When do malaria symptoms actually begin to show, leading to the realisation that one might have malaria?  After multiplying silently in the liver, Plasmodium parasites, which are now called merozoites, burst out of the liver cells and enter the bloodstream, or rather specifically they enter the red blood cells. It is here, inside red blood cells, that the parasite triggers the symptoms we recognise as malaria, namely fever, chills, fatigue, and sometimes anaemia.

Red blood cells, the parasite’s playground

Merozoites are highly specialised for life inside red blood cells. Once they attach, they to the blood cells, they enter the cells and begin a new cycle of growth and multiplication. Inside each red blood cell, the parasite progresses through distinct stages:

• Ring stage: The parasite first appears as a tiny ring-shaped structure inside the cell.
• Trophozoite stage: It grows larger, feeding on haemoglobin and preparing to divide.
• Schizont stage: The parasite divides to produce dozens of new merozoites.

Finally, the red blood cell bursts, releasing the new parasites into the bloodstream, ready to infect more red blood cells. This cycle repeats every 48 to 72 hours, depending on the parasite species.

Symptoms emerge

The destruction of red blood cells is what causes malaria’s trademark symptoms. Fever and chills coincide with the synchronised bursting of many red blood cells. The breakdown of haemoglobin can lead to anaemia, and the accumulation of waste products in the blood contributes to fatigue, headache, and general malaise. Other symptoms can also include , nausea, minimal vomiting, muscular pains, slight diarrhoea and slight increase of body temperature. Symptoms are often mistaken for influenza or gastro-intestinal infection, or a bad flu.

Because this process occurs in cycles, malaria often comes with bouts of fever, which are basically periods of high temperature followed by relative calm, thus reflecting the life cycle of the parasite inside the blood.

During the blood stage, while most of the merozoites continue asexual multiplication, a small fraction of the merozoites develop into gametocytes, the sexual forms essential for transmission of the parasite to mosquitoes, and ultimately for the parasite to continue its life cycle.

Why the blood stage is critical

The blood stage is; therefore, not only responsible for illness but also for transmission of the malaria disease. Stopping the parasite during the blood stage with antimalarial drugs can save lives and prevent further spread, making this phase a central target for treatment and control strategies. Blood-stage parasites can be effectively targeted with antimalarial drugs, particularly artemisinin-based combination therapies (ACTs), which kill merozoites inside red blood cells and reduce gametocyte formation. Prompt diagnosis and treatment not only relieve symptoms and prevent complications but also limit the number of parasites available for mosquitoes to pick up, interrupting the transmission cycle.

In the next article, we examine how Plasmodium falciparum can cause life-threatening complications, particularly in children and pregnant women, and why early diagnosis and treatment are so critical.

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