Malaria Overview and Life Cycle

Study Notes

Malaria disease is caused by a parasite belonging to the Plasmodium genus.
Four types of Plasmodium infect humans: P. vivax, P. falciparum, P. malariae, and P. ovale.
P. vivax causes benign tertian malaria.
P. falciparum causes malignant tertian malaria.
P. malariae causes quartan malaria.
P. ovale causes oval tertian malaria.
Malaria has a complex life cycle that takes place in two hosts: humans and female Anopheles mosquitoes.

In humans, the Plasmodium parasite undergoes an asexual cycle.
The first stage of the asexual cycle occurs in the liver (exoerythrocytic schizogony)
The second stage of the asexual cycle occurs in red blood cells (erythrocytic schizogony).

In the female Anopheles mosquito, the Plasmodium parasite undergoes a sexual cycle.
The mosquito takes up gametocytes from infected humans during a blood meal.
In the mosquito’s gut, gametes form zygotes.
Zygotes develop into ookinetes, sporozoites, and sporozoites migrate to the mosquito’s salivary glands.
Plasmodium parasites are transmitted to humans through the mosquito’s saliva during a blood meal.

The "gold standard" test for malaria diagnosis is microscopic identification of Plasmodium parasites in blood samples.
Quantitative Buffy Coat (QBC) analyzes the parasites in the buffy coat after centrifugation of blood.
Immunechromatographic technique (ICT) detects Plasmodium specific antigens in patient blood.

Anti-malarial drugs are used to treat malaria.
Supportive therapy such as bed rest, cold sponging, antipyretics, and sedatives for headaches is also provided.
The World Health Organization (WHO) recommends artemisinin-based combination therapy (ACT) for treatment of malaria.

Relapse occurs when dormant hypnozoites in the liver reactivate and release merozoites that infect red blood cells. Relapse occurs in P. vivax and P. ovale infections.
Recrudescence occurs when blood stage parasites survive treatment and reactivate, resulting in a recurrence of symptoms. It can occur in all Plasmodium species but mainly in P. falciparum and P. malariae.
Reinfection can occur when an individual is bitten by an infected mosquito after a previous infection has been treated. In endemic areas, reinfection often results in mild symptoms due to the development of partial immunity.