Question

Which of the following stage of malarial parasite is not found in the vector
A. Ookinete
B. Sporozoite
C. Merozoite
D. Zygote

Answer 1

Hint: Malaria is the cyclic infection of humans and female Anopheles mosquitoes. In humans the malarial parasite grows and first multiplies in the hepatocytes i.e. in liver cells and after that in the red blood cells.

Complete Answer:
Life cycle of malarial parasite:
- Malaria is caused by Plasmodium. Life cycle of the malarial parasite involves two hosts – human and female Anopheles mosquitoes.
- In humans – A malarial infected female Anopheles mosquito inoculates sporozoites into the human host. Sporozoites infect the human liver cell first and mature into the schizonts.
- After that liver cells get disrupted and release merozoites. After this infection, the parasite undergo asexual multiplication in the red blood cells.
- Merozoites infect red blood cells. The ring stage trophozoites mature into schizonts which rupture the red blood cell and release merozoites.
- Some parasites differentiate into sexual erythrocytic stages (gametocytes).

In female Anopheles mosquito:
- The male and female gametocytes are ingested by the female Anopheles mosquito during a blood meal.
- The multiplication of parasites in the mosquito is called the sporogonic cycle.
- In the stomach of the mosquito, the fusion of both the gametes takes place which result in the zygote.
- The zygote inturn becomes motile and elongated and called as Ookinetes. Ookinetes invade the midgut wall of the mosquito where they develop into the oocysts.
- The oocysts grow, rupture and release sporozoites which make their way to the mosquito’s salivary glands.
- Mosquitoes inoculate sporozoites into the human body during a blood meal.

Hence, option C is the correct option for this question.

Note: The blood stage parasite causes the symptoms of malaria. The symptoms of malaria include chills, fever and sweating. These symptoms occur a few weeks after being eaten by female Anopheles mosquitoes.