Zoology is the study of animals. It can include the classifications of animals into groups (e.g. animals with backbone and animals without backbone, and the sub-grouping (and sub-sub-grouping) of those); it can include studying how animal bodies work, how animals evolved, behaviour of animals, animals and their environments. And it cover a range of animals from the very basic sponges in the sea (yes, they are animals!) to insects to frogs to fluffy lions.
Studying of parasites, as I know it, was included in Zoology too and it’s counted as applied zoology.