Organism most likely to cause “fever of unknown origin” in a farmer who raises goats –
**Core Concept**
The "fever of unknown origin" (FUO) refers to a prolonged fever lasting more than three weeks without a clear diagnosis. In a farmer who raises goats, the underlying cause could be an occupational exposure to zoonotic pathogens, which are organisms transmitted from animals to humans.
**Why the Correct Answer is Right**
Q fever, caused by *Coxiella burnetii*, is a zoonotic disease that can be transmitted to humans through inhalation of aerosolized bacteria from infected animal tissues, such as goat placenta. This bacterium is highly contagious and can survive in a dormant state outside the host. In individuals with occupational exposure to infected animals, Q fever can manifest as FUO due to its insidious onset and lack of specific symptoms.
**Why Each Wrong Option is Incorrect**
* **Option A:** Brucellosis, caused by *Brucella* spp., is another zoonotic disease that can be transmitted to humans through contact with infected animal tissues. However, it typically presents with symptoms such as fever, sweating, and joint pain, making it less likely to be considered a FUO.
* **Option B:** Anaplasmosis, caused by *Anaplasma phagocytophilum*, is a tick-borne disease that can cause fever, headache, and muscle pain. While it can be transmitted to humans through tick bites, it is less likely to be associated with FUO in a farmer with occupational exposure to goats.
* **Option C:** Leptospirosis, caused by *Leptospira* spp., is a zoonotic disease that can be transmitted to humans through contact with contaminated water or soil. It typically presents with symptoms such as fever, headache, and muscle pain, making it less likely to be considered a FUO.
**Clinical Pearl / High-Yield Fact**
Q fever is often referred to as the "great mimicker" due to its nonspecific symptoms, which can resemble those of other infectious and non-infectious diseases. It is essential to consider Q fever in the differential diagnosis of FUO in individuals with occupational exposure to infected animals.
**Correct Answer: C. Leptospirosis is less likely to be the correct answer. The correct answer is likely D. Q fever. However, D is missing so the correct answer is actually not present in the options.