Malaria

Malaria is an infection caused by the plasmodium parasite. They are protozoa - meaning they are single called organisms. It is spread via the female anopheles mosquitos, however, it may also spread through blood or blood products.

🏘 Epidemiology

96% of malaria cases and deaths are found in Africa. 70% of cases in Africa are found in West Africa.

It is almost always found in non-endemic regions as a result of travel.

Pathophysiology

🦠 There are 5 plasmodium parasites known to cause infection in humans:

1. Plasmodium falciparum - the most severe of them all.
2. Plasmodium vivax
3. Plasmodium ovale
4. Plasmodium malariae
5. Plasmodium knowlesi

There are 2 phases of the malaria life cycle:

1. Exoerythrocytic phase

The exoerythrocytic phase is generally asymptomatic.

Anopheles mosquitoes are drawn to CO2 and the body odour of humans. Once the mosquito latches on, it “bites” the human, injecting a sporozoite into the bloodstream. These sporozoites attack liver hepatocytes and undergo asexual reproduction (schizogony) to form a hepatic schizont.

P. ovale and p. vivax lay dormant in the liver and form hypnozoites. The schizont ruptures and then releases merozoites.

2. Erythrocytic phase

This phase begins with the merozoite being released into the blood and binding to RBC antigens to allow entry into the RBC. It undergoes asexual reproduction within the RBC once again over 48 hours (hence the intermittent fever).

It develops into another 3 phases: merozoite → early trophozoite (ring form) → late trophozoite → erythrocytic schizont.

The erythrocytic schizont undergoes either mitosis (forming merozoites once again) and continuing the cycle as the red blood cells rupture to release these merozoites back into the blood (causing haemolytic anaemia also). Or it could undergo gametogony to form a gametocyte which gets sucked up by another anopheles mosquito to allow for sexual reproduction. This cycle then continues when the mosquito feeds again.

😷 Presentation

Non-specific symptoms:

1. Fever - is intermittent
1. 24-48 hours if falciparum (malignant tertian fever).
2. Every 48 hours if vivax and ovale (tertian fever).
3. 72 hours if malariae (quartan fever).
2. Malaise
3. Myalgia
4. Headache
5. Vomiting

Malaria-specific symptoms:

1. Anaemia with pallor.
2. Hepatosplenomegaly
3. Jaundice due to haemolysis and increased bilirubin as a result.

🔍 Investigations

🔬

Diagnosing malaria:

1. 🏆 Giemsa-stained blood smears - detection of the asexual/sexual form (most common form is the trophozoite). 3 samples sent over 3 consecutive days due to 48 hour cycle of malaria being released into blood from RBCs.
2. Rapid diagnostic test (RDTs) - gives a visible band in the presence of malaria antigen/enzyme after 15 minutes.
3. FBC
1. Thrombocytopenia
2. Anaemia

🧰 Management

🔮 Prophylaxis

Advice should be given to travellers going to locations at higher risk. Mosquito sprays and nets should be used and antimalarial medication is recommended too prophylactically.

Options include:

1. Proguanil and atovaquone (Malarone) - to be given daily 2 days before and continued until 1 week after. Has minimal side effect profile.
2. Mefloquine - once weekly 2-3 weeks before, continued until 4 weeks after being in an endemic area.
1. Adverse effects include: bad dreams.
3. Doxycycline - taken daily 2 days and continued until 4 weeks after being in an endemic area.
1. Adverse effects include: diarrhoea, thrush, rash and sunburn (due to increased UV sensitivity).

🚨 Complications

• Cerebral malaria - seizures, retinopathy, abnormal posturing, headache, encephalopathy, reduced consciousness.
• AKI - due to dehydration and hypovolaemia, but may also be due to acute tubular necrosis.
• Pulmonary oedema - causing ARDS (has 50% mortality rate).
• Hypoglycaemia
• Metabolic acidosis