Causative agent of Q-fever –
**Core Concept**
Q-fever is a zoonotic disease caused by a bacterium that affects animals and humans. The causative agent of Q-fever is a type of bacteria that is typically found in the tissues of animals, particularly sheep, goats, and cattle.
**Why the Correct Answer is Right**
The causative agent of Q-fever is *Coxiella burnetii*, a gram-negative bacterium that is highly infectious and can survive for long periods outside of a host. *C. burnetii* is usually transmitted to humans through inhalation of dust or aerosols contaminated with the bacteria, often from infected animal tissues or products. The bacteria can also be transmitted through contact with infected animals or contaminated materials.
**Why Each Wrong Option is Incorrect**
*Option A:* *Francisella tularensis* is the causative agent of tularemia, not Q-fever. **Option B:** *Bartonella henselae* causes cat-scratch disease, which is not related to Q-fever. **Option C:** *Brucella abortus* causes brucellosis, a different zoonotic disease.
**Clinical Pearl / High-Yield Fact**
Remember that Q-fever can be transmitted through inhalation of contaminated dust or aerosols, and that the bacteria can survive for long periods outside of a host, making it a highly infectious disease.
**Correct Answer: D. Coxiella burnetii**