Tropical Infection

Question 1

What are the 2 main categories of tropical infection?

Answer 1

Resource poor setting i.e. restricted to that setting due to lack of sanitation/infrasctructure/healthcare

Climate related due to unique vectors and high temperatures

Question 2

What are important questions to ask about when someone has returned from travel?

Answer 2

1. When travelled
   Can rule some infections based on relation to incubation period
2. Where travelled i.e. exact location and what were doing
3. Why travelled i.e. work or leisure
   More risky behaviour etc

Question 3

What is the approach to differential diagnosis of tropical infections?

Answer 3

Incubation period

Clinical syndrome

• rash= dengue, HIV, Rickettsua
• Diarrhoea= E. coli, campylobacter, salmonella
• jaundice= viral hepatitis, leptospirosis
• eosinophilia- parasitic infection

Geography

Question 4

What are the key investigations?

Answer 4

Sepsis blood culture

Malaria blood films and malaria antigen test

Viral serology

Influenza swab= PCR test

Question 5

What micro-organism is associated with malaria? What are the 5 different forms in humans?

Answer 5

Protozoa called plasmodium

Falciparum= one associated with sub-Saharan Africa
Vivax
Ovale
Malarie 
Knowlesi

Question 6

Can you develop immunity to malaria?

Answer 6

Yes can develop slight immunity to malaria after repeated infections

Question 7

What is the difference between stable and unstable malaria?

Answer 7

Stable= transmission occurs all year around 
Unstable= transmission doesn’t occur all year round

Question 8

How can the spread of malaria be controlled?

Answer 8

Vector control i.e. mosquitos

Better world wide diagnosis

Effective treatment

Vaccine development

Question 9

How does malaria spread?

Answer 9

Anopheles mosquito acts as vector

Water is important part of anopheles life cycle to enable development of eggs to larva
Eg drainage ditch, swamp etc

Indoor biting at night

Indoor resting after bitten human

Question 10

What are the most effective vector control methods?

Answer 10

Reducing human vector contact by insecticide treated nets

Adult mosquito control by reducing life span i.e. indoor residual spraying

Larval control i.e. larvicide and reduction of breeding sites

Question 11

How does malaria develop after vector has bitten host?

Answer 11

Malaria injected into blood and travels to liver via blood stream

Malaria infects liver cells and replicates asexually to produce pod of malaria seeds i.e. 1 WEEK INCUBATION PERIOD

Liver cells burst after incubation period to release the malaria into blood stream
I.e. BLOOD PHASE= SYMPTOMATIC (RBC infected)

Question 12

When do the symptoms of malaria present and why?

Answer 12

The present after a week incubation period when the malaria seeds infect RBC
I.e. infected RBC undergoes changes so that proteins are presented on surface (nobs) where acts to enable adhesion to endothelial cells to prevent the infected blood cells from moving

Question 13

What is the clinical presentation of uncomplicated malaria?

Answer 13

Fever 
Myalgia 
Headache
Vomiting 
Pallor 
Splenomegaly

Question 14

What complications would lead to case of malaria being classified as severe in children? What is the presentation of these complications?

Answer 14

Cerebral malaria

• impaired consciousness
• reduced GCS
• unable to sit or feed (children)
• seizures

Respiratory distress

• deep breathing
• acidosis

Severe anaemia

Question 15

How do malaria complication differ between children and adults?

Answer 15

Cerebral malaria symptoms main symptoms associated with severe malaria in children

Severe malaria is more systemic in adults effecting multiple organ systems

Question 16

How does severe malaria present in adults?

Answer 16

Impaired consciousness 
Renal impairment 
Acidosis
Hypoglycaemia 
Pulmonary oedema or ARDS
Low haemoglobin 
Spontaneous bleeding and intravascular coagulation 
Shock 
Haemoglobinuria

Question 17

Why does pregnancy enable malaria infection in someone who might have immunity? What are the consequences of malaria infection in pregnancy?

Answer 17

Placenta provides niche for infection due to the presence of different proteins in the vessels of placenta meaning malaria is able to adhere to the walls of BV in the placenta

Poor intra-uterine growth
Anaemic babies
Babies with increased risk for infection due to poor immune system

Question 18

How is malaria diagnosed?

Answer 18

Light microscopy of blood films

• thick= looking through layers of blood
• thin= 1 layer of cell but only small amount of blood

Rapid diagnostic tests of plasmodium proteins

PCR for plasmodium genes (used in research)

Question 19

What is parasitaemia and what level indicates serious malaria infection?

Answer 19

Parasitaemia = how many cells out of 100 are infected

> 2%

Question 20

How can malaria be treated? How does this differ between complicated and uncomplicated malaria?

Answer 20

ACT (artemether combination therapy)

Uncomplicated P. Falciparum:
Artemether combined with approved second agent i..e needs to be used in combination with another agent

Complicated:
IV artesunate where possible

Question 21

How has the epidemiology of malaria changed after more prevention strategies have been put into place?

Answer 21

Decreased level of immunity in adult population due to decreased exposure in childhood to malaria infection

Lead to resurgence of malaria

Question 22

How is the presentation of dengue different to malaria?

Answer 22

Dengue has shorter incubation period meaning symptoms present w/i 1 day

Symptoms:

• fever
• headache
• retro-orbital pain
• back ache
• rash
• myalgia
• blanching erythema
• petechial rash (small clusters of round red spots)

Question 23

How is dengue fever diagnosed?

Answer 23

Clinically by location of travel

Can be confirmed by serology or PCR

Question 24

What are the consequences of repeated infections of dengue fever?

Answer 24

haemorrhagic form develops where blood vessels leak

Associated with people who live in areas where dengue is endemic rather than travellers

Question 25

How might someone with typhoid present?

Answer 25

Fever
Weakness
Headache 
No localising signs 
Recent travel to India 
Negative malaria film

Question 26

What microorganism is associated with typhoid? How does it appear on a blood culture?

Answer 26

Salmonella enterica= associated with poor sanitation and contaminated food

Gram -ve rods

Question 27

What are the control measures for typhoid?

Answer 27

Vaccination= only effective for typhi serotype and not widely available

Question 28

What drug is given in the uk to people with typhoid and what are the consequences of this?

Answer 28

Ciprofloxacin= concentrates inside cells which means it can effectively target salmonella typhi which occurs cells

Widespread resistance to drug meaning some typhoid infections cannot be treated using antibiotics any more

Question 29

What are 3 of the more common tropical Protozoa infections? What effect do they have?

Answer 29

Leishmaniasis:
-due to being bitten by sand flies

African Trypanosomiasis

• associated with sub-Saharan African
• known as sleeping sickness

South American trypanosomiasis
-Protozoa which can eat away at cardiac and GIT muscles leading cardiac failure and gut motility problems

Question 30

What is schistosomiasis and what is the consequence of infection?

Answer 30

Water-dwelling worms which can enter through the skin and infect veins i.e. different types will colonise different organ veins
Eggs released causes granulomatous reaction
Chronically this can lead to blood carriers/cirrhosis/haematuria/eosinophilia

Question 31

Where does filariasis infect and what is the consequence of infection?

Answer 31

Worms infect BV and lymphatic which leads to lymphadoema

I.e. lymphodema causes skin break down which leads to chronic skin infections

Question 32

What microorganism can be associated with epilepsy and why?

Answer 32

Pig tap worms

Dysfunctional in lifecycle leads to larva infecting human brain and forming cyst which leads to epilepsy