Question

Sexual stage of $Plasmodium$ occurs in

• A.
  Intestine of mosquito
• B.
  Salivary glands of mosquito
• C.
  Human liver
• D.
  Human RBC

Answer 1

The correct option is D

Human RBC
Malaria- Causative agent

• The protozoa, $Plasmodium$, causes malaria.
• The pathogen is carried by the vector, female $Anopheles$ mosquito.
• It is transmitted to healthy individuals through its bite.

Life cycle of $Plasmodium$

• $Plasmodium$ enters the human body as sporozoites (immature form) through the bite of an infected female $Anopheles$ mosquito.
• These parasites are carried to the hepatocytes (liver cells) by blood. They multiply asexually in the liver cells and get matured to form schizonts.
• The schizonts again undergo multiplication to form thousands of merozoites.
• The accumulated merozoites escape the liver cells and reenter the bloodstream. There, they affect the RBCs by invading, dividing and destroying them.
• Few of the merozoites present in the RBCs develop into sexual stage called gametocytes inside the RBCs.
• When a female $Anopheles$ mosquito bites an infected person, it takes in the $Plasmodium$ gametocytes along with the blood meal.
• The male and the female gametocytes fuse in the gut of the mosquito i.e., they reproduce sexually to form zygote followed by the embryonic forms (ookinetes). This matures into oocysts which then liberate thousands of sporozoites from the mosquito’s gut.
• The sporozoites then enter the salivary glands of the mosquito.
• The mosquito injects the sporozoites into uninfected humans and the cycle continues.

Final answer:

b. Human RBC