Infections In Childhood Flashcards
What are the main causes of childhood death in the countries with the worst child mortality rate? (Somalia, Mali and Burkina Faso)
War, poverty and political instability
What are the child mortality rates of the countries with the lowest child mortality rate (Singapore, Slovenia and Sweden)?
2-3 out of every 1000 children die before the age of 5
What are the three biggest causes of under 5 deaths globally, and what do they have in common?
Pneumonia, malaria and diarrhoea
- all infectious diseases
What certain actions can developing countries undertake to reduce under 5 mortality rate?
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
What are the most common pathogenic causes of a lower respiratory tract infection in neonates?
Group B strep
E.Coli
Respiratory viruses
Enteroviruses
What are the most common pathogenic causes of a lower respiratory tract infection in young infants?
Respiratory viruses
Enteroviruses
Chlamydia
What are the most common pathogenic causes of a lower respiratory tract infection in infants and young children?
Strep pneumonia
Respiratory viruses
What are the most common pathogenic causes of a lower respiratory tract infection in older children?
Mycoplasma pneumonia.
Strep pneumonia
Respiratory viruses
What are the most common pathogenic causes of meningitis in neonates?
Group B strep E.Coli Haemophilus Type B Meningococcus Strep penumonia Listeria
What are the most common pathogenic causes of meningitis in 1-3 month olds?
Meningococcus
Strep pneumonia
Haemophilus Type B
Listeria
What are the most common pathogenic causes of meningitis in 3 month to 5 year olds?
Strep pneumonia
Haemophilus Type B (rare)
Meningococcus
What are the most common pathogenic causes of meningitis in children over the age of 6?
Meningococcus
Strep pneumonia
Briefly describe how vaccinations (memory) affect antibody-mediated immunity (component of adaptive immunity).
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.
Briefly describe cell mediated immunity (component of adaptive immunity).
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
Describe briefly how vaccines work.
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
What is the primary response in infection?
The immune response occurring on the first exposure to an antigen
- specific antibodies appearing in the blood after a multiple day latent period
What are adjuvants and when are they used?
These are substances that enhance the antibody response, and are used in inactivated vaccines
Describe why conjugate vaccines are needed.
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
What is the difference between inactive and live attenuated vaccines?
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
Why should live attenuate vaccines never be given to immunocompromised individuals?
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
How does only vaccinating 95% of children eradicate an infection?
They are no longer a source of infection to the unvaccinated - so the cycle of infection is interrupted
- herd immunity
What bacteria is the most common cause of bacteraemia and meningitis in children?
Streptococcus penumonia
What is the most common presentation of invasive Haemophilus influenza in the under 5s?
Meningitis, frequently accompanied by
- bacteraemia
- epiglottis
- bacteraemia
- pneumonia
- cellulitis
How does neisseria meningitidis most commonly present in children?
Meningitis or septicaemia (or a combination of both)
In infants (under the age of 1), what factors indicate the severity of the infection?
Feeding/vomiting - decrease in appetite
Crying - crying and not eating
Sleeping - increase in the amount of sleep
Smiling - normally start at around 6 weeks
In a child (over the age of 1), what factors indicate the severity of the infection?
Feeding
Activity levels
Drowsiness
What localising symptoms are worrying in a possible infected child?
Cough Coryza Vomiting Diarrhoea Rash Dysuria Headache Sore ears/throat
When children are born, why is the immune system so immature?
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
How does the mother protect the child from pathogens?
Transfer of IgA via the placenta, and then later, via breast milk.
This antibody works at mucosal surfaces, preventing pathogen entry
