18. Ascarias Worm
Image Source: Medical News Today
People are generally aware of tapeworms and roundworms, but not everybody has a grasp of their danger. In this case, the Ascarias Worm is a lethal killer. The roundworm does its damage by infecting the hosts’ small intestine. According to the WHO, the Ascarias Worm kills an average of 2,500 people per year.