The study of parasites and their hosts is referred to as parasitology. It also includes the study of the relationship between them. It is a biological field that draws on techniques from various fields such as bioinformatics, biochemistry, cell biology, genetics, ecology, immunology, molecular biology and evolution. Some of the branches of parasitology are medical parasitology, veterinary parasitology and structural parasitology. Medical parasitology deals with the parasites that infect humans and the diseases caused by them. It also focuses on various methods used to diagnose, prevent, control and treat such diseases. The study of parasites that leads to economic losses in agriculture and aquaculture operations infecting the companion animals fall under veterinary parasitology. This book explores all the important aspects of parasitology in the present day scenario. It aims to shed light on some of the unexplored aspects of this field. This book will serve as a valuable source of reference for those interested in this field.