1The removal of parasitic or symbiotic protozoans or invertebrates from a host organism or a part of its body, specifically the elimination of the ciliate protozoan population in the rumen of a ruminant; an instance of this.
2Destruction or loss of (part of) the animal life of a region, habitat, etc.; an instance of this.
1920s. From de- + fauna + -ation, after depopulation.