Parasitic worms

Worms that live inside a person or animal, their host, and feed on it: the roundworm and pinworm in the gut, the hookworm that sucks blood, the tapeworm, and the dog tapeworm whose eggs can grow into water-filled cysts in the liver. Most lay eggs that leave in faeces; they reach the next person on unwashed vegetables, in dirty water, on unwashed hands, in undercooked meat, or, for hookworm, through bare feet in damp soil. Washing hands and vegetables, cooking meat through, wearing shoes and keeping sewage away from water break the cycle.