ThePigSite Pig Health
Introduction(489) A parasite is an organism that at some stage must live on or within its host to survive. The relationship is usually a disadvantage for the host but occasionally it may be beneficial in which case it is called a symbiotic relationship (symbiosis).
In its broadest sense this definition would include bacteria and viruses but the term "Parasites" as used commonly in veterinary medicine excludes these. Technically, the parasites dealt with in this chapter are all part of the animal kingdom and the cells of their bodies have true distinct nuclei whereas bacteria are members of the plant kingdom and their cells lack a true distinct nuclei. Viruses are defined differently.
Parasites in the pig are classified into two groups, internal (endoparasites) which live inside the body and external (ectoparasites) which live on or in the skin. They are generally host specific but there are exceptions.