Which of the following is a viral disease of poultry Birds?

Options

A. Coccidiosis
B. Spirochaetosis
C. new castle's disease
D. Encephalomalacia

Answer

To determine which of the following is a viral disease of poultry birds, we will analyze each option provided:

1. **Causidiosis**: This disease is caused by protozoa, specifically a type that affects the intestines of poultry birds. Since it is not caused by a virus, this option is incorrect.

2. **Spirochetosis**: This disease is caused by bacteria, which also affect the intestines of poultry birds. As it is bacterial and not viral, this option is also incorrect.

3. **Newcastle's disease**: This disease is caused by a virus known as Paramyxovirus. It primarily affects poultry birds, leading to symptoms such as fever and decreased activity. This option is correct as it is a viral disease.

4. **Encephalomalacia**: This condition is related to the central nervous system and can be associated with brain or heart defects. It is not specifically a viral disease affecting poultry birds, making this option incorrect.

Based on the analysis, the correct answer to the question "Which of the following is a viral disease of poultry birds?" is **Newcastle's disease**.

### Step-by-Step Solution:
1. Identify the diseases listed: Causidiosis, Spirochetosis, Newcastle's disease, and Encephalomalacia.
2. Determine the causative agents of each disease:
- Causidiosis: Caused by protozoa.
- Spirochetosis: Caused by bacteria.
- Newcastle's disease: Caused by a virus (Paramyxovirus).
- Encephalomalacia: Related to the central nervous system, not specifically viral.
3. Evaluate which disease is caused by a virus: Newcastle's disease is the only one that fits this criterion.
4. Conclude that the correct answer is Newcastle's disease.