Which of the following sexually transmitted diseases is caused by a protozoan ?

Options

A. Trichomoniasis
B. Chlamydiasis
C. Gonorrhoea
D. Syphilis

Answer

To determine which sexually transmitted disease (STD) is caused by a protozoan, we can analyze the options provided:

### Step-by-Step Solution:

1. **Identify the Options**: We need to look at the list of sexually transmitted diseases provided in the question. The first option is trichomoniasis, the second is chlamydiasis, the third is gonorrhea, and the fourth is syphilis.

2. **Examine Trichomoniasis**:
- Trichomoniasis is also known as vaginitis or leucoria.
- The causative organism is **Trichomonas vaginalis**, which is a protozoan.
- Symptoms include burning sensation, itching, and frothy discharge.

3. **Examine Chlamydiasis**:
- Chlamydiasis is caused by **Chlamydia trachomatis**, which is not a protozoan but an intracellular bacterium.
- Therefore, this option is incorrect.

4. **Examine Gonorrhea**:
- Gonorrhea is caused by **Neisseria gonorrhoeae**, which is a bacterium.
- Symptoms include painful urination and discharge of pus.
- Hence, this option is also incorrect.

5. **Examine Syphilis**:
- Syphilis is caused by **Treponema pallidum**, which is a spirochete (a type of bacterium).
- It has different stages with varying symptoms.
- This option is incorrect as well.

6. **Conclusion**: After analyzing all the options, we find that the only sexually transmitted disease caused by a protozoan is **trichomoniasis**.

### Final Answer:
The sexually transmitted disease caused by a protozoan is **Trichomoniasis**.

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