When you think of the Helminths … think worms. These parasites, unlike the Protozoa, are parasites that can generally be seen without the use of a microscope.
They are probably the most common parasites infecting humans and depending on the worm, are capable of infecting all organs or organ systems in the human body. It’s important to note that each parasitic worm has its own characteristic biology, epidemiology, and pathogenicity. The transmission of the Helminths can occur through water, soil, food, and vectors such as arthropods and mollusk. Transmission is a unique characteristic to each genus and species.
There are three main groups within the Helminths. They can be basically separated by their phenotypic appearance.
Nematodes – called roundworms because when sliced longitudinally they are circular in shape
Cestodes – called tapeworms because most of them have a tape appearance to them
Trematodes – called flukes or flat worms due to their flat whole body shape.