**Core Concept**
Direct zoonoses are diseases that can be directly transmitted from animals to humans without the need for a vector. This includes diseases caused by **bacteria**, **viruses**, and **parasites**. The key concept here is the direct transmission of a pathogen from an animal host to a human host.

**Why the Correct Answer is Right**
Rabies is a viral disease that is transmitted through the saliva of infected animals, typically through a bite. This direct transmission makes rabies a classic example of a direct zoonosis. The **rabies virus** attacks the central nervous system, leading to severe neurological symptoms and almost always resulting in death if not promptly treated after exposure.

**Why Each Wrong Option is Incorrect**
**Option B:** Brucellosis is indeed a zoonosis but is usually transmitted to humans through contact with infected animal tissues or consumption of contaminated animal products, not exclusively direct contact.
**Option C:** Taeniasis is a parasitic infection caused by tapeworms, transmitted to humans through the ingestion of contaminated food, not direct animal-to-human contact.
**Option D:** Hydatid disease, caused by the **Echinococcus** parasite, is also transmitted through the fecal-oral route, often involving contaminated food or water, rather than direct animal-to-human transmission.

**Clinical Pearl / High-Yield Fact**
Remember, direct zoonoses like rabies require immediate medical attention if exposure occurs, highlighting the importance of prompt post-exposure prophylaxis to prevent the disease.

**Correct Answer:** a) Rabies