Malaria - pathophysiology, prophylaxis, treatment, types of immunity

What is malaria?

It is a potentially fatal tropical disease called by Plasmodium parasites.

What is the vector for malaria?

The female Anopheles mosquito.

Which plasmodium species causes the most severe malarial disease?

Plasmodium falciparum: Causes Falciparum malaria/malignant tertian malaria (most severe

form). Irregular fever spikes

What are other plasmodium species causing malaria?

• Plasmodium vivax:

• Plasmodium ovale:

• Plasmodium malariae:

• Plasmodium knowlesi:

What kind or organism are protozoa?

Unicellular eukaryotes

What are the stages of plasmodium lifecycle in malaria?

1. hepatic stage

2. erythrocytic stage

3. gametocyte formation & transmission

What happens during the hepatic stage?

• Hepatocytes invades by sporozoites, which undergo a phase of asexual reproduction

• Mature merozoites are released from hepatocytes into bloodstream = parasitaemia

What happens during the erythrocytic stage?

• Merozoites rapidly invade RBCs

• Undergo sequential developmental stages

• Each infected RBC ultimately ruptures, releasing new merozoites - perpetuating the infectious cycle

• Repeated RBC infection & lysis = characteristic clinical manifestation of malaria (fever, anaemia, systemic inflammation)

What happens during gametocyte formation and transmission?

• During each cycle of asexual blood-stage replication, a subset of parasites differentiates into sexual forms called gametocytes

• These gametocytes are essential for transmitting malaria.

• If another female anopheles mosquito feeds on the infected individual, circulating gametocytes are infected - these can be passed on to another host.

What is responsible for the main clinical manifestations of malaria?

Due to repeated cycles of haemolysis of infected erythrocytes and the subsequent inflammatory response.

General symptoms of malaria?

• Flu like symptoms

• Diaphoresis (excessive sweating)

• high fever

• periodic fever spikes

Blood specific symptoms?

• thrombocytopenia

• haemolytic anaemia

GI symptoms?

• nausea, vomiting

• Diarrhoea

• abdominal pain

Liver symptoms?

• hepatomegaly

• discreet pre hepatic jaundice

What are the manifestations of severe malaria?

• Kidneys: Flank pain, oliguria (reduced urine output), haemoglobinuria (free Hb in urine)

• Cerebral: Hallucinations, confusion, impaired consciousness, or even coma

• Cardiopulmonary: Heart failure, pulmonary oedema, shock

What causes severe organ dysfunction in malaria?

Infected RBCs occlude capillaries

Malaria prophylaxis: in areas where P.faliparum is present, which drug should be used?

Chloroquine

• If chloroquine resistant use: Atovaquone – proguanil, doxycycline, mefloquine

Malaria prophylaxis: in areas without P.falciparum, what drug should be used?

Primaquine

How long after leaving the area should prophylaxis be continued for?

4 Weeks

How long before departure should malaria prophylaxis be taken?

• chloroquine = 1 week before

• melfoquine = 2-3 weeks before