Travel Related Infections

Question 0

Describe Malaria and its pathogenesis

Answer 0

Parasitic protozoa - plasmodium falciparum, ovale, malariae
Spread - vector (female Anopheles mosquito bites infected person –> gut –> blood –> saliva –> bites uninfected person –> blood –> liver –> blood)
Occurs in the trophics
Inoculation period - 1-3 weeks or months
First a non-specific malaise, then fever/sweats cycle
Detect by blood smear to detect parasites
Treatment with quinine/primaquine
Prevention - Assess risk, Bite prevention, Chemoprophylaxis

Question 1

Understand the importance of a travel history

Answer 1

Where?
When? 
How? Direct/via
Accommodation?
How long? 
Who with?
What did you do? Specific risks including sexual contact 
Were any animals involved? 
Preventative measures

Question 2

Describe Enteric Fever, including its assessment and management

Answer 2

Salmonella enterica bacteria, typhi/Paratyphi strain, gram -ve bacilli
Spread - foecal-oral route via contaminated food/water, endotoxin
Widespread distribution - areas of poor sanitation
Incubation period - 7-14 days
Symptoms/signs - moderate anaemia, raised LFTs, hepatosplenomegaly, rash, bradycardia, haemorrhag
Culture - blood/faeces to recover organism
Treatment - ceftriaxone
Prevention - typhoid vaccine

Question 3

Describe Influenza virus and its transmission

Answer 3

Virus - ss RNA
Spread - airborne, manure
Transmission - contaminated animal feed, water, equipment etc.
Subtypes - haemagglutinin (H), neuraminidase (N) e.g. H1N1
Symptoms - fever, cough, myalgia, pneumonia
Prevention - vaccine (for immunocompromised, extremes of age, asthmatics etc.)

Question 4

Describe Legionella pneumophilia and an example of its clinical importance

Answer 4

G-ve coccobacillus, aerobic, non spore forming
Invades macrophages, surrounds itself with a vacuole and multiplies
Found in aquatic systems
Spread - vomiting, inhalation of aerosolised contaminated water/soil, faulty air conditioning
Causes bibasal pneumonia with consolidation
Treat - macrolide/fluoroquinolones/tetracycline

Question 5

Describe features of antigen presenting cells

Answer 5

Strategic location - skin, mucous membranes, lymphoid organs, blood circulation
Pathogen capture - phagocytosis, micropinocytosis
Diversity in pathogen sensors - extracellular (bacteria) –> humoral, intracellular (viruses) –> cell dependent

Question 6

Describe MHC molecules in relation to microbe presentation

Answer 6

MHC Class I - found on all nucleated cells, present peptides for intracellular microbes –> CD8+ T cells (healthy cells ignored, foreign cells attacked)
MHC Class II - found on antigen presenting cells, present peptides for all extracellular microbes –> CD4+ T cells

Question 7

Describe T cells and their role with regard to infection

Answer 7

T cells mature in the thymus
They can produce memory cells
CD8+ T cells protect against intracellular pathogens
CD4+ T cells help the immune response (CD8+ –> cytotoxic T –> death)
Decreased CD4+ = increased viral load (HIV)

Question 8

Describe B cells and antibody production with regard to infection

Answer 8

CD4+ T cells activate B cells

Antibodies opsonise, neutralise and activate complement