filariasis is caused by

Options

A. Dead adult filariae
B. Presence of bacteria in filarial wall
C. Microfilariae
D. Biting of filarial worm

Answer

**Step-by-Step Solution:**

1. **Understanding Filariasis**: Filariasis is a parasitic disease caused by infections with filarial worms. These worms are thread-like and belong to the group of nematodes.

2. **Identifying the Causative Agents**: The disease is primarily caused by three species of filarial worms: Wuchereria bancrofti, Brugia malayi, and Brugia timori. These worms are typically found in the lymphatic system of humans.

3. **Examining the Options**:
- **Option 1: Dead adult filaria** - This is incorrect because the disease is not caused by dead worms; it is caused by living adult worms.
- **Option 2: Presence of bacteria in filarial wall** - This option is also incorrect. Filariasis is a parasitic infection, not caused by bacteria.
- **Option 3: Microfilaria** - While microfilaria are the larval stage of the filarial worms, they are not the direct cause of the disease itself.
- **Option 4: Biting of filarial worm** - This is the correct answer. Filariasis is transmitted through the bites of infected mosquitoes, which introduce the larvae into the human host.

4. **Conclusion**: Therefore, the correct answer to the question "Filariasis is caused by" is the biting of filarial worms.

**Final Answer**: Filariasis is caused by the biting of filarial worms.

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