Ascaris

Ascaris is a genus of parasitic roundworms found in the intestines of vertebrates. They are among the largest and most common species of parasitic worms, and can reach lengths of up to 35 cm (14 in). Ascaris lumbricoides, the most common species, is a human parasite responsible for the disease ascariasis. Ascaris worms have a thick cuticle, or outer covering, and a simple digestive system with a single opening for both ingestion and elimination. The worms attach to the intestinal wall with a muscular body and suck nutrients from their host. They reproduce sexually, with eggs being passed in the host's feces. These eggs are ingested by humans or animals, and the larvae hatch in the small intestine and mature into adult worms. Symptoms of ascariasis include abdominal pain, nausea, and vomiting. Treatment includes medications to kill the worms and improve nutrition.