Malaria

Question 1

What is malaria?

Answer 1

Infection with protozoan Plasmodium.

Question 2

What is the aetiology of malaria?

Answer 2

Transmitted by bite of the female Anopheles mosquito. Rarely through transplantation/infusion.

Question 3

What are the Plasmodium organisms that cause malaria? (x5)

Answer 3

Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, Plasmodium knowlesi.

Question 4

What is the pathophysiology of malaria?

Answer 4

1. Sporozoites (motile spore-like stage in the life cycle of some sporozoans) are injected into the blood stream
2. Invasion and replication in hepatocytes (at this point, the protozoa is called exoerythrocytic schizogeny). P. vivax and P. ovale may develop into dormant hypnozoites and cause relapse within months or years.
3. Protozoa may re-enter the circulation (now called merozoites) and invade RBCs where they develop into TROPHOZOITES in a process called erythrocytic schizogeny
4. The RBCs rupture and release more merozoites which reinfect new RBCs. The rupture releases toxins which result in cytokine release from macrophage and manifestation of symptoms
5. Some merozoites differentiate into larger forms inside RBCs – male and female gametocytes (instead of rupturing the RBC) – which are taken up by the Anopheles mosquitoes, and develop sporozoites in their gut which migrate to the salivary gland for re-transmission

Question 5

What is the epidemiology of malaria: Type? Where?

Answer 5

Plasmodium falciparum is the most deadly, and is also the most common cause of disease. Endemic in tropics.

Question 6

What populations have innate immunity to malaria? (x4)

Answer 6

Sickle cell trait, G6PD deficiency, pyruvate kinase deficiency, thalassaemia.

Question 7

What are the signs and symptoms of malaria?

Answer 7

• Cyclical symptoms of high fever, flu, severe sweating and shivering.
• Peak temperature may coincide with rupture of intra-erythrocytic schizonts: every 48 hours for P. falciparum (called malignant tertian because occurs every third day), vivax and ovale (called benign tertian), 72 hours for P. malariae (called benign quartan because occurs every fourth day)
• Anaemia
• Hepatosplenomegaly
• Cerebral malaria (complication): headache, disorientation, coma

Question 8

What are the investigations for malaria? (x5)

Answer 8

• GIEMSA-STAINED THICK AND THIN BLOOD FILM: preferred test; has to be negative for three days to exclude malaria. See photo.
• FBC: thrombocytopenia (rarely with bleeding abnormalities) and anaemia
• LFTs: show raised bilirubin and aminotransferases
• URINALYSIS: protein or blood if severe
• ABG: acidic if severe