1.1 Introduction to Parasitology and Its Terminology 1.1.1 Parasites Parasites are organisms which live in or on another organism, drawing suste- nance from the host and causing it harm. These include animals, plants, fungi, bacteria, and viruses, which live as host-dependent guests. Parasitism is one of the most successful and widespread ways of life. Some authors estimate that more than 50% of all eukaryotic organisms are parasitic, or have at least one parasitic phase during their life cycle. There is no complete biodiversity inventory to verify this assumption; it does stand to reason, however, given the fact that parasites live in or on almost every multicellular animal, and many host species are infected with several parasite species specifically adapted to them. Some of the most important human parasites are listed in Table 1.1. The term parasite originated in Ancient Greece. It is derived from the Greek word “parasitos” (Greek pará = on, at, beside; sítos = food). The name parasite was first used to describe the officials who participated in sacrificial meals on behalf