There are different types of intestinal worms like roundworms, tapeworms and hookworms. When an infected person defecates outside of a latrine the worms' eggs left on the soil can stick to food, hands and vegetables. Touching or eating such contaminated food (without washing hands) will lead to infection. If untreated worms can lead to anaemia, development problems in children and low birth weight in babies born to infected mothers. Children and adults should take deworming medicine regularly to avoid infection.
Attribution: Straight Talk Foundation