Which of the following has only one host ?

Options

A. P. vivax
B. Trypanosoma gambiense
C. Taenia solium
D. Entamoeba histolytica.

Answer

To determine which of the given organisms has only one host, we will analyze each option one by one.

### Step-by-Step Solution:

1. **Identify the Organisms**: The options provided are:
- Plasmodium vivax
- Trypanosoma gambiense
- Tinea solium
- Entamoeba histolytica

2. **Analyze Plasmodium vivax**:
- Plasmodium vivax is a protozoan parasite that causes malaria.
- It requires two hosts to complete its life cycle: the female Anopheles mosquito (where sexual reproduction occurs) and humans (where asexual reproduction occurs).
- **Conclusion**: Plasmodium vivax has two hosts.

3. **Analyze Trypanosoma gambiense**:
- Trypanosoma gambiense is a protozoan parasite that causes sleeping sickness.
- It is transmitted by the tsetse fly (primary host) and infects humans and animals (secondary hosts).
- **Conclusion**: Trypanosoma gambiense also has two hosts.

4. **Analyze Tinea solium**:
- Tinea solium is a parasitic worm (tapeworm) that causes taeniasis.
- Its definitive host is humans, but it can also infect pigs (intermediate host).
- **Conclusion**: Tinea solium has two hosts.

5. **Analyze Entamoeba histolytica**:
- Entamoeba histolytica is an anaerobic protozoan that causes amoebic dysentery.
- It primarily infects humans and does not require any other host to complete its life cycle.
- **Conclusion**: Entamoeba histolytica has only one host.

6. **Final Answer**:
- Based on the analysis, the organism that has only one host is **Entamoeba histolytica**. Therefore, the correct answer is option D.