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Year 3 - CR > Malaria > Flashcards

Flashcards in Malaria Deck (59)
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What is malaria

Systemic tropical parasitic infection of red blood cells caused by plasmodium spp and transmitted by the female anopheles mosquitos


Name the 5 protozoal species of genus plasmodium and if they cause complicated or uncomplicated malaria

- Plasmodium falciparum (most common, complicated)
- Plasmodium vivax (uncomplicated; relapsing)
- Plasmodium ovale (uncomplicated; relapsing)
- Plasmodium malariae (uncomplicated, doesn’t relapse)
- Plasmodium knowlesi (zoonotic malaria (Macaques); restricted to certain parts in SE Asia


What is the most common type of protozoal species

Plasmodium falciparum (most common, complicated)


Where is plasmodium falciparum from



How does transmission of malaria happen

- Bite of infected female Anopheles mosquito
- congenital - transmission through pregnant mother
- blood transfusion


When does the female anopheles mosquito feed

- Dusk to Dawn


What is the incubation period for malaria

Incubation period: 7-30 days (shorter for P. falciparum, longer for P. malariae)


describe an area of stable transmission of malaria

- Populations continuously exposed to malaria
- High background immunity – mainly adults
- Young children suffer acute illness and high parasite densities
- Epidemics less likely
- sub-Saharan Africa and parts of Oceania


Describe an area of unstable transmission of malaria

- Fluctuating rates of malaria
- Low background immunity
- Both adults and children suffer acute malaria and its complications
- epidemics likely to occur due to sudden increase in mosquito vector densities
- Asia and Latin America


Who suffers in stable transmission areas of malaria

- children - lack of immunity


Who suffers in unstable transmission areas of malaria

Both adults and children suffer acute malaria and its complications as children don't have immunity by the time they are adults


How many countries are endemic from malaria

100 tropical countries and some subtropical regions


Where are the greatest number of deaths from malaria

90% of these deaths were in children in sub-Saharan Africa

Those living in the most economically deprived areas


what is the main risk for acquiring malaria in travellers

Failure to take effective prophylaxis is the main risk for acquiring malaria in tropical travellers


Who has higher risk of complications when getting malaria

Older people (>65 years) have higher rates of complications


who accounts for 65% of all cases of malaria in the UK

People who travelled to visit friends and families account for 65% of all cases of malaria in the UK


What is airport malaria

Airport malaria”: mosquitos stowed away in aircrafts or luggage infect people who haven’t travelled abroad


Describe the lifecycle of malaria in the mosquito

- When a female mosquito bites a human who is infected it is the gametocytes that take up the infected malaria
- the gametocytes are ingested into the mosqutios stomach
- they emerge from the infected blood cells and become gametes
- the male and female gametes fuse and produce a zygote
- the zygotes elongate into ookinetes which move through the stomach wall
- ookinetes develop into oocytes
- the oocysts grow and rupture releasing sporozoites
- the sporozoites migrate to the salivary glands and a ready to be inject into an uncontaminated human and renew the cycle


describe how the malaria transmits and has its lifecycle in human

- female mosquito that is infected bits an uninfected human,

Liver cell phase (2 weeks)
- the sporozoites go to the liver cell and infect the liver cell
-in the liver cell they form schizonts or they can remain dormant
- schizonts are large number of merozoites
- when the liver cell ruptures after about 2 weeks they releases the merozoites into the blood stream

Blood cell phase (2-3 day cycles)
- the merozoites infect red blood cells
- the parasite forms a ring called a trophozoite - this becomes larger and can mutiply
- then becomes a schizont
- once the schizont rupture to release multiple merozoites into the blood stream again this stage is associated with high temperature, body aches, and a big cytokine response

- some red blood cells will develop into gametocytes and this will continue the transmission cycle to other people


do you see schizonts on the bloodstream of someone with malaria

not often but, If you do see schizonts on the blood film that patient may deteriorate as you see more schizonts on the blood stream and more parasite is released
- this is an indication for IV use


What species of plasmodium can cause relapse of malaria

P. vivax and Plasmodium ovale only: some sporozoites enter a dormancy stage “hypnozoites” and may cause relapses weeks, months or years later


all types of malaria cause

intervascular hameolysis


What does the infected erythrocytes adhering to host endothelium cause in P.Falciparum

- Microvascular occlusion
- Metabolic derangement and acidosis
- Intravascular haemolysis


What can a schizont rupture evoke

Microvascular occlusion
Metabolic derangement and acidosis
Intravascular haemolysis


Why does P.Falciparum lead to complicated malaria

- leads to move complicated infection due to cytoadherence of the red blood cells by PfEMP1
- this causes the infected red blood cells to adhere to the endothelium and obstruct them causing
- Microvascular occlusion
- Metabolic derangement and acidosis
- Intravascular haemolysis

this can eventually lead to end organ damage


Why does P.falciparum lead to death

- Higher number of red blood cells infected, leads to greater parasitaemias
- infects red blood cells at all ages of the cell
- cause sequestration
- therefore majority of deaths are due to falciparum malaria


what plasmodium does not really cause death from malaria

Vivax and knowlesi can rarely cause severe and fatal malaria - but far less likely


What is the gold stand for malaria diagnosis

- Light Microscopy
- Parasites may be visualized on both thick and thin blood smears stained with Giemsa stains


What is the difference between thick and thin blood film for light microscopy

Thick blood film:
- sensitive
- allows examination of a greater volume of RBCs
- concentrates parasites as RBCs are lysed

Thin blood film:
- useful for species identification and determination of level of parasitaemia
- less sensitive than thick film


How does a thick blood film work

- Large drop of blood in a small part of the slide
- fixed to the slide
- can see if there is any gimesa stain parasites there
- doenst tell us the species that is present