The element is a clause if there is a subject and a verb, and it is a phrase if both of these parts of speech are not present. What comes after the introductory element is always an independent clause, or complete sentence, on its own, and the introductory element gives meaning to it.
A parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host. There are three main classes of parasites that can cause disease in humans: protozoa, helminths, and ectoparasites.
Wormlike parasites are called helminths. Worms usually live in the gastrointestinal tract. Common worms include roundworms, tapeworms and hookworms. Infection is usually more common in areas with poor sanitation, poor personal hygiene, or where human faeces are used as fertiliser.