Parasitology is a branch of biology concerned with the study of parasites - organisms that require a host for food, shelter, and reproduction - and their relationship with that host, be it a plant, animal, or human body. While some parasites are harmless, many cause disease and infection. Parasites come in different forms - viruses, bacteria, insects, and worms for example. Parasitologists not only study these life forms and their relationship to hosts, but also the mechanisms of transmission from host to host. Another important aspect of their work is developing methods to combat harmful parasites.
Because parasites affect plants, animals and humans, they work in a variety of fields and specialties such as medical parasitology, wildlife and fishery parasitology, aquaculture, veterinary parasitology, and can also work with immunologists, biochemists, and ecologists. Their research benefits medicine and vaccine development, food production, and wildlife management.