Question

Represent schematically the life cycle of a malarial parasite.

Answer 1

Life cycle of Plasmodium

Plasmodium is digenetic parasite. It needs two hosts, man and female Anopheles mosquito, to complete its life cycle. The asexual phase occurs in man while the sexual phase occurs in the female Anopheles mosquito.

In man

• Man gets infected when female Anopheles bites to take the blood meal. The infectious stage is sporozoite.
• The sporozoites enter the liver cells where they multiply asexually.
• After release from the liver cells, they enter RBCs where gametocytes are formed.
• The rupturing of the RBCs to release gametocytes produces toxins (hemozoin) which causes fever.

In female Anopheles

• Female Anopheles mosquitoes take the gametocytes along with the blood meal.
• Fertilisation takes place in the stomach of the mosquito, forming the zygote.
• The zygote forms ookinete, which pierces the wall of the stomach and changes into oocyst.
• The infectious sporozoite is present in the oocyst which is released and enters the salivary glands of the mosquito.
• On biting a healthy person, infectious sporozoites are transmitted.