Causative organism of Weil disease is:
**Weil's Disease**
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**Core Concept**
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Weil's disease, also known as leptospirosis, is a zoonotic infection caused by the bacterium *Leptospira*. It is transmitted through contact with contaminated water, soil, or food, and can lead to severe complications if left untreated.
**Why the Correct Answer is Right**
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The causative organism of Weil's disease is *Leptospira*, a genus of spirochetes that infects humans and animals. *Leptospira* is a highly adaptable bacterium that can survive in a variety of environments, including water and soil, making it a significant public health concern. The bacteria enter the body through cuts or abrasions in the skin, or through mucous membranes, and can cause a range of symptoms from mild to severe.
**Why Each Wrong Option is Incorrect**
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* **Option A:** *Borrelia burgdorferi* is the causative organism of Lyme disease, a different tick-borne illness.
* **Option B:** *Francisella tularensis* is the causative organism of tularemia, a zoonotic infection caused by contact with infected animals or contaminated water.
* **Option D:** *Bacillus anthracis* is the causative organism of anthrax, a bacterial infection caused by contact with contaminated animal products.
**Clinical Pearl / High-Yield Fact**
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Weil's disease is often referred to as "swamp fever" due to its historical association with outbreaks in areas with high water tables and poor sanitation. It is essential to consider Weil's disease in the differential diagnosis of patients presenting with fever, headache, and muscle aches, especially after exposure to contaminated water or soil.
**Correct Answer: C. Leptospira.**