Exo-erythrocytic cycle is absent in

Options

A. P. ovale
B. P. vivax
C. Both A and B
D. P. falciparum.

Answer

To answer the question regarding which species of Plasmodium lacks the exo-erythrocytic cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Life Cycle of Plasmodium**:
- Plasmodium is a genus of parasitic protozoa known to cause malaria. The life cycle involves two hosts: the female Anopheles mosquito (the primary host) and humans (the secondary host).

2. **Identify the Stages of the Life Cycle**:
- The life cycle includes several stages:
- **Sporozoite Stage**: This is the infective stage that enters the human body through the bite of an infected mosquito.
- **Pre-erythrocytic Cycle**: After entering the human body, sporozoites travel to the liver and infect liver cells.
- **Exo-erythrocytic Cycle**: This stage occurs in the liver, where the sporozoites multiply and form cryptozoites and metacryptozoites.
- **Erythrocytic Cycle**: Finally, the metacryptozoites enter the red blood cells (RBCs) and continue to multiply, leading to the symptoms of malaria.

3. **Determine the Species of Plasmodium**:
- There are several species of Plasmodium, including:
- **Plasmodium falciparum**
- **Plasmodium vivax**
- **Plasmodium ovale**
- **Plasmodium malariae**
- Among these, Plasmodium falciparum is known for its virulence and is the most fatal type of malaria.

4. **Identify the Absence of Exo-erythrocytic Cycle**:
- In the case of Plasmodium falciparum, it does not undergo the exo-erythrocytic cycle. Instead, it directly enters the erythrocytic cycle after the pre-erythrocytic stage.
- On the other hand, Plasmodium vivax and Plasmodium ovale do have an exo-erythrocytic cycle, where they multiply in the liver before entering the RBCs.

5. **Conclusion**:
- Therefore, the species of Plasmodium that lacks the exo-erythrocytic cycle is **Plasmodium falciparum**.

### Final Answer:
**Plasmodium falciparum** is the species in which the exo-erythrocytic cycle is absent.