160. Which form of the plasmodia is transmitted from mosquito to human?
A. Sporozoite
B. Gametocyte
C. Merozoite
D. Hypnozoite

Introduction to Plasmodium and Malaria

Malaria, caused by the Plasmodium parasite, remains a significant global health issue, particularly in tropical regions. The life cycle of Plasmodium involves multiple stages, both within the mosquito vector and the human host. One of the critical steps in this cycle is the transmission of the parasite from the mosquito to humans, which leads to the onset of malaria infection.

Understanding the form of Plasmodium that is responsible for initiating the infection in humans is crucial for developing effective prevention and treatment strategies.

The Lifecycle of Plasmodium: From Mosquito to Human

Plasmodium undergoes a complex lifecycle involving both mosquitoes and humans as hosts. Here’s a breakdown of the key stages:

1. Sporozoite Stage:

   • When an infected Anopheles mosquito bites a human to take a blood meal, it injects sporozoites into the bloodstream. These sporozoites are the form of Plasmodium that initiates infection in humans.

   • Once in the bloodstream, sporozoites travel quickly to the liver, where they infect liver cells and begin to multiply.

2. Gametocyte Stage:

   • Infected humans also harbor gametocytes (the sexual form of the parasite). When another mosquito bites an infected human, it picks up these gametocytes.

   • Inside the mosquito, the gametocytes mature into gametes, which then fertilize to form a zygote, eventually developing into sporozoites again, completing the cycle.

3. Merozoite Stage:

   • After the sporozoites invade liver cells, they mature into merozoites, which are released into the bloodstream. These merozoites infect red blood cells, leading to the symptoms of malaria.

4. Hypnozoite Stage:

   • In certain species of Plasmodium (e.g., Plasmodium vivax), some of the liver-stage parasites may remain dormant in the liver as hypnozoites, potentially causing relapses of malaria after some time.

The Correct Answer

The form of Plasmodium that is transmitted from the mosquito to humans is the sporozoite.

A. Sporozoite

Sporozoites are the infective form of the parasite and are introduced into the human bloodstream during the mosquito’s bite. Once in the blood, sporozoites travel to the liver to begin the next stage of the lifecycle.

Conclusion

The sporozoite is the key form of Plasmodium responsible for initiating malaria in humans. Understanding this stage is essential for developing targeted interventions, such as vaccines or mosquito control measures, to prevent malaria transmission