Ascariais is caused by Round worms. These belong to Phylum Aschelminthes. These are known as roundworms as they show presence of body cavity. These show well presence of organ system and hence digestive system is also complete. These can be free living or parasitic in nature. The parasites can be in ectoparasites or endoparasites depending on whether they are on the host or inside the host. In humans these cause intestinal infections. These block the passage of intestine as a result of which internal bleeding, muscle cramps, fever occurs.