From the Latin invasio - invasion, attack.

Invasion is a term meaning the infestation of an organism by parasitic animals. Often Invasion is one of the concepts of acclimatization, meaning the invasion of a body of water by organisms of a new species.

The penetration of parasites (protozoa, worms, arthropods) into the body of animals with the subsequent development of a complex pathophysiological process of their interaction, which may occur in the form of asymptomatic carriage or clinically expressed invasive disease.