Malaria Flashcards
Describe the malaria life cycle (9)
- Mosquito transmission
- Anopheles female bites human and injects sporozoites into the bloodstream - Liver stage
- Sporozoites go to the liver to invade the hepatocytes
- Sporozoites multiply asexually in hepatocytes –> hypnozoites –> schizont - Hepatocyte rupture
- Mature liver schizont releases merozoites into the blood stream - Erythrocyte cell stage
- Merozoites invade the red blood cells
- In the erythrocyte they mature to schizonts
- These burst and release more merozoites (fever + unwell stage) - Sexual stage
- Some merozoites develop into the sexual forms called gametocytes - Mosquito uptake
- New mosquito bites and ingests the gametocytes - Mosquito midgut
- In the midgut the gametocytes devlop into gametes which fuse to form a zygote - Oocyst formation
- The oocyst lodges onto the gut wall which then produces lots of sporozoites - Sporozoite migration
- Migrate to the salivary glands ready for the next bloodmeal
Which species of malaria can stay dormant in the liver?
P vivax and P ovale
What is a var gene in malaria?
PfEMP1 is an example of the multiple var genes
These help malaria to evade the immune system by sticking to the walls of blood vessels and avoiding being cleared away by the spleen
What are the 4 main principles of malaria control?
- Vector control
- Bite prevention
- Chemoprophylaxis/vaccination to prevent infection
- Active case finding to prevent onward transmission
Which antimalarial drug targets the gametocyte stage?
Primaquine
Which species of malaria might relapse and how do you treat it?
P vivax and ovale
Primaquine - except avoid in G6PD deficiency, pregnancy, infants, breastfeeding
Which malaria species rare, commonly seen in Malaysia which can present with severe disease?
P knowlesi
Malaria - diagnostics
Thick and thin blood smears
RDT
Lab:
Anaemia
Hypoglycaemia
Thrombocytopenia
Lactic acidosis
Jaundice
AKI
Renal failure
Malaria treatment in severe and non-severe
Severe:
IV artesunate
Careful fluid balance and glucose management
Broad spectrum antibiotics (e.g. ceftriaxone)
Non-severe:
Artemisinin combination therapies (ACT)
IV artesunate considerations?
Needs follow up for delayed haemolysis
How do you manage treatment failure in malaria?
<28 days
Recommended 2nd line treatment is an alternative ACT
> 28 days
Consider as a new infection & treat with first line ACT
What are some complications of malaria?
Cerebral malaria - impaired consciousness, retinopathy, seizures, cerebral odoema and raised ICP
Severe anaemia - especially in young children and pregnant women
ARDS
Hypoglycaemia
Lactic acidosis
Shock
Challenges to malaria control strategies (7)
- Sustainable financing
- Drug resistance
- Insecticide resistance including behavioural resistance
- Diagnostics
- Lack of community engagement
- Climate change e.g. Anopheles stephensi in Asia very efficient in urban settings coming to Africa, affecting vector distribution and reproduction
- National priority shifting
- Movement population
Malaria chemoprevention strategies (4)
Intermittent preventive treatment of malaria in pregnancy (IPTp):
3 doses given during pregnancy at antenatal visits
Perennial malaria chemoprevention (PMC)
Given to children in endemic areas with seasonal transmission during the usual vaccination program
Intermittent preventive treatment of malaria in school aged children (IPTsc)
Given to children aged 5-15 during school time
Post-discharge malaria chemoprevention (PDMC)
Prevention in the recovery period to allow them to recover from the complications like anaemia
Are there malaria vaccines available?
Yes - RTS and R21
May be helpful in combination with other measures before high transmission seasons
