Human RoundwormAscaris lumbricoides, the large human roundworm, is the most massive nematode to parasitize humans, growing up to 16 inches (40 centimeters) long and often as thick as a pencil. Infections of this intestinal roundworm, called ascariasis, are extremely common in rural communities around the world and affect as many as 1.5 billion people, almost one-quarter of the world's population. |