a period of time (days/weeks)
Promotes full, long lasting immunity
- e.g. MMR, VZV, intranasal influenza

Question 20

Why should live attenuate vaccines never be given to immunocompromised individuals?

Answer 20

Although it is a ‘weakened’ version of the disease, some true infections may occur
- this is more likely and more severe in those with an incompetent immune system

Question 21

How does only vaccinating 95% of children eradicate an infection?

Answer 21

They are no longer a source of infection to the unvaccinated - so the cycle of infection is interrupted
- herd immunity

Question 22

What bacteria is the most common cause of bacteraemia and meningitis in children?

Answer 22

Streptococcus penumonia

Question 23

What is the most common presentation of invasive Haemophilus influenza in the under 5s?

Answer 23

Meningitis, frequently accompanied by

• bacteraemia
• epiglottis
• bacteraemia
• pneumonia
• cellulitis

Question 24

How does neisseria meningitidis most commonly present in children?

Answer 24

Meningitis or septicaemia (or a combination of both)

Question 25

In infants (under the age of 1), what factors indicate the severity of the infection?

Answer 25

Feeding/vomiting - decrease in appetite
Crying - crying and not eating
Sleeping - increase in the amount of sleep
Smiling - normally start at around 6 weeks

Question 26

In a child (over the age of 1), what factors indicate the severity of the infection?

Answer 26

Feeding
Activity levels
Drowsiness

Question 27

What localising symptoms are worrying in a possible infected child?

Answer 27

Cough
Coryza
Vomiting 
Diarrhoea 
Rash
Dysuria 
Headache 
Sore ears/throat

Question 28

When children are born, why is the immune system so immature?

Answer 28

In order the maintain the foetus the mother needs to ignore foetal allogenigens (as half of the antigens are parental/foreign).
This means there is an immunosuppressed/regulated environment during pregnancy, and this carries over into early life

Question 29

How does the mother protect the child from pathogens?

Answer 29

Transfer of IgA via the placenta, and then later, via breast milk.
This antibody works at mucosal surfaces, preventing pathogen entry