Malaria
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Direct answer
Malaria is caused by protozoan parasites of the genus Plasmodium — mainly Plasmodium vivax, P. malariae, P. falciparum and P. ovale — which have a digenetic life cycle completing part of it in humans and part in the female Anopheles mosquito, the vector. Sporozoites injected with the mosquito's saliva multiply first in liver cells and then in red blood cells; when the infected red cells rupture, the released toxin haemozoin causes the classic attack of shaking chills and high fever recurring every three to four days. Falciparum malaria is the malignant, potentially fatal form.
What you must remember
- Causative organisms: four Plasmodium species infect humans — P. vivax (the most common), P. malariae, P. falciparum and P. ovale.
- Vector: the female Anopheles mosquito, which transmits the parasite while taking a blood meal; the parasite's life cycle is digenetic, requiring both the human and the mosquito hosts.
- Inoculation: sporozoites enter the human bloodstream with the mosquito's saliva and reach the liver, where they multiply; the parasite then infects red blood cells.
- Fever mechanism: rupture of infected red blood cells releases haemozoin, a substance responsible for the periodic chill-and-fever paroxysm.
- Periodicity: the fever recurs every three to four days in patterns characteristic of the infecting species.
- Malignant malaria: Plasmodium falciparum causes the most dangerous, sometimes fatal malaria if not treated promptly.
- Control: preventing mosquito breeding, using nets and repellents, and early diagnosis and treatment under medical supervision, the pillars of India's national anti-malaria programmes.
Common confusion
The fever of malaria is periodic with chills, unlike the sustained fever of typhoid — a favourite discrimination in MCQs. Students also mix the two hosts: the female Anopheles is the vector, not the cause, and the parasite's sexual phase occurs in the mosquito while asexual multiplication occurs in the human. Note that only the female mosquito transmits malaria, because she alone takes blood meals required for egg development.
Exam-focused takeaway
NEET-UG asks the Plasmodium species by name, the vector and its sex, the digenetic nature of the life cycle, and the role of haemozoin in fever. Match-the-following rows pair malaria with protozoa and the Anopheles vector, statement items contrast malarial periodic fever with typhoid's sustained fever, and P. falciparum's reputation as malignant malaria is tested repeatedly.
Frequently asked questions
Which parasites cause human malaria?
Plasmodium vivax, Plasmodium malariae, Plasmodium falciparum and Plasmodium ovale, of which P. falciparum causes the most severe disease.
How does the malarial parasite reach humans?
Through the bite of the female Anopheles mosquito, which injects sporozoites with its saliva while taking a blood meal.
Why do malarial fevers recur periodically?
Because red blood cells rupture in synchrony, releasing haemozoin, the toxin that triggers bouts of chills and high fever every three to four days.
Why is the life cycle of Plasmodium called digenetic?
It requires two hosts — the human, in whom asexual multiplication occurs, and the female Anopheles mosquito, in which the sexual cycle is completed.
What makes falciparum malaria dangerous?
Plasmodium falciparum infection can become malignant and fatal if untreated, making it the most dreaded form of malaria.