Ascaris is a genus of parasitic roundworms that primarily infects the intestines of humans and other animals. The most common species, Ascaris lumbricoides, can grow up to 35 centimeters long. These worms are transmitted through contaminated food or water, leading to infections known as ascariasis. Once ingested, Ascaris larvae hatch in the intestines and migrate through the bloodstream to the lungs before returning to the intestines to mature. Symptoms of ascariasis can include abdominal pain, malnutrition, and respiratory issues. Proper sanitation and hygiene practices are essential to prevent infection.