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Year 3 - CR > Malaria > Flashcards

Malaria Flashcards

1
Q

What is malaria

A

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

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2
Q

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

A
  • 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
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3
Q

What is the most common type of protozoal species

A

Plasmodium falciparum (most common, complicated)

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4
Q

Where is plasmodium falciparum from

A

africa

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5
Q

How does transmission of malaria happen

A
  • Bite of infected female Anopheles mosquito
  • congenital - transmission through pregnant mother
  • blood transfusion
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6
Q

When does the female anopheles mosquito feed

A
  • Dusk to Dawn
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7
Q

What is the incubation period for malaria

A

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

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8
Q

describe an area of stable transmission of malaria

A
  • 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
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9
Q

Describe an area of unstable transmission of malaria

A
  • 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
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10
Q

Who suffers in stable transmission areas of malaria

A
  • children - lack of immunity
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11
Q

Who suffers in unstable transmission areas of malaria

A

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

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12
Q

How many countries are endemic from malaria

A

100 tropical countries and some subtropical regions

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13
Q

Where are the greatest number of deaths from malaria

A

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

Those living in the most economically deprived areas

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14
Q

what is the main risk for acquiring malaria in travellers

A

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

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15
Q

Who has higher risk of complications when getting malaria

A

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

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16
Q

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

A

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

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17
Q

What is airport malaria

A

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

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18
Q

Describe the lifecycle of malaria in the mosquito

A
  • 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
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19
Q

describe how the malaria transmits and has its lifecycle in human

A
  • 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
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20
Q

do you see schizonts on the bloodstream of someone with malaria

A

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

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21
Q

What species of plasmodium can cause relapse of malaria

A

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

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22
Q

all types of malaria cause

A

intervascular hameolysis

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23
Q

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

A
  • Microvascular occlusion
  • Metabolic derangement and acidosis
  • Intravascular haemolysis
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24
Q

What can a schizont rupture evoke

A

Microvascular occlusion
Metabolic derangement and acidosis
Intravascular haemolysis

25
Q

Why does P.Falciparum lead to complicated malaria

A
  • 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

26
Q

Why does P.falciparum lead to death

A
  • 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
27
Q

what plasmodium does not really cause death from malaria

A

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

28
Q

What is the gold stand for malaria diagnosis

A
  • Light Microscopy

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

29
Q

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

A

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
30
Q

How does a thick blood film work

A
  • 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
31
Q

How do you identify a specieis of malaria from a blood film

A

Thin blood film

32
Q

How does a thin blood film work

A
  • Spread thinly out over a larger area and see the morphology - smaller number of parasites
33
Q

Describe what P.falciparum looks like on a blood film

A
  • Numerous fine ring forms.
  • Double chromatin dots
  • Multiple parasitization of cells
  • Schizonts rare in peripheral blood
  • Red cells are not enlarged
34
Q

What does P.Vivax look like on a blood film

A
  • Developing and thick (signet) ring forms
  • Trophozoites have an amoeboid appearance
  • Enlarged red cells
35
Q

Describe what P. Ovale looks like on a blood film

A
  • Oval-shaped trophozoite
  • Comet-like red cells.
  • Enlarged red cells
36
Q

Describe what P.Malariae looks like on a blood film

A
  • Broad band form of plasmodium.

- Red cells not enlarged.

37
Q

Describe what P.Knowlesi look like

A
  • Ring stages resemble P. falciparum
  • Mature stages indistinguishable from P. malariae
  • Molecular methods needed to confirm diagnosis
38
Q

name another way to diagnose malaria

A

Antigen detection

39
Q

What antigens are used to diagnose malaria

A
  • detection of an antigen (histidine rich protein-2, HRP-2) associated with P. falciparum
  • detection of a plasmodium-associated lactate dehydrogenase (pLDH)
40
Q

Name the antigen associated with P. falciparum

A

histidine rich protein-2, HRP-2

41
Q

Describe how antigen detection works

A

Detection of antigens or enzymatic activities associated with the malaria parasites

Methods are often packaged as individual test kits called rapid diagnostic tests or RDTs

42
Q

What is the clinical presentation of malaria

A
  • Fever (temperature may be normal at the time of assessment)
  • Headache,
  • muscle aches,
  • diarrhoea
  • vomiting
  • cough and SOB if pulmonary oedema
  • seizures
  • changes in the urine if renal involvement
43
Q

what should you look for in a foreign history

A
  • When: last 12 month for falciparum (longer for other types of malaria)
  • Where: likely risk of malaria, Plasmodium spp, resistance, etc
  • Malaria prophylaxis (drugs, duration, compliance)
44
Q

What prediposes you to more severe malaria

A

Pregnancy status (high risk for complications)

Immunocompetence status (HIV, cancer, transplant recipients)

45
Q

Describe how you should examine a patient with malaria

A 
A - airway 
B - breathing 
C - circulation 
D - disability 
E - exposure 
F- fluids 
G - glucose
46
Q

What are the signs of severe malaria

A
  • Impaired consciousness or seizures.
  • Renal impairment (oliguria <0.4 ml/kg bodyweight per hour or creatinine >265 mmol/l)
  • Acidosis (pH < 7.3)
  • Hypoglycemia (<2.2 mmol/l)
  • Pulmonary oedema or acute respiratory distress syndrome (ARDS)
  • Haemoglobin less than 80 g/L
  • Spontaneous bleeding/disseminated intravascular coagulation
  • Shock
  • Haemoglobinuria (without G6PD deficiency)
  • Parasitaemia >10%
47
Q

What severe signs of malaria are more common in children

A
  • Severe anaemia
  • hypoglycaemia
  • seizures
48
Q

What severe signs of malaria are more common in adults

A
  • renal failure

- parasite count greater than 2%

49
Q

Name a sign of severe malaria

A

severe opisthotonic (extensor) posturing

50
Q

How do you manage severe malaria

A
  • Seek expert advice
  • Anti-pyretic therapy as appropriate
  • Careful rehydration if indicated (risk of pulmonary oedema)
  • Other supportive measures as appropriate
  • May require nursing on HDU/ITU ward
  • Non-falciparum malaria cases may be managed in outpatients
  • Notify your local Public Health Team
51
Q

What is the drug treatment for uncomplicated P.falciparum

A

Oral therapy with either

  • Malarone (Atovaquone-Proguanil)
  • Riamet (Artemether-lumefantrine; artemesinin combination therapy – ACT)
  • Quinine & Doxy / Clinda
52
Q

What is the drug treatment for non facliparum malaria

A

Chloroquine followed by primaquine - check G6PD status (primaquine can lead to haemolysis if G6PD deficient)

53
Q

How do you treat severe and complicated P.Falciparum

A
  • IV Artesunate (preferred) OR
  • IV Quinine (cardiac & blood glucose monitoring)
  • Oral therapy as for uncomplicated once improved
  • check blood film daily
54
Q

What is indications for IV therapy

A
  • Parasitaemia >2% or presence of schizonts
  • Vomiting
  • Pregnancy (get specialist advice)
55
Q

How do you prevent malaria

A

A - awareness of the risk
B - bite prevention
C - chemoprophylaxis
D - prompt Diagnosis and treatment

56
Q

What personal protective measures can you use

A

DEET-based insect repellents

Bed nets: Insecticide-treated nets

Clothing

57
Q

What chemoprophylaxis can you use for malaria

A

Travel clinics

Follow evidence-based guidelines

Different regimes for different countries depending on malaria species + anti-malarial resistance patterns

No regime is 100% protective: need to use a combination of protective measures

58
Q

describe what vector control you can have to prevent malaria

A

Insecticide-treated nets (ITNs)

  • Effective public health intervention for communities suffering malaria
  • Issues around cost, logistics, and insecticide resistance
  • Long-term effects on background population immunity

Indoor residual spray (IRS)

59
Q

How long does the fever last with each malaria type

A
  • 24hrs – P. knowlesi
  • 48hrs – P. vivax/ovale/falciparum
  • 72hrs – P. malariae

Year 3 - CR (44 decks)

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