Which of the following are protozoan diseases that are transmitted by mosquito vectors?

Options

A. Filariasis and typhus
B. Kala-azar and diphtheria
C. Malaria and kala-azar
D. Yellow fever and dengue fever

Explanation

To solve the question regarding which protozoan diseases are transmitted by mosquito vectors, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify diseases caused by protozoa that are transmitted by mosquitoes.

2. **Evaluate the First Option (Phallorhesis and Typhus)**:
- **Phallorhesis**: This disease is caused by nematodes (roundworms), not protozoa.
- **Typhus**: This disease is caused by bacteria (Rickettsia prowazekii).
- **Conclusion**: This option is incorrect.

3. **Evaluate the Second Option (Kala Azar and Diphtheria)**:
- **Kala Azar**: This disease is caused by the protozoan Leishmania, which is transmitted by sandflies, not mosquitoes.
- **Diphtheria**: This disease is caused by bacteria (Corynebacterium diphtheriae).
- **Conclusion**: This option is incorrect.

4. **Evaluate the Third Option (Malaria and Chlamydia)**:
- **Malaria**: This disease is caused by the protozoan Plasmodium and is transmitted by Anopheles mosquitoes.
- **Chlamydia**: This is caused by bacteria (Chlamydia trachomatis).
- **Conclusion**: Although malaria is a protozoan disease transmitted by mosquitoes, Chlamydia is not. Therefore, this option is partially correct but not fully.

5. **Evaluate the Fourth Option (Yellow Fever and Dengue Fever)**:
- **Yellow Fever**: This is caused by a virus and transmitted by mosquitoes.
- **Dengue Fever**: This is also caused by a virus and transmitted by mosquitoes.
- **Conclusion**: This option is incorrect.

6. **Final Conclusion**: The only protozoan disease transmitted by mosquitoes is **Malaria**. Therefore, the correct answer is that **Malaria** is the only protozoan disease listed that is transmitted by mosquitoes.