The infective stage of Ascaris is

Options

A. Fertilized egg
B. Embryonated egg
C. Rhabditoid larva
D. Adult Ascaris

Answer

To determine the infective stage of Ascaris, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Ascaris**: Ascaris is a type of roundworm that infects humans. It is important to note that it is monogenetic, meaning it has only one host and does not require an intermediate host for its life cycle.

2. **Life Cycle of Ascaris**: The life cycle of Ascaris involves the development of eggs into larvae. The eggs undergo cleavage, which is a process of cell division. The cleavage in Ascaris is spiral, determinate, and holoblastic.

3. **Larval Stages**: After the eggs are fertilized, they develop into larvae. The first larval stage that forms is called the rhabditiform larva, which occurs around 10 to 14 days after cleavage. However, this stage is not the infective stage.

4. **Infective Stage Identification**: After the rhabditiform larva, the larvae undergo further development and transform into the second larval stage. This second larval stage is capable of causing infection and is known as the infective stage.

5. **Infection Process**: Humans acquire the infection by ingesting the embryonated eggs of Ascaris. Once ingested, the eggs hatch in the small intestine, releasing the larvae that penetrate the intestinal wall and migrate through the body, eventually reaching the lungs.

6. **Conclusion**: Among the options provided (fertilized egg, embryonated egg, rhabditiform larva, and adult Ascaris), the correct answer is the **embryonated egg**, as it is the infective stage of Ascaris.

### Final Answer:
The infective stage of Ascaris is the **embryonated egg**.

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