Epidemiology studies how often and why diseases occur in different groups of people. Epidemiological information is used to plan and evaluate disease prevention strategies and to guide the treatment of patients who already have the disease.
Parasitology is the branch of science that deals with parasites and parasitic worms. Parasitism is a form of symbiosis in which one organism (called the parasite) benefits at the expense of another organism, usually a different species (called the host). This compound can also cause damage to the host. An example of parasitism is the association of a parasitic tapeworm with its vertebrate host.
Parasitology has different sub-disciplines: