**Core Concept**
Hansens disease, also known as leprosy, is a chronic bacterial infection caused by Mycobacterium leprae that primarily affects the peripheral nerves, skin, and mucous membranes. The disease leads to a progressive destruction of the peripheral nerves, resulting in a loss of sensation and motor function.

**Why the Correct Answer is Right**
The earliest sensation to be lost in Hansens disease is typically pain and temperature sensation. This is due to the involvement of the small fibers of the peripheral nerves, which are responsible for transmitting pain and temperature sensations. The leprosy bacillus primarily infects the Schwann cells, which are responsible for myelinating the peripheral nerves. The destruction of these cells leads to demyelination and the loss of nerve conduction, resulting in the loss of pain and temperature sensation.

**Why Each Wrong Option is Incorrect**
**Option A:** Touch is typically preserved until late in the disease, as the larger nerve fibers responsible for transmitting touch sensation are affected later in the disease.
**Option B:** Vibration and position sense are typically lost later in the disease, as the larger nerve fibers responsible for transmitting these sensations are affected later in the disease.
**Option C:** Proprioception is typically preserved until late in the disease, as the larger nerve fibers responsible for transmitting proprioception are affected later in the disease.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the loss of sensation in Hansens disease can be patchy and irregular, making it difficult to diagnose. A thorough examination of the skin and peripheral nerves, as well as a detailed history, is crucial in diagnosing this disease.

**Correct Answer: A. Pain and temperature sensation.**