The reason of spore disease in animals is :

Options

A. Bacteria
B. Insects
C. Protozoa
D. Virus

Explanation

**Step-by-Step Solution:**

1. **Understanding Spore Disease**:
- Spore diseases in animals are caused by specific pathogens. It's important to identify which type of pathogen is responsible for these diseases.

2. **Identifying the Options**:
- The options given are:
a) Bacteria
b) Insect
c) Protozoa
d) Virus

3. **Analyzing Each Option**:
- **Bacteria**: While some diseases in animals are caused by bacteria, they do not typically form spores in the same way that some pathogens do.
- **Insect**: Insects can be vectors for diseases but do not cause spore diseases directly.
- **Protozoa**: Protozoa can cause diseases in animals, but they are not known for forming spores.
- **Virus**: Viruses are known to cause spore diseases in animals. They can lead to severe health issues and often have no cure.

4. **Conclusion**:
- Based on the analysis, the correct answer to the question "The reason of spore disease in animals is:" is **D) Virus**.

5. **Importance of Vaccination**:
- It is crucial for animals to receive vaccinations to prevent spore diseases, as there is often no cure once the disease has manifested.