Tropical Infection Flashcards
What are the 2 main categories of tropical infection?
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
What are important questions to ask about when someone has returned from travel?
- When travelled
Can rule some infections based on relation to incubation period - Where travelled i.e. exact location and what were doing
- Why travelled i.e. work or leisure
More risky behaviour etc
What is the approach to differential diagnosis of tropical infections?
Incubation period
Clinical syndrome
- rash= dengue, HIV, Rickettsua
- Diarrhoea= E. coli, campylobacter, salmonella
- jaundice= viral hepatitis, leptospirosis
- eosinophilia- parasitic infection
Geography
What are the key investigations?
Sepsis blood culture
Malaria blood films and malaria antigen test
Viral serology
Influenza swab= PCR test
What micro-organism is associated with malaria? What are the 5 different forms in humans?
Protozoa called plasmodium
Falciparum= one associated with sub-Saharan Africa Vivax Ovale Malarie Knowlesi
Can you develop immunity to malaria?
Yes can develop slight immunity to malaria after repeated infections
What is the difference between stable and unstable malaria?
Stable= transmission occurs all year around Unstable= transmission doesn’t occur all year round
How can the spread of malaria be controlled?
Vector control i.e. mosquitos
Better world wide diagnosis
Effective treatment
Vaccine development
How does malaria spread?
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
What are the most effective vector control methods?
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
How does malaria develop after vector has bitten host?
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)
When do the symptoms of malaria present and why?
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
What is the clinical presentation of uncomplicated malaria?
Fever Myalgia Headache Vomiting Pallor Splenomegaly
What complications would lead to case of malaria being classified as severe in children? What is the presentation of these complications?
Cerebral malaria
- impaired consciousness
- reduced GCS
- unable to sit or feed (children)
- seizures
Respiratory distress
- deep breathing
- acidosis
Severe anaemia
How do malaria complication differ between children and adults?
Cerebral malaria symptoms main symptoms associated with severe malaria in children
Severe malaria is more systemic in adults effecting multiple organ systems
How does severe malaria present in adults?
Impaired consciousness Renal impairment Acidosis Hypoglycaemia Pulmonary oedema or ARDS Low haemoglobin Spontaneous bleeding and intravascular coagulation Shock Haemoglobinuria
Why does pregnancy enable malaria infection in someone who might have immunity? What are the consequences of malaria infection in pregnancy?
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
How is malaria diagnosed?
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)
What is parasitaemia and what level indicates serious malaria infection?
Parasitaemia = how many cells out of 100 are infected
> 2%
How can malaria be treated? How does this differ between complicated and uncomplicated malaria?
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
How has the epidemiology of malaria changed after more prevention strategies have been put into place?
Decreased level of immunity in adult population due to decreased exposure in childhood to malaria infection
Lead to resurgence of malaria
How is the presentation of dengue different to malaria?
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)
How is dengue fever diagnosed?
Clinically by location of travel
Can be confirmed by serology or PCR
What are the consequences of repeated infections of dengue fever?
haemorrhagic form develops where blood vessels leak
Associated with people who live in areas where dengue is endemic rather than travellers
How might someone with typhoid present?
Fever Weakness Headache No localising signs Recent travel to India Negative malaria film
What microorganism is associated with typhoid? How does it appear on a blood culture?
Salmonella enterica= associated with poor sanitation and contaminated food
Gram -ve rods
What are the control measures for typhoid?
Vaccination= only effective for typhi serotype and not widely available
What drug is given in the uk to people with typhoid and what are the consequences of this?
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
What are 3 of the more common tropical Protozoa infections? What effect do they have?
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
What is schistosomiasis and what is the consequence of infection?
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
Where does filariasis infect and what is the consequence of infection?
Worms infect BV and lymphatic which leads to lymphadoema
I.e. lymphodema causes skin break down which leads to chronic skin infections
What microorganism can be associated with epilepsy and why?
Pig tap worms
Dysfunctional in lifecycle leads to larva infecting human brain and forming cyst which leads to epilepsy
