Parasitology

The infective stage of Ascaris is the second-stage larva. After hatching from the fertilized eggs, the larvae undergo development, and the second-stage larva is the one capable of infecting the host.
- First-stage larvae are not infective.
- Third-stage larvae appear in some nematodes but not Ascaris.
- Fertilized eggs are the transmission stage but require development into larvae to become infective.