Question

Explain the life cycle of Plasmodium (Malaria) and the role of the female Anopheles mosquito.

Hint:

The life cycle of \textit{Plasmodium} involves two hosts: humans (asexual reproduction) and the female \textit{Anopheles} mosquito (sexual reproduction). The infective stage transmitted to humans is the sporozoite.

Answer 1

Concept: Malaria is a serious infectious disease caused by the protozoan parasite \textit{Plasmodium}. The parasite completes its life cycle in two hosts: humans and the female \textit{Anopheles} mosquito. Humans serve as the intermediate host where asexual reproduction occurs, while the female \textit{Anopheles} mosquito acts as the definitive host where sexual reproduction takes place.
Step 1:Infection of Humans.
The life cycle begins when an infected female \textit{Anopheles} mosquito bites a human and injects the infective stage of the parasite called sporozoites into the bloodstream. These sporozoites quickly travel to the liver.

• In the liver cells, the sporozoites multiply asexually and develop into merozoites.
• After multiplication, the liver cells burst and release merozoites into the bloodstream.

Step 2:Infection of Red Blood Cells.
The released merozoites invade red blood cells (RBCs).

• Inside RBCs, the parasite grows and divides repeatedly.
• The infected RBCs eventually rupture, releasing more merozoites into the blood.
• This repeated rupture of RBCs causes symptoms of malaria such as fever and chills.

Some merozoites differentiate into sexual forms known as gametocytes.
Step 3:Entry into the Mosquito.
When a female \textit{Anopheles} mosquito bites an infected person, it ingests blood containing gametocytes.

• Inside the mosquito's gut, the gametocytes develop into male and female gametes.
• Fertilization occurs, forming a zygote.
• The zygote develops into a motile structure called an ookinete.

Step 4:Formation of Sporozoites in the Mosquito.
The ookinete penetrates the stomach wall of the mosquito and forms an oocyst.

• Inside the oocyst, numerous sporozoites are produced.
• When the oocyst bursts, sporozoites are released and migrate to the salivary glands of the mosquito.

These sporozoites are then ready to infect another human host during the next mosquito bite.
Step 5:Role of Female Anopheles Mosquito.
The female \textit{Anopheles} mosquito plays a crucial role in the transmission of malaria.

• It acts as the definitive host where sexual reproduction of \textit{Plasmodium} occurs.
• It transmits the infective stage (sporozoites) to humans through its bite.
• Only the female mosquito feeds on blood because it requires proteins for egg development.

Thus, the female \textit{Anopheles} mosquito is responsible for spreading malaria from one person to another.