Intestinal nematodes are a type of roundworm that inhabit the gastrointestinal tract of humans and animals. They are a significant cause of parasitic infections worldwide, leading to various health issues such as malnutrition, anemia, and gastrointestinal discomfort. Common species include Ascaris lumbricoides, Trichuris trichiura, and Ancylostoma duodenale. These parasites are typically transmitted through contaminated food, water, or soil. Once ingested, they can grow and reproduce within the intestines, causing symptoms that may range from mild to severe. Effective treatments often involve antiparasitic medications, along with improved sanitation and hygiene practices to prevent infection.