Comprehensive Guide to the Pathophysiology of Malaria

A mosquito bite delivers the parasite; the liver hides it; then red blood cells become its factory. When an infected female Anopheles mosquito bites you, it injects tiny Plasmodium parasites called sporozoites into your bloodstream. Within about 30 minutes they travel to the liver and settle inside liver cells, where they multiply silently for one to two weeks with no symptoms. Once mature, they burst out as merozoites and invade red blood cells, multiplying inside them until the cells rupture in coordinated waves — this is what produces the classic malaria fever, chills and sweats every 48 or 72 hours. Some parasites turn into sexual forms called gametocytes that the next mosquito can pick up, continuing the cycle.

The cyclic fever comes from parasites bursting out of red blood cells all at once, not from the bite itself. When millions of infected red cells rupture at the same time, they release parasite proteins that trigger a big immune reaction — high fever, shaking chills, sweating, muscle aches and headache. The destruction of red blood cells also drops haemoglobin, causing anaemia, fatigue and pale skin. In Plasmodium falciparum infections, infected red cells stick to the walls of small blood vessels, blocking blood flow in the brain, lungs and kidneys — which is why falciparum malaria can rapidly become life-threatening. Nausea, vomiting, back pain and dark urine (from broken-down red cells) often follow.

Confusion, seizures, extreme weakness, breathlessness and dark or reduced urine mean the malaria has turned severe. Cerebral malaria (mostly from P. falciparum) causes altered consciousness, seizures and coma. Other severe features include very low haemoglobin, respiratory distress, kidney failure (sometimes called blackwater fever from dark urine), dangerously low blood sugar and metabolic acidosis. Children under five, pregnant women, elderly people and anyone with a weakened immune system are at highest risk. Any fever plus one of these signs after a mosquito bite or travel to a malaria area needs emergency hospital care — severe malaria can kill within 24 hours if untreated.

A blood test confirms malaria within minutes, and treatment usually cures it in 3–7 days if started early. Doctors diagnose malaria by looking at a stained blood smear under the microscope — this identifies the species and how many parasites are present. Rapid diagnostic tests (RDTs) give a result in 15–20 minutes from a finger-prick sample and are widely used in clinics and endemic areas. PCR is used in complex or research cases. Treatment depends on the species and severity: uncomplicated cases usually get artemisinin-based combination therapy (ACT) for three days; severe malaria needs intravenous artesunate in hospital plus supportive care. P. vivax and P. ovale also need a drug like primaquine to clear liver-stage parasites and prevent relapse.