Malaria

Question 1

What causes malaria?

Answer 1

Malaria is caused by infection of red blood cells by protozoan parasite of the Plasmodium genus.

Question 2

How is malaria spread?

Answer 2

Typically by the female anopheles mosquito.

Question 3

What are the different species of protozoa causing malarial infection?

Answer 3

Plasmodium falciparum - commonest, severe malaria
Plasmodium vivax - 2nd most common (dominant outside Africa)
Plasmodium ovale - causes relapsing infection
Plasmodium malariae - less severe illness
Plasmodium knowlesi - rapidly expanding parasite burden, severe illness

Question 4

What is the pathophysiology of malaria infection?

Answer 4

1. Female anopheles mosquito takes up plasmodium sp. gametocytes from animal/human blood. Remains in their salivary glands until injection of sporozoites into new host.
2. Sporozoites travel to hepatocytes of new host where they undergo mitotic replication and mature (schizonts) and finally cause hepatocyte rupture and release of merozoites which invade red cells.
3. The trophozoites then replicate and mature into schizonts in the red cells until they rupture causing haemolysis and the cycle continues as they invade more red cells. This is the symptomatic/asexual cycle.
4. Merozoites can form gametocytes in the sexual cycle which allows transmission between hosts.

Question 5

How do you define malaria as severe?

Answer 5

WHO classification.
Specific stipulation, but essentially with end organ compromise which requires support.
Common reasons for admission to ITU are seizures/cerebral malaria, renal failure, ARDS

CNS: GCS <11, seizures
Acidosis: BE< -8, Bicarb <15, lactate >5
Hypoglycaemia: <2.2
Anaemia: Hb <70
AKI: Urea >20
CVS: Hypotension, systolic <80
Respiratory: Pulmonary oedema, sats <92%
Liver: Jaundice

Question 6

How should you manage a patient with malaria?

Answer 6

Malaria particularly severe or cerebral has a very high mortality. Prompt antimalarial treatment can bring this down to 10%.
Manage the patient with an ABCDE approach correction and supporting abnormalities as you find them.
Assess severity of malaria and need for organ support.

Specific management includes:

1. Involve a specialist
2. ICU admission for severe infection
3. Monitoring of serum glucose
4. careful fluid balance
5. Antimalarials: Artesunate IV therapy followed by artemisinin-based therapy
6. Low threshold for broad-spectrum ABx.