This treatise is intended to provide the students of Parasitology, Microbiology and Medicine with the latest information on parasitic and zoonotic diseases. Since the last few years, a number of such diseases, such as encephalitis, dengue, chikungunya, SARS, avian influenza viral haemorrhagic fever, anthrax, etc. have broken out as epidemic in several countries of the world which have triggered the realisation that human, animal and environmental health are intertwined. The book consists of an introductory part, where the concept of parasitism and the terms used by parasitologists have been presented.